Shallow water infrastructure needs to support increased activity on the shores of Semarang.This study chooses several pontoons because of their good stability,rolling motion,and more expansive space.A coupled simulati...Shallow water infrastructure needs to support increased activity on the shores of Semarang.This study chooses several pontoons because of their good stability,rolling motion,and more expansive space.A coupled simulation method consisting of hydrodynamic and structural calculations has been used to evaluate a catamaran pontoon’s motion and structural integrity.Four different space sizes are set for the pontoon system:5 m,5.5 m,6 m,and 6.5 m.The frequency domain shows that the pontoon space affects the RAO in wave periods ranging from 3 s to 5 s.At wave periods of 3 s,4 s,and 5 s,the pontoon space significantly affects the maximum motion and chain tension parameter values,which are evaluated via time domain simulation.The critical stress of the pontoon is shown at a wave period of 5 s for 5 m and 5.5 m of pontoon space,which shows that the stress can reach 248 MPa.展开更多
The global rise in energy demand, particularly in remote and sparsely populated regions, necessitates innovative and cost-effective electrical distribution solutions. Traditional Rural Electrification (RE) methods, li...The global rise in energy demand, particularly in remote and sparsely populated regions, necessitates innovative and cost-effective electrical distribution solutions. Traditional Rural Electrification (RE) methods, like Conventional Rural Electrification (CRE), have proven economically unfeasible in such areas due to high infrastructure costs and low electricity demand. Consequently, Unconventional Rural Electrification (URE) technologies, such as Capacitor Coupled Substations (CCS), are gaining attention as viable alternatives. This study presents the design and simulation of an 80 kW CCS system, which taps power directly from a 132 kV transmission line to supply low-voltage consumers. The critical components of the CCS, the capacitors are calculated, then a MATLAB/Simulink model with the attained results is executed. Mathematical representation and state-space representation for maintaining the desired tapped voltage area also developed. The research further explores the feasibility and operational performance of this CCS configuration, aiming to address the challenges of rural electrification by offering a sustainable and scalable solution. The results show that the desired value of the tapped voltage can be achieved at any level of High Voltage (HV) with the selection of capacitors that are correctly rated. With an adequately designed control strategy, the research also shows that tapped voltage can be attained under both steady-state and dynamic loads. By leveraging CCS technology, the study demonstrates the potential for delivering reliable electricity to underserved areas, highlighting the system’s practicality and effectiveness in overcoming the limitations of conventional distribution methods.展开更多
The utilization of multi-field coupling simulation methods has become a pivotal approach for the investigation of intricate fracture behavior and interaction mechanisms of rock masses in deep strata.The high temperatu...The utilization of multi-field coupling simulation methods has become a pivotal approach for the investigation of intricate fracture behavior and interaction mechanisms of rock masses in deep strata.The high temperatures,pressures and complex geological environments of deep strata frequently result in the coupling of multiple physical fields,including mechanical,thermal and hydraulic fields,during the fracturing of rocks.This review initially presents an overview of the coupling mechanisms of these physical fields,thereby elucidating the interaction processes ofmechanical,thermal,and hydraulic fields within rockmasses.Secondly,an in-depth analysis ofmulti-field coupling is conducted from both spatial and temporal perspectives,with the introduction of simulation methods for a range of scales.It emphasizes cross-scale coupling methodologies for the transfer of rock properties and physical field data,including homogenization techniques,nested coupling strategies and data-driven approaches.To address the discontinuous characteristics of the rock fracture process,the review provides a detailed explanation of continuousdiscontinuous couplingmethods,to elucidate the evolution of rock fracturing and deformationmore comprehensively.In conclusion,the review presents a summary of the principal points,challenges and future directions of multi-field coupling simulation research.It also puts forward the potential of integrating intelligent algorithms with multi-scale simulation techniques to enhance the accuracy and efficiency of multi-field coupling simulations.This offers novel insights into multi-field coupling simulation analysis in deep rock masses.展开更多
The coupling between heat and pressure is the kernel of inertia friction welding(IFW)and is still not fully understood.A novel 3D fully coupled finite element model based on a plastic friction pair was developed to si...The coupling between heat and pressure is the kernel of inertia friction welding(IFW)and is still not fully understood.A novel 3D fully coupled finite element model based on a plastic friction pair was developed to simulate the IFW process of a Ni-based superalloy and reveal the omnidirectional thermo-mechanical coupling mechanism of the friction interface.The numerical model successfully simulated the deceleration,deformation processes,and peak torsional moments in IFW and captured the evolution of temperature,contact pressure,and stress.The simulated results were validated through measured thermal history,optical macrography,and axial shortening.The results indicated that interfacial friction heat was the primary heat source,and plastic deformation energy only accounted for 4%of the total.The increase in initial rotational speed and friction pressure elevated the peak temperature,reaching a maximum of 1525.5K at an initial rotational speed of 2000 r/min and friction pressure of 400 MPa.The interface heat generation could form an axial temperature gradient exceeding 320K/mm.The radial inhomogeneities of heat generation and temperature were manifested in a concentric ring distribution with maximum heat flux and temperature ranging from 2/5 to 2/3 radius.The radial inhomogeneities were caused by increasing linear velocity along the radius and an opposite distribution of contact pressure,which could reach 1.7 times the set pressure at the center.The circumferential inhomogeneity of thermomechanical distribution during rotary friction welding was revealed for the first time,benefiting from the 3D model.The deflection and transformation of distribution in contact pressure and Mises stress were indicators of plastic deformation and transition of quasi-steady state welding.The critical Mises stress was 0.5 times the friction pressure in this study.The presented modeling provides a reliable insight into the thermo-mechanical coupling mechanism of IFW and lays a solid foundation for predicting the microstructures and mechanical properties of inertia friction welded joints.展开更多
In the context of global warming and intensified human activities,glacier instability in plateau regions has increased,and glacier debris flows have become active,which poses a significant threat to the lives and prop...In the context of global warming and intensified human activities,glacier instability in plateau regions has increased,and glacier debris flows have become active,which poses a significant threat to the lives and property of people and socioeconomic development.The mass movement process of glacier debris flows is extremely complex,so this paper uses the 2018 Sedongpu glacier debris flow event on the Qinghai-Tibet Plateau as an example and applies a numerical simulation method to invert the whole process of mass movement.In view of the interaction between phases in the process of motion,we use the fluid-solid coupling method to describe the mass movement.The granular-flow model and drift-flux model are employed in FLOW3D software to study the mass movement process of glacier debris flows and explore their dynamic characteristics.The results indicate that the glacier debris flow lasted for 700 s,and the movement process was roughly divided into four stages,including initiation,scraping,surging and deposition;the depositional characteristics calculated by the fluid-solid coupling model are consistent with the actual survey results and have good reliability;strong erosion occurs during the mass movement,the clear volume amplification effect,and the first wave climbs 17.8 m across the slope.The fluid-solid coupling method can better simulate glacier debris flows in plateau regions,which is helpful for the study of the mechanism and dynamic characteristics of such disasters.展开更多
Increased human activities in China's coastal zone have resulted in the depletion of ecological land resources.Thus,conducting current and future multi-scenario simulation research on land use and land cover chang...Increased human activities in China's coastal zone have resulted in the depletion of ecological land resources.Thus,conducting current and future multi-scenario simulation research on land use and land cover change(LUCC)is crucial for guiding the healthy and sustainable development of coastal zones.System dynamic(SD)-future land use simulation(FLUS)model,a coupled simulation model,was developed to analyze land use dynamics in China's coastal zone.This model encompasses five scenarios,namely,SSP1-RCP2.6(A),SSP2-RCP4.5(B),SSP3-RCP4.5(C),SSP4-RCP4.5(D),and SSP5-RCP8.5(E).The SD model simulates land use demand on an annual basis up to the year 2100.Subsequently,the FLUS model determines the spatial distribution of land use for the near term(2035),medium term(2050),and long term(2100).Results reveal a slowing trend in land use changes in China's coastal zone from 2000–2020.Among these changes,the expansion rate of construction land was the highest and exhibited an annual decrease.By 2100,land use predictions exhibit high accuracy,and notable differences are observed in trends across scenarios.In summary,the expansion of production,living,and ecological spaces toward the sea remains prominent.Scenario A emphasizes reduced land resource dependence,benefiting ecological land protection.Scenario B witnesses an intensified expansion of artificial wetlands.Scenario C sees substantial land needs for living and production,while Scenario D shows coastal forest and grassland shrinkage.Lastly,in Scenario E,the conflict between humans and land intensifies.This study presents pertinent recommendations for the future development,utilization,and management of coastal areas in China.The research contributes valuable scientific support for informed,long-term strategic decision making within coastal regions.展开更多
The properties of the magnetic mold in magnetic mold casting directly determine the quality of the final cast parts.In this study,the magnetic mold properties in magnetic mold casting,were studied utilizing a coupled ...The properties of the magnetic mold in magnetic mold casting directly determine the quality of the final cast parts.In this study,the magnetic mold properties in magnetic mold casting,were studied utilizing a coupled electromagnetic-structural method through numerical simulation.This study investigated key factors including equivalent stress,the distribution of tensile and compressive stresses,and the area ratio of tensile stress.It compared molds made entirely of magnetic materials with those made partially of magnetic materials.Simulation results indicate that as current increases from 4 A to 8 A,both the initial magnetic mold and the material-replaced magnetic mold initially show an increasing trend in equivalent stress,tensile-compressive stress,and the area ratio of tensile stress,peaking at 6 A before declining.After material replacement,the area ratio of tensile stress at 6 A decreases to 19.84%,representing a reduction of 29.72%.Magnetic molds comprising a combination of magnetic and non-magnetic materials exhibit sufficient strength and a reduced area ratio of tensile stress compared to those made entirely from magnetic materials.This study provides valuable insights for optimizing magnetic mold casting processes and offers practical guidance for advancing the application of magnetic molds.展开更多
The spatiotemporal distribution characteristics of the regression rate are crucial aspects of the research on Hybrid Rocket Motor(HRM). This study presents a pioneering effort in achieving a comprehensive numerical si...The spatiotemporal distribution characteristics of the regression rate are crucial aspects of the research on Hybrid Rocket Motor(HRM). This study presents a pioneering effort in achieving a comprehensive numerical simulation of fluid dynamics and heat transfer in both the fluid and solid regions throughout the entire operation of an HRM. To accomplish this, a dynamic grid technique that incorporates fluid–solid coupling is utilized. To validate the precision of the numerical simulations, a firing test is conducted, with embedded thermocouple probes being used to measure the inner temperature of the fuel grain. The temperature variations in the solid fuel obtained from both experiment and simulations show good agreement. The maximum combustion temperature and average thrust obtained from the simulations are found to deviate from the experimental results by only 3.3% and 2.4%, respectively. Thus, it can be demonstrated that transient numerical simulations accurately capture the fluid–solid coupling characteristics and transient regression rate. The dynamic simulation results of inner flow field and solid region throughout the entire working stage reveal that the presence of vortices enhances the blending of combustion gases and improves the regression rate at both the front and rear ends of the fuel grain. In addition, oscillations of the regression rate obtained in the simulation can also be well corresponded with the corrugated surface observed in the experiment. Furthermore, the zero-dimension regression rate formula and the formula describing the axial location dependence of the regression rate are fitted from the simulation results, with the corresponding coefficients of determination(R^(2)) of 0.9765 and 0.9298, respectively.This research serves as a reference for predicting the performance of HRM with gas oxygen and polyethylene, and presents a credible way for investigating the spatiotemporal distribution of the regression rate.展开更多
The atmospheric carbon dioxide(CO_(2))concentration has been increasing rapidly since the Industrial Revolution,which has led to unequivocal global warming and crucial environmental change.It is extremely important to...The atmospheric carbon dioxide(CO_(2))concentration has been increasing rapidly since the Industrial Revolution,which has led to unequivocal global warming and crucial environmental change.It is extremely important to investigate the interactions among atmospheric CO_(2),the physical climate system,and the carbon cycle of the underlying surface for a better understanding of the Earth system.Earth system models are widely used to investigate these interactions via coupled carbon-climate simulations.The Chinese Academy of Sciences Earth System Model version 2(CAS-ESM2.0)has successfully fixed a two-way coupling of atmospheric CO_(2)with the climate and carbon cycle on land and in the ocean.Using CAS-ESM2.0,we conducted a coupled carbon-climate simulation by following the CMIP6 proposal of a historical emissions-driven experiment.This paper examines the modeled CO_(2)by comparison with observed CO_(2)at the sites of Mauna Loa and Barrow,and the Greenhouse Gases Observing Satellite(GOSAT)CO_(2)product.The results showed that CAS-ESM2.0 agrees very well with observations in reproducing the increasing trend of annual CO_(2)during the period 1850-2014,and in capturing the seasonal cycle of CO_(2)at the two baseline sites,as well as over northern high latitudes.These agreements illustrate a good ability of CAS-ESM2.0 in simulating carbon-climate interactions,even though uncertainties remain in the processes involved.This paper reports an important stage of the development of CAS-ESM with the coupling of carbon and climate,which will provide significant scientific support for climate research and China’s goal of carbon neutrality.展开更多
Magnetohydrodynamic(MHD)induction pumps are contactless pumps able to withstand harsh environments.The rate of fluid flow through the pump directly affects the efficiency and stability of the device.To explore the inf...Magnetohydrodynamic(MHD)induction pumps are contactless pumps able to withstand harsh environments.The rate of fluid flow through the pump directly affects the efficiency and stability of the device.To explore the influence of induction pump settings on the related delivery speed,in this study,a numerical model for coupled electromagnetic and flow field effects is introduced and used to simulate liquid metal lithium flow in the induction pump.The effects of current intensity,frequency,coil turns and coil winding size on the velocity of the working fluid are analyzed.It is shown that the first three parameters have a significant impact,while changes in the coil turns have a negligible influence.The maximum increase in working fluid velocity within the pump for the parameter combination investigated in this paper is approximately 618%.As the frequency is increased from 20 to 60 Hz,the maximum increase in the mean flow rate of the working fluid is approximately 241%.These research findings are intended to support the design and optimization of these devices.展开更多
To predict three-dimensional temperature distribution of molten aluminum and its influencing factors inside an industrial aluminum holding furnace,a fluid-solid coupled method was presented.The fluid-solid coupled mat...To predict three-dimensional temperature distribution of molten aluminum and its influencing factors inside an industrial aluminum holding furnace,a fluid-solid coupled method was presented.The fluid-solid coupled mathematics models of aluminum holding furnace in the premixed combustion processing were established based on mass conservation,moment conservation,momentum conservation,energy conservation and chemistry species conservation.Computational results agree well with the test data of the typical condition.The maximum combustion temperature is 1 850 K.The average temperature of the molten aluminum is 1 158 K,and the maximum temperature difference is about 240 K.The average temperature increases 0.3 ℃ while the temperature of combustion air increases 1 ℃.The optimal excess air ratio is 1.25-1.30.展开更多
A mathematical model, fully coupling multiple porous media deformation and fluid flow, was established based on the elastic theory of porous media and fluid-solid coupling mechanism in tight oil reservoirs. The finite...A mathematical model, fully coupling multiple porous media deformation and fluid flow, was established based on the elastic theory of porous media and fluid-solid coupling mechanism in tight oil reservoirs. The finite element method was used to determine the numerical solution and the accuracy of the model was verified. On this basis, the model was used to simulate productivity of multistage fractured horizontal wells in tight oil reservoirs. The results show that during the production of tight oil wells, the reservoir region close to artificial fractures deteriorated in physical properties significantly, e.g. the aperture and conductivity of artificial fractures dropped by 52.12% and 89.02% respectively. The simulations of 3000-day production of a horizontal well in tight oil reservoir showed that the predicted productivity by the uncoupled model had an error of 38.30% from that by the fully-coupled model. Apparently, ignoring the influence of fluid-solid interaction effect led to serious deviations of the productivity prediction results. The productivity of horizontal well in tight oil reservoir was most sensitive to the start-up pressure gradient, and second most sensitive to the opening of artificial fractures. Enhancing the initial conductivity of artificial fractures was helpful to improve the productivity of tight oil wells. The influence of conductivity, spacing, number and length of artificial fractures should be considered comprehensively in fracturing design. Increasing the number of artificial fractures unilaterally could not achieve the expected increase in production.展开更多
In order to quantitively model the real solidification process of industrial multicomponent alloys, a non-isothermal phase field model was studied for multicomponent alloy fully coupled with thermodynamic and diffusio...In order to quantitively model the real solidification process of industrial multicomponent alloys, a non-isothermal phase field model was studied for multicomponent alloy fully coupled with thermodynamic and diffusion mobility database, which can accurately predict the phase equilibrium, solute diffusion coefficients, specific heat capacity and latent heat release in the whole system. The results show that these parameters are not constants and their values depend on local concentration and temperature. Quantitative simulation of solidification in multicomponent alloys is almost impossible without such parameters available. In this model, the interfacial region is assumed to be a mixture of solid and liquid with the same chemical potentials, but with different composition. The anti-trapping current is also considered in the model. And this model was successfully applied to industrial A1-Cu-Mg alloy for the free equiaxed dendrite solidification process.展开更多
Deep tight reservoirs exhibit complex stress and seepage fields due to varying pore structures,thus the seepage characteristics are significant for enhancing oil production.This study conducted triaxial compression an...Deep tight reservoirs exhibit complex stress and seepage fields due to varying pore structures,thus the seepage characteristics are significant for enhancing oil production.This study conducted triaxial compression and permeability tests to investigate the mechanical and seepage properties of tight sandstone.A digital core of tight sandstone was built using Computed Tomography(CT)scanning,which was divided into matrix and pore phases by a pore equivalent diameter threshold.A fluid-solid coupling model was established to investigate the seepage characteristics at micro-scale.The results showed that increasing the confining pressure decreased porosity,permeability,and flow velocity,with the pore phase becoming the dominant seepage channel.Cracks and large pores closed first under increasing pressure,resulted in a steep drop in permeability.However,permeability slightly decreased under high confining pressure,which followed a first-order exponential function.Flow velocity increased with seepage pressure.And the damage mainly occurred in stress-concentration regions under low seepage pressure.Seepage behavior followed linear Darcy flow,the damage emerged at seepage entrances under high pressure,which decreased rock elastic modulus and significantly increased permeability.展开更多
During the propagation of high-power lasers within internal channels,the laser beam heats the propagation medium,causing the thermal blooming effect that degrades the beam quality at the output.The intricate configura...During the propagation of high-power lasers within internal channels,the laser beam heats the propagation medium,causing the thermal blooming effect that degrades the beam quality at the output.The intricate configuration of the optical path within the internal channel necessitates complex and time-consuming efforts to assess the impact of thermal blooming effect on the optical path.To meet the engineering need for rapid evaluation of thermal blooming effect in optical paths,this study proposed a rapid simulation method for the thermal blooming effect in internal optical paths based on the finite element method.This method discretized the fluid region into infinitesimal elements and employed finite element method for flow field analysis.A simplified analytical model of the flow field region in complex internal channels was established,and regions with similar thermal blooming effect were divided within this model.Based on the calculated optical path differences within these regions,numerical simulations of phase distortion caused by thermal blooming were conducted.The calculated result were compared with those obtained using the existing methods.The findings reveal that for complex optical paths,the discrepancy between the two approaches is less than 3.6%,with similar phase distortion patterns observed.For L-type units,this method and the existing methods identify the same primary factors influencing aberrations and exhibit consistent trends in their variation.This method was used to analyze the impact of thermal blooming effect in a straight channel under different gravity directions.The results show that phase distortion varies with changes in the direction of gravity,and the magnitude of the phase difference is strongly correlated with the component of gravity perpendicular to the optical axis.Compared to the existing methods,this approach offers greater flexibility,obviates the need for complex custom analysis programming.The analytical results of this method enable a rapid assessment of the thermal blooming effect in optical paths within the internal channel.This is especially useful during the engineering design.These results also provide crucial references for developing strategies to suppress thermal blooming effect.展开更多
Deep underground excavation causes considerable unloading effects,leading to a pronounced bias pressure phenomenon.The deformation and seepage characteristics of rock masses under different gas and confining pressures...Deep underground excavation causes considerable unloading effects,leading to a pronounced bias pressure phenomenon.The deformation and seepage characteristics of rock masses under different gas and confining pressures were investigated via triaxial loading and unloading seepage tests.When the influential coefficient of effective confining pressure(β)is less than 0.065,the seepage force considerably weakens the strength of fractured rock masses.Conversely,whenβis greater than 0.065,the opposite is true.Moreover,the increase in the axial load leads to an increase in the precast fracture volumetric strain,which is the main reason for the increase in fracture permeability.This effect is particularly significant during the unloading stage.Based on the test results,a method for calculating the dynamic seepage evolution of rock masses,considering the effects of rock mass damage and fracture deformation,is introduced,and the effectiveness of the calculation is validated.The entire description of the seepage under loading and unloading was accomplished.The equivalent relationship between the lateral and normal stresses on fracture surfaces ranges from 0.001 to 0.1,showing an exponential variation between the lateral stress influence coefficient on normal deformation(χ)and seepage pressure.Before the failure of the rock mass,the seepage in the fractures was in a linear laminar flow state.However,after the failure,when the gas pressure reached 2 MPa,the flow state in the fractures transitioned to nonlinear laminar flow.The results are important for predicting hazardous gas leaks during deep underground engineering excavation.展开更多
Hydraulic fracturing technology has played an important role in the exploitation of unconventional oil and gas resources,however,its application to gas hydrate reservoirs has been rarely studied.Currently,there is sti...Hydraulic fracturing technology has played an important role in the exploitation of unconventional oil and gas resources,however,its application to gas hydrate reservoirs has been rarely studied.Currently,there is still limited understanding of the propagation and extension of fractures around the wellbore during the fracturing process of horizontal wells in hydrate reservoirs,as well as the stress interference patterns between fractures.This study simulates hydraulic fracturing processes in hydrate reservoirs using a fluidsolid coupling discrete element method(DEM),and analyzes the impacts of hydrate saturation and geological and engineering factors on fracture extension and stress disturbance.The results show that hydraulic fracturing is more effective when hydrate saturation exceeds 30%and that fracture pressure increases with saturation.The increase in horizontal stress differential enhances the directionality of fracture propagation and reduces stress disturbance.The distribution uniformity index(DUI)reveals that injection pressure is directly proportional to the number of main fractures and inversely proportional to fracturing time,with fracturing efficiency depending on the spacing between injection points and the distance between wells.This work may provide reference for the commercial exploitation of natural gas hydrates.展开更多
As energy demand increases,the depth of mining is increasing,and methane disasters grow more serious,efficient extraction of methane is the ultimate method of preventing and controlling methane disasters.The objective...As energy demand increases,the depth of mining is increasing,and methane disasters grow more serious,efficient extraction of methane is the ultimate method of preventing and controlling methane disasters.The objectives for this research are to explore the efficiency of N_(2) injection to enhance gas extraction from coal seams(N_(2)-ECGE)and its impact on coal seam permeability.By developing a fluid-solid coupling model and using COMSOL Multiphysics to perform numerical simulations,the changes in gas pressure,methane content,gas production,output rate and permeability of coal seams were comparatively analyzed under the two methods of direct extraction and N_(2)-ECGE.The research results show that N_(2)-ECGE can significantly improve the coal seam gas pressure and reduce the coal seam CH_(4) content,and the larger the N_(2) injection pressure the more significant the reduction effect.Meanwhile,N_(2)-ECGE can significantly increase the CH_(4) extraction and output rate,and the increase of N_(2) pressure further improves the extraction efficiency.In addition,the pressure of nitrogen injection has a remarkable effect on coal seam permeability,high pressure of nitrogen injection can increase the permeability in the time of no disturbance,but the rate of permeability decreases more quickly after disturbed.The effect of strain due to adsorption desorption on coal seam permeability dominates.Despite model construction limitations,this research offers essential theoretical and practical direction for N_(2) injection to enhance the permeability evolution law of coal seam gas extraction process.展开更多
The integrated system composed of wave energy converters and floating wind turbines offers substantial potential for reducing the levelized cost of energy(LCOE) by sharing the infrastructure, mooring system, substatio...The integrated system composed of wave energy converters and floating wind turbines offers substantial potential for reducing the levelized cost of energy(LCOE) by sharing the infrastructure, mooring system, substations and cables.This paper proposes an integrated system consisting of a semi-submersible wind turbine platform and three Wave Star flap-type wave energy converters. The coupled motion model of the integrated system is established and validated on the basis of viscously corrected potential flow theory. This study investigates the influence of two key parameters,the arm length and hinge points of flap-type wave energy converters, on system performance. The results reveal that variations in the arm length of flap-type wave energy converters(WECs) are the primary determinants of the integrated system's dynamic characteristics, whereas changes in hinge points predominantly affect device power generation.Additionally, incorporating WECs reduces the pitch and heave motions of the platform within a specific wave frequency range, thereby enhancing the energy output of the integrated system at the operational sea site. The performance of this hybrid system at a selected sea site is further assessed via the proposed aero-hydroservo coupling simulations.展开更多
In this paper,a high-fidelity computational fluid dynamics(CFD)and rigid body dynamics(RBD)coupled platform for virtual flight simulation is developed to investigate the flight stability of fixed canard dual-spin proj...In this paper,a high-fidelity computational fluid dynamics(CFD)and rigid body dynamics(RBD)coupled platform for virtual flight simulation is developed to investigate the flight stability of fixed canard dual-spin projectile.The platform's reliability is validated by reproducing the characteristic resonance instability of such projectiles.By coupling the solution of the Unsteady Reynolds-Averaged Navier-Stokes equations and the seven-degree-of-freedom RBD equations,the virtual flight simulations of fixed canard dual-spin projectiles at various curvature trajectories are achieved,and the dynamic mechanism of the trajectory following process is analyzed.The instability mechanism of the dynamic instability during trajectory following process of the fixed canard dual-spin projectile is elucidated by simulating the rolling/coning coupled forced motion,and subsequently validated through virtual flight simulations.The findings suggest that an appropriate yaw moment can drive the projectile axis to precession in the tangential direction of the trajectory,thereby enhancing the trajectory following stability.However,the damping of the projectile attains its minimum value when the forward body equilibrium rotational speed(-128 rad/s)is equal to the negative of the fast mode frequency of the projectile.Insufficient damping leads to the fixed canard dual-spin projectile exiting the dynamic stability domain during the trajectory following,resulting in weakly damped instability.Keeping the forward body not rotating or increasing the spin rates to-192 rad/s can enhance the projectile's damping,thereby improving its dynamic stability.展开更多
基金financially supported by the Riset Pengembangan dan Penerapan(RPP),Diponegoro University 2023 research scheme with contract number 609-18/UN7.D2/PP/VIII/2023.
文摘Shallow water infrastructure needs to support increased activity on the shores of Semarang.This study chooses several pontoons because of their good stability,rolling motion,and more expansive space.A coupled simulation method consisting of hydrodynamic and structural calculations has been used to evaluate a catamaran pontoon’s motion and structural integrity.Four different space sizes are set for the pontoon system:5 m,5.5 m,6 m,and 6.5 m.The frequency domain shows that the pontoon space affects the RAO in wave periods ranging from 3 s to 5 s.At wave periods of 3 s,4 s,and 5 s,the pontoon space significantly affects the maximum motion and chain tension parameter values,which are evaluated via time domain simulation.The critical stress of the pontoon is shown at a wave period of 5 s for 5 m and 5.5 m of pontoon space,which shows that the stress can reach 248 MPa.
文摘The global rise in energy demand, particularly in remote and sparsely populated regions, necessitates innovative and cost-effective electrical distribution solutions. Traditional Rural Electrification (RE) methods, like Conventional Rural Electrification (CRE), have proven economically unfeasible in such areas due to high infrastructure costs and low electricity demand. Consequently, Unconventional Rural Electrification (URE) technologies, such as Capacitor Coupled Substations (CCS), are gaining attention as viable alternatives. This study presents the design and simulation of an 80 kW CCS system, which taps power directly from a 132 kV transmission line to supply low-voltage consumers. The critical components of the CCS, the capacitors are calculated, then a MATLAB/Simulink model with the attained results is executed. Mathematical representation and state-space representation for maintaining the desired tapped voltage area also developed. The research further explores the feasibility and operational performance of this CCS configuration, aiming to address the challenges of rural electrification by offering a sustainable and scalable solution. The results show that the desired value of the tapped voltage can be achieved at any level of High Voltage (HV) with the selection of capacitors that are correctly rated. With an adequately designed control strategy, the research also shows that tapped voltage can be attained under both steady-state and dynamic loads. By leveraging CCS technology, the study demonstrates the potential for delivering reliable electricity to underserved areas, highlighting the system’s practicality and effectiveness in overcoming the limitations of conventional distribution methods.
基金supported by the National Natural Science Foundation of China(Grant Nos.42477185,41602308)the Zhejiang Provincial Natural Science Foundation of China(Grant No.LY20E080005)the Postgraduate Course Construction Project of Zhejiang University of Science and Technology(Grant No.2021yjskj05).
文摘The utilization of multi-field coupling simulation methods has become a pivotal approach for the investigation of intricate fracture behavior and interaction mechanisms of rock masses in deep strata.The high temperatures,pressures and complex geological environments of deep strata frequently result in the coupling of multiple physical fields,including mechanical,thermal and hydraulic fields,during the fracturing of rocks.This review initially presents an overview of the coupling mechanisms of these physical fields,thereby elucidating the interaction processes ofmechanical,thermal,and hydraulic fields within rockmasses.Secondly,an in-depth analysis ofmulti-field coupling is conducted from both spatial and temporal perspectives,with the introduction of simulation methods for a range of scales.It emphasizes cross-scale coupling methodologies for the transfer of rock properties and physical field data,including homogenization techniques,nested coupling strategies and data-driven approaches.To address the discontinuous characteristics of the rock fracture process,the review provides a detailed explanation of continuousdiscontinuous couplingmethods,to elucidate the evolution of rock fracturing and deformationmore comprehensively.In conclusion,the review presents a summary of the principal points,challenges and future directions of multi-field coupling simulation research.It also puts forward the potential of integrating intelligent algorithms with multi-scale simulation techniques to enhance the accuracy and efficiency of multi-field coupling simulations.This offers novel insights into multi-field coupling simulation analysis in deep rock masses.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFB3404904)。
文摘The coupling between heat and pressure is the kernel of inertia friction welding(IFW)and is still not fully understood.A novel 3D fully coupled finite element model based on a plastic friction pair was developed to simulate the IFW process of a Ni-based superalloy and reveal the omnidirectional thermo-mechanical coupling mechanism of the friction interface.The numerical model successfully simulated the deceleration,deformation processes,and peak torsional moments in IFW and captured the evolution of temperature,contact pressure,and stress.The simulated results were validated through measured thermal history,optical macrography,and axial shortening.The results indicated that interfacial friction heat was the primary heat source,and plastic deformation energy only accounted for 4%of the total.The increase in initial rotational speed and friction pressure elevated the peak temperature,reaching a maximum of 1525.5K at an initial rotational speed of 2000 r/min and friction pressure of 400 MPa.The interface heat generation could form an axial temperature gradient exceeding 320K/mm.The radial inhomogeneities of heat generation and temperature were manifested in a concentric ring distribution with maximum heat flux and temperature ranging from 2/5 to 2/3 radius.The radial inhomogeneities were caused by increasing linear velocity along the radius and an opposite distribution of contact pressure,which could reach 1.7 times the set pressure at the center.The circumferential inhomogeneity of thermomechanical distribution during rotary friction welding was revealed for the first time,benefiting from the 3D model.The deflection and transformation of distribution in contact pressure and Mises stress were indicators of plastic deformation and transition of quasi-steady state welding.The critical Mises stress was 0.5 times the friction pressure in this study.The presented modeling provides a reliable insight into the thermo-mechanical coupling mechanism of IFW and lays a solid foundation for predicting the microstructures and mechanical properties of inertia friction welded joints.
基金supported by the National Natural Science Foundation of China(Nos.U20A20111,41977229)the Sichuan Youth Science and Technology Innovation Research Team Project(No.2020JDTD0006).
文摘In the context of global warming and intensified human activities,glacier instability in plateau regions has increased,and glacier debris flows have become active,which poses a significant threat to the lives and property of people and socioeconomic development.The mass movement process of glacier debris flows is extremely complex,so this paper uses the 2018 Sedongpu glacier debris flow event on the Qinghai-Tibet Plateau as an example and applies a numerical simulation method to invert the whole process of mass movement.In view of the interaction between phases in the process of motion,we use the fluid-solid coupling method to describe the mass movement.The granular-flow model and drift-flux model are employed in FLOW3D software to study the mass movement process of glacier debris flows and explore their dynamic characteristics.The results indicate that the glacier debris flow lasted for 700 s,and the movement process was roughly divided into four stages,including initiation,scraping,surging and deposition;the depositional characteristics calculated by the fluid-solid coupling model are consistent with the actual survey results and have good reliability;strong erosion occurs during the mass movement,the clear volume amplification effect,and the first wave climbs 17.8 m across the slope.The fluid-solid coupling method can better simulate glacier debris flows in plateau regions,which is helpful for the study of the mechanism and dynamic characteristics of such disasters.
基金Under the auspices of National Natural Science Foundation of China (No.42176221,41901133)Strategic Priority Research Program of the Chinese Academy of Sciences (No.XDA19060205)Seed project of Yantai Institute of Coastal Zone Research,Chinese Academy of Sciences (No.YIC-E3518907)。
文摘Increased human activities in China's coastal zone have resulted in the depletion of ecological land resources.Thus,conducting current and future multi-scenario simulation research on land use and land cover change(LUCC)is crucial for guiding the healthy and sustainable development of coastal zones.System dynamic(SD)-future land use simulation(FLUS)model,a coupled simulation model,was developed to analyze land use dynamics in China's coastal zone.This model encompasses five scenarios,namely,SSP1-RCP2.6(A),SSP2-RCP4.5(B),SSP3-RCP4.5(C),SSP4-RCP4.5(D),and SSP5-RCP8.5(E).The SD model simulates land use demand on an annual basis up to the year 2100.Subsequently,the FLUS model determines the spatial distribution of land use for the near term(2035),medium term(2050),and long term(2100).Results reveal a slowing trend in land use changes in China's coastal zone from 2000–2020.Among these changes,the expansion rate of construction land was the highest and exhibited an annual decrease.By 2100,land use predictions exhibit high accuracy,and notable differences are observed in trends across scenarios.In summary,the expansion of production,living,and ecological spaces toward the sea remains prominent.Scenario A emphasizes reduced land resource dependence,benefiting ecological land protection.Scenario B witnesses an intensified expansion of artificial wetlands.Scenario C sees substantial land needs for living and production,while Scenario D shows coastal forest and grassland shrinkage.Lastly,in Scenario E,the conflict between humans and land intensifies.This study presents pertinent recommendations for the future development,utilization,and management of coastal areas in China.The research contributes valuable scientific support for informed,long-term strategic decision making within coastal regions.
基金the National Natural Science Foundation of China(No.51875062,No.52205336)the China Postdoctoral Science Foundation(No.2021M700567).
文摘The properties of the magnetic mold in magnetic mold casting directly determine the quality of the final cast parts.In this study,the magnetic mold properties in magnetic mold casting,were studied utilizing a coupled electromagnetic-structural method through numerical simulation.This study investigated key factors including equivalent stress,the distribution of tensile and compressive stresses,and the area ratio of tensile stress.It compared molds made entirely of magnetic materials with those made partially of magnetic materials.Simulation results indicate that as current increases from 4 A to 8 A,both the initial magnetic mold and the material-replaced magnetic mold initially show an increasing trend in equivalent stress,tensile-compressive stress,and the area ratio of tensile stress,peaking at 6 A before declining.After material replacement,the area ratio of tensile stress at 6 A decreases to 19.84%,representing a reduction of 29.72%.Magnetic molds comprising a combination of magnetic and non-magnetic materials exhibit sufficient strength and a reduced area ratio of tensile stress compared to those made entirely from magnetic materials.This study provides valuable insights for optimizing magnetic mold casting processes and offers practical guidance for advancing the application of magnetic molds.
基金supported by the National Natural Science Foundation of China (No.U20B2034).
文摘The spatiotemporal distribution characteristics of the regression rate are crucial aspects of the research on Hybrid Rocket Motor(HRM). This study presents a pioneering effort in achieving a comprehensive numerical simulation of fluid dynamics and heat transfer in both the fluid and solid regions throughout the entire operation of an HRM. To accomplish this, a dynamic grid technique that incorporates fluid–solid coupling is utilized. To validate the precision of the numerical simulations, a firing test is conducted, with embedded thermocouple probes being used to measure the inner temperature of the fuel grain. The temperature variations in the solid fuel obtained from both experiment and simulations show good agreement. The maximum combustion temperature and average thrust obtained from the simulations are found to deviate from the experimental results by only 3.3% and 2.4%, respectively. Thus, it can be demonstrated that transient numerical simulations accurately capture the fluid–solid coupling characteristics and transient regression rate. The dynamic simulation results of inner flow field and solid region throughout the entire working stage reveal that the presence of vortices enhances the blending of combustion gases and improves the regression rate at both the front and rear ends of the fuel grain. In addition, oscillations of the regression rate obtained in the simulation can also be well corresponded with the corrugated surface observed in the experiment. Furthermore, the zero-dimension regression rate formula and the formula describing the axial location dependence of the regression rate are fitted from the simulation results, with the corresponding coefficients of determination(R^(2)) of 0.9765 and 0.9298, respectively.This research serves as a reference for predicting the performance of HRM with gas oxygen and polyethylene, and presents a credible way for investigating the spatiotemporal distribution of the regression rate.
基金the National Key Research and Development Program of China(Grant No.2022YFE0106500)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.2022076)+1 种基金the National Key Scientific and Technological Infrastructure project“Earth System Numerical Simulation Facility”(EarthLab2023-EL-ZD-00012)。
文摘The atmospheric carbon dioxide(CO_(2))concentration has been increasing rapidly since the Industrial Revolution,which has led to unequivocal global warming and crucial environmental change.It is extremely important to investigate the interactions among atmospheric CO_(2),the physical climate system,and the carbon cycle of the underlying surface for a better understanding of the Earth system.Earth system models are widely used to investigate these interactions via coupled carbon-climate simulations.The Chinese Academy of Sciences Earth System Model version 2(CAS-ESM2.0)has successfully fixed a two-way coupling of atmospheric CO_(2)with the climate and carbon cycle on land and in the ocean.Using CAS-ESM2.0,we conducted a coupled carbon-climate simulation by following the CMIP6 proposal of a historical emissions-driven experiment.This paper examines the modeled CO_(2)by comparison with observed CO_(2)at the sites of Mauna Loa and Barrow,and the Greenhouse Gases Observing Satellite(GOSAT)CO_(2)product.The results showed that CAS-ESM2.0 agrees very well with observations in reproducing the increasing trend of annual CO_(2)during the period 1850-2014,and in capturing the seasonal cycle of CO_(2)at the two baseline sites,as well as over northern high latitudes.These agreements illustrate a good ability of CAS-ESM2.0 in simulating carbon-climate interactions,even though uncertainties remain in the processes involved.This paper reports an important stage of the development of CAS-ESM with the coupling of carbon and climate,which will provide significant scientific support for climate research and China’s goal of carbon neutrality.
文摘Magnetohydrodynamic(MHD)induction pumps are contactless pumps able to withstand harsh environments.The rate of fluid flow through the pump directly affects the efficiency and stability of the device.To explore the influence of induction pump settings on the related delivery speed,in this study,a numerical model for coupled electromagnetic and flow field effects is introduced and used to simulate liquid metal lithium flow in the induction pump.The effects of current intensity,frequency,coil turns and coil winding size on the velocity of the working fluid are analyzed.It is shown that the first three parameters have a significant impact,while changes in the coil turns have a negligible influence.The maximum increase in working fluid velocity within the pump for the parameter combination investigated in this paper is approximately 618%.As the frequency is increased from 20 to 60 Hz,the maximum increase in the mean flow rate of the working fluid is approximately 241%.These research findings are intended to support the design and optimization of these devices.
基金Project(2006AA03Z523) supported by the National High-Tech Research and Development Program of ChinaProject(08C26224302178) supported by the Innovation Foundation of Central South University,China
文摘To predict three-dimensional temperature distribution of molten aluminum and its influencing factors inside an industrial aluminum holding furnace,a fluid-solid coupled method was presented.The fluid-solid coupled mathematics models of aluminum holding furnace in the premixed combustion processing were established based on mass conservation,moment conservation,momentum conservation,energy conservation and chemistry species conservation.Computational results agree well with the test data of the typical condition.The maximum combustion temperature is 1 850 K.The average temperature of the molten aluminum is 1 158 K,and the maximum temperature difference is about 240 K.The average temperature increases 0.3 ℃ while the temperature of combustion air increases 1 ℃.The optimal excess air ratio is 1.25-1.30.
基金Supported by the National Science and Technology Major Project (2017ZX05013-005)。
文摘A mathematical model, fully coupling multiple porous media deformation and fluid flow, was established based on the elastic theory of porous media and fluid-solid coupling mechanism in tight oil reservoirs. The finite element method was used to determine the numerical solution and the accuracy of the model was verified. On this basis, the model was used to simulate productivity of multistage fractured horizontal wells in tight oil reservoirs. The results show that during the production of tight oil wells, the reservoir region close to artificial fractures deteriorated in physical properties significantly, e.g. the aperture and conductivity of artificial fractures dropped by 52.12% and 89.02% respectively. The simulations of 3000-day production of a horizontal well in tight oil reservoir showed that the predicted productivity by the uncoupled model had an error of 38.30% from that by the fully-coupled model. Apparently, ignoring the influence of fluid-solid interaction effect led to serious deviations of the productivity prediction results. The productivity of horizontal well in tight oil reservoir was most sensitive to the start-up pressure gradient, and second most sensitive to the opening of artificial fractures. Enhancing the initial conductivity of artificial fractures was helpful to improve the productivity of tight oil wells. The influence of conductivity, spacing, number and length of artificial fractures should be considered comprehensively in fracturing design. Increasing the number of artificial fractures unilaterally could not achieve the expected increase in production.
基金Project(2011CB606306) supported by the National Basic Research Program of ChinaProject(51101014) supported by the National Natural Science Foundation of China
文摘In order to quantitively model the real solidification process of industrial multicomponent alloys, a non-isothermal phase field model was studied for multicomponent alloy fully coupled with thermodynamic and diffusion mobility database, which can accurately predict the phase equilibrium, solute diffusion coefficients, specific heat capacity and latent heat release in the whole system. The results show that these parameters are not constants and their values depend on local concentration and temperature. Quantitative simulation of solidification in multicomponent alloys is almost impossible without such parameters available. In this model, the interfacial region is assumed to be a mixture of solid and liquid with the same chemical potentials, but with different composition. The anti-trapping current is also considered in the model. And this model was successfully applied to industrial A1-Cu-Mg alloy for the free equiaxed dendrite solidification process.
基金financially supported by the National Natural Science Foundation of China(Nos.42272153 and 42472195)the Research Fund of PetroChina Tarim Oilfield Company(No.671023060003)the Research Fund of China National Petroleum Corporation Limited(No.2023ZZ16YJ04).
文摘Deep tight reservoirs exhibit complex stress and seepage fields due to varying pore structures,thus the seepage characteristics are significant for enhancing oil production.This study conducted triaxial compression and permeability tests to investigate the mechanical and seepage properties of tight sandstone.A digital core of tight sandstone was built using Computed Tomography(CT)scanning,which was divided into matrix and pore phases by a pore equivalent diameter threshold.A fluid-solid coupling model was established to investigate the seepage characteristics at micro-scale.The results showed that increasing the confining pressure decreased porosity,permeability,and flow velocity,with the pore phase becoming the dominant seepage channel.Cracks and large pores closed first under increasing pressure,resulted in a steep drop in permeability.However,permeability slightly decreased under high confining pressure,which followed a first-order exponential function.Flow velocity increased with seepage pressure.And the damage mainly occurred in stress-concentration regions under low seepage pressure.Seepage behavior followed linear Darcy flow,the damage emerged at seepage entrances under high pressure,which decreased rock elastic modulus and significantly increased permeability.
文摘During the propagation of high-power lasers within internal channels,the laser beam heats the propagation medium,causing the thermal blooming effect that degrades the beam quality at the output.The intricate configuration of the optical path within the internal channel necessitates complex and time-consuming efforts to assess the impact of thermal blooming effect on the optical path.To meet the engineering need for rapid evaluation of thermal blooming effect in optical paths,this study proposed a rapid simulation method for the thermal blooming effect in internal optical paths based on the finite element method.This method discretized the fluid region into infinitesimal elements and employed finite element method for flow field analysis.A simplified analytical model of the flow field region in complex internal channels was established,and regions with similar thermal blooming effect were divided within this model.Based on the calculated optical path differences within these regions,numerical simulations of phase distortion caused by thermal blooming were conducted.The calculated result were compared with those obtained using the existing methods.The findings reveal that for complex optical paths,the discrepancy between the two approaches is less than 3.6%,with similar phase distortion patterns observed.For L-type units,this method and the existing methods identify the same primary factors influencing aberrations and exhibit consistent trends in their variation.This method was used to analyze the impact of thermal blooming effect in a straight channel under different gravity directions.The results show that phase distortion varies with changes in the direction of gravity,and the magnitude of the phase difference is strongly correlated with the component of gravity perpendicular to the optical axis.Compared to the existing methods,this approach offers greater flexibility,obviates the need for complex custom analysis programming.The analytical results of this method enable a rapid assessment of the thermal blooming effect in optical paths within the internal channel.This is especially useful during the engineering design.These results also provide crucial references for developing strategies to suppress thermal blooming effect.
基金supported by the National Natural Science Foundation of China(Grant No.52374079)Chongqing Graduate Research Innovation Project(Grant No.CYB22032)Chongqing Talents and Outstanding Scientists Project(Grant No.cstc2024ycjhbgzxm0032).
文摘Deep underground excavation causes considerable unloading effects,leading to a pronounced bias pressure phenomenon.The deformation and seepage characteristics of rock masses under different gas and confining pressures were investigated via triaxial loading and unloading seepage tests.When the influential coefficient of effective confining pressure(β)is less than 0.065,the seepage force considerably weakens the strength of fractured rock masses.Conversely,whenβis greater than 0.065,the opposite is true.Moreover,the increase in the axial load leads to an increase in the precast fracture volumetric strain,which is the main reason for the increase in fracture permeability.This effect is particularly significant during the unloading stage.Based on the test results,a method for calculating the dynamic seepage evolution of rock masses,considering the effects of rock mass damage and fracture deformation,is introduced,and the effectiveness of the calculation is validated.The entire description of the seepage under loading and unloading was accomplished.The equivalent relationship between the lateral and normal stresses on fracture surfaces ranges from 0.001 to 0.1,showing an exponential variation between the lateral stress influence coefficient on normal deformation(χ)and seepage pressure.Before the failure of the rock mass,the seepage in the fractures was in a linear laminar flow state.However,after the failure,when the gas pressure reached 2 MPa,the flow state in the fractures transitioned to nonlinear laminar flow.The results are important for predicting hazardous gas leaks during deep underground engineering excavation.
基金financially supported by the National Key Research and Development Plan(2023YFC2811001)the National Natural Science Foundation of China(42206233)the Taishan Scholars Program(tsqn202312280,tsqn202306297)。
文摘Hydraulic fracturing technology has played an important role in the exploitation of unconventional oil and gas resources,however,its application to gas hydrate reservoirs has been rarely studied.Currently,there is still limited understanding of the propagation and extension of fractures around the wellbore during the fracturing process of horizontal wells in hydrate reservoirs,as well as the stress interference patterns between fractures.This study simulates hydraulic fracturing processes in hydrate reservoirs using a fluidsolid coupling discrete element method(DEM),and analyzes the impacts of hydrate saturation and geological and engineering factors on fracture extension and stress disturbance.The results show that hydraulic fracturing is more effective when hydrate saturation exceeds 30%and that fracture pressure increases with saturation.The increase in horizontal stress differential enhances the directionality of fracture propagation and reduces stress disturbance.The distribution uniformity index(DUI)reveals that injection pressure is directly proportional to the number of main fractures and inversely proportional to fracturing time,with fracturing efficiency depending on the spacing between injection points and the distance between wells.This work may provide reference for the commercial exploitation of natural gas hydrates.
基金supported by the National Natural Science Foundation of China(52374249,52130409,52121003)the National Key R&D Program(2023YFC3009003)+1 种基金the Basic Research Business Fees for Central Universities(2024JCCXAQ01)Open Fund of State Key Laboratory of Coal Mine Disaster Dynamics and Control(2011DA105287-FW202303).
文摘As energy demand increases,the depth of mining is increasing,and methane disasters grow more serious,efficient extraction of methane is the ultimate method of preventing and controlling methane disasters.The objectives for this research are to explore the efficiency of N_(2) injection to enhance gas extraction from coal seams(N_(2)-ECGE)and its impact on coal seam permeability.By developing a fluid-solid coupling model and using COMSOL Multiphysics to perform numerical simulations,the changes in gas pressure,methane content,gas production,output rate and permeability of coal seams were comparatively analyzed under the two methods of direct extraction and N_(2)-ECGE.The research results show that N_(2)-ECGE can significantly improve the coal seam gas pressure and reduce the coal seam CH_(4) content,and the larger the N_(2) injection pressure the more significant the reduction effect.Meanwhile,N_(2)-ECGE can significantly increase the CH_(4) extraction and output rate,and the increase of N_(2) pressure further improves the extraction efficiency.In addition,the pressure of nitrogen injection has a remarkable effect on coal seam permeability,high pressure of nitrogen injection can increase the permeability in the time of no disturbance,but the rate of permeability decreases more quickly after disturbed.The effect of strain due to adsorption desorption on coal seam permeability dominates.Despite model construction limitations,this research offers essential theoretical and practical direction for N_(2) injection to enhance the permeability evolution law of coal seam gas extraction process.
基金financially supported by the National Natural Science Foundation of China National Outstanding Youth Science Fund Project (Grant No. 52222109)the National Natural Science Foundation of China (Grant No. 52201322)+1 种基金Guangdong Basic and Applied Basic Research Foundation (Grant Nos. 2024A1515240006, 2022B1515020036 and 2023A1515012144)the Project of State Key Laboratory of Subtropical Building and Urban Science (Grant No. 2023ZB14)。
文摘The integrated system composed of wave energy converters and floating wind turbines offers substantial potential for reducing the levelized cost of energy(LCOE) by sharing the infrastructure, mooring system, substations and cables.This paper proposes an integrated system consisting of a semi-submersible wind turbine platform and three Wave Star flap-type wave energy converters. The coupled motion model of the integrated system is established and validated on the basis of viscously corrected potential flow theory. This study investigates the influence of two key parameters,the arm length and hinge points of flap-type wave energy converters, on system performance. The results reveal that variations in the arm length of flap-type wave energy converters(WECs) are the primary determinants of the integrated system's dynamic characteristics, whereas changes in hinge points predominantly affect device power generation.Additionally, incorporating WECs reduces the pitch and heave motions of the platform within a specific wave frequency range, thereby enhancing the energy output of the integrated system at the operational sea site. The performance of this hybrid system at a selected sea site is further assessed via the proposed aero-hydroservo coupling simulations.
基金supported by the National Natural Science Foundation of China(Grant Nos.U2141254 and U23B6009)。
文摘In this paper,a high-fidelity computational fluid dynamics(CFD)and rigid body dynamics(RBD)coupled platform for virtual flight simulation is developed to investigate the flight stability of fixed canard dual-spin projectile.The platform's reliability is validated by reproducing the characteristic resonance instability of such projectiles.By coupling the solution of the Unsteady Reynolds-Averaged Navier-Stokes equations and the seven-degree-of-freedom RBD equations,the virtual flight simulations of fixed canard dual-spin projectiles at various curvature trajectories are achieved,and the dynamic mechanism of the trajectory following process is analyzed.The instability mechanism of the dynamic instability during trajectory following process of the fixed canard dual-spin projectile is elucidated by simulating the rolling/coning coupled forced motion,and subsequently validated through virtual flight simulations.The findings suggest that an appropriate yaw moment can drive the projectile axis to precession in the tangential direction of the trajectory,thereby enhancing the trajectory following stability.However,the damping of the projectile attains its minimum value when the forward body equilibrium rotational speed(-128 rad/s)is equal to the negative of the fast mode frequency of the projectile.Insufficient damping leads to the fixed canard dual-spin projectile exiting the dynamic stability domain during the trajectory following,resulting in weakly damped instability.Keeping the forward body not rotating or increasing the spin rates to-192 rad/s can enhance the projectile's damping,thereby improving its dynamic stability.
