As antennas are inherently included recommended in Over-The-Air (OTA) testing, it is important to also consider realistic channel models for the multiple-input multiple-output (MIMO) device performance evaluation. Thi...As antennas are inherently included recommended in Over-The-Air (OTA) testing, it is important to also consider realistic channel models for the multiple-input multiple-output (MIMO) device performance evaluation. This paper aims to emulate realistic multi-Path propagation channels in terms of angles of arrivals (AoA) and cross-polarization ratio (XPR) with Rayleigh fading, inside an anechoic chamber, for antenna diversity measurements. In this purpose, a practical multi-probe anechoic chamber measurement system (MPAC) with 24 probe antennas (SATIMO SG24) has been used. However, the actual configuration of this system is not able to reproduce realistic channels. Therefore, a new method based on the control of the SG24 probes has been developed. At first time, this method has been validated numerically through the comparison of simulated and analytical AoA probability density distributions. At the second time, the performance of an antenna diversity system inside the SG24 has been performed in terms of the correlation coefficient and diversity gain (DG) using an antenna reference system. Simulated and measurements results have shown a good agreement.展开更多
The influence of different solution and aging conditions on the microstructure,impact toughness,and crack initiation and propagation mechanisms of the novel α+β titanium alloy Ti6422 was systematically investigated....The influence of different solution and aging conditions on the microstructure,impact toughness,and crack initiation and propagation mechanisms of the novel α+β titanium alloy Ti6422 was systematically investigated.By adjusting the furnace cooling time after solution treatment and the aging temperature,Ti6422 alloy samples were developed with a multi-level lamellar microstructure,in-cluding microscaleαcolonies and α_(p) lamellae,as well as nanoscale α_(s) phases.Extending the furnace cooling time after solution treatment at 920℃ for 1 h from 240 to 540 min,followed by aging at 600℃ for 6 h,increased the α_(p) lamella content,reduced the α_(s) phase content,expanded theαcolonies and α_(p) lamellae size,and improved the impact toughness from 22.7 to 53.8 J/cm^(2).Additionally,under the same solution treatment,raising the aging temperature from 500 to 700℃ resulted in a decrease in the α_(s) phase content and a growth in the thickness of the α_(p) lamella and α_(s) phase.The impact toughness increased significantly with these changes.Samples with high α_(p) lamellae content or large α_(s) phase size exhibited high crack initiation and propagation energies.Impact deformation caused severe kinking of the α_(p) lamellae in crack initiation and propagation areas,leading to a uniform and high-density kernel average misorientation(KAM)distribu-tion,enhancing plastic deformation coordination and uniformity.Moreover,the multidirectional arrangement of coarserαcolonies and α_(p) lamellae continuously deflect the crack propagation direction,inhibiting crack propagation.展开更多
Hydraulic stimulation technology is widely employed to enhance the permeability of geothermal reservoirs.Nevertheless,accurately predicting hydraulic fracture propagation in complex geological conditions remains chall...Hydraulic stimulation technology is widely employed to enhance the permeability of geothermal reservoirs.Nevertheless,accurately predicting hydraulic fracture propagation in complex geological conditions remains challenging,thereby hindering the effective utilization of existing natural fractures.In this study,a phase field model was developed utilizing the finite element method to examine the influence of fluid presence,stress conditions,and natural fractures on the initiation and propagation of hydraulic fractures.The model employs Biot's poroelasticity theory to establish the coupling between the displacement field and the fluid field,while the phase field theory is applied to simulate fracture behavior.The results show that whenσ_(x0)/σ_(y0)<3 or qf<20 kg/(m^(3)·s),the presence of natural fractures can alter the original propagation direction of hydraulic fractures.Conversely,in the absence of these conditions,the propagation path of natural fractures is predominantly influenced by the initial stress field.Furthermore,based on the analysis of breakdown pressure and damage area,the optimal intersection angle between natural fractures and hydraulic fractures is determined to range from 45°to 60°.Finally,once a dominant channel forms,initiating and propagating hydraulic fractures in other directions becomes increasingly difficult,even in highly fractured areas.This method tackles the challenges of initiating and propagating hydraulic fractures in complex geological conditions,providing a theoretical basis for optimizing Enhanced Geothermal System(EGS)projects.展开更多
Using the software ANSYS-19.2/Explicit Dynamics,this study performedfinite-element modeling of the large-diameter steel pipeline cross-section for the Beineu-Bozoy-Shymkent gas pipeline with a non-through straight crac...Using the software ANSYS-19.2/Explicit Dynamics,this study performedfinite-element modeling of the large-diameter steel pipeline cross-section for the Beineu-Bozoy-Shymkent gas pipeline with a non-through straight crack,strengthened by steel wire wrapping.The effects of the thread tensile force of the steel winding in the form of single rings at the crack edges and the wires with different winding diameters and pitches were also studied.The results showed that the strengthening was preferably executed at a minimum value of the thread tensile force,which was 6.4%more effective than that at its maximum value.The analysis of the influence of the winding dia-meters showed that the equivalent stresses increased by 32%from the beginning of the crack growth until the wire broke.The increment in winding diameter decelerated the disclosure of the edge crack and reduced its length by 8.2%.The analysis of the influence of the winding pitch showed that decreasing the distance between the winding turns also led to a 33.6%reduction in the length of the straight crack and a 7.9%reduction in the maximum stres-ses on the strengthened pipeline cross-section.The analysis of the temperature effect on the pipeline material,within a range from-40℃to+50℃,resulted in a crack length change of up to 5.8%.As the temperature dropped,the crack length decreased.Within such a temperature range,the maximum stresses were observed along the cen-tral area of the crack,which were equal to 413 MPa at+50℃and 440 MPa at-40℃.The results also showed that the presence of the steel winding in the pipeline significantly reduced the length of crack propagation up to 8.4 times,depending on the temperature effect and design parameters of prestressing.This work integrated the existing methods for crack localization along steel gas pipelines.展开更多
Prepulse combined hydraulic fracturing facilitates the development of fracture networks by integrating prepulse hydraulic loading with conventional hydraulic fracturing.The formation mechanisms of fracture networks be...Prepulse combined hydraulic fracturing facilitates the development of fracture networks by integrating prepulse hydraulic loading with conventional hydraulic fracturing.The formation mechanisms of fracture networks between hydraulic and pre-existing fractures under different prepulse loading parameters remain unclear.This research investigates the impact of prepulse loading parameters,including the prepulse loading number ratio(C),prepulse loading stress ratio(S),and prepulse loading frequency(f),on the formation of fracture networks between hydraulic and pre-existing fractures,using both experimental and numerical methods.The results suggest that low prepulse loading stress ratios and high prepulse loading number ratios are advantageous loading modes.Multiple hydraulic fractures are generated in the specimen under the advantageous loading modes,facilitating the development of a complex fracture network.Fatigue damage occurs in the specimen at the prepulse loading stage.The high water pressure at the secondary conventional hydraulic fracturing promotes the growth of hydraulic fractures along the damage zones.This allows the hydraulic fractures to propagate deeply and interact with pre-existing fractures.Under advantageous loading conditions,multiple hydraulic fractures can extend to pre-existing fractures,and these hydraulic fractures penetrate or propagate along pre-existing fractures.Especially when the approach angle is large,the damage range in the specimen during the prepulse loading stage increases,resulting in the formation of more hydraulic fractures.展开更多
The crack initiation and early propagation are of great significance to the overall fatigue life of material.In order to investigate the anisotropic fracture behavior of laser metal deposited Ti-6Al-4V alloy(LMD Ti64)...The crack initiation and early propagation are of great significance to the overall fatigue life of material.In order to investigate the anisotropic fracture behavior of laser metal deposited Ti-6Al-4V alloy(LMD Ti64)during the early stage,the fourpoint bending fatigue test was carried out on specimens of three different directions,as well as the forged specimens.The results indicate the anisotropic crack initiation and early propagation of LMD Ti64.The direction perpendicular to the deposition direction exhibits a better fatigue resistance than the other two.The crack initiation position and propagation path are dominated by the microstructure in the vicinity of U-notch.LMD Ti64 has a typical small crack effect,and the early crack propagation velocities in three directions are similar.Affected by the slip system of LMD Ti64,secondary cracks frequently occur,which are often found to have an angle of 60°to the main crack.The electron backscatter diffraction analysis indicates that LMD Ti64 has preferred orientations,i.e.,strong 0001//Z texture and 001//Z texture.Their crystallographic orientation will change as the direction of columnarβgrains turns over,resulting in the fatigue anisotropy of LMD Ti64 in crack initiation and early crack propagation process.展开更多
Multi-stage and multi-cluster fracturing(MMF)is a crucial technology in unconventional oil and gas development,aiming to enhance production by creating extensive fracture networks.However,achieving uniform expansion o...Multi-stage and multi-cluster fracturing(MMF)is a crucial technology in unconventional oil and gas development,aiming to enhance production by creating extensive fracture networks.However,achieving uniform expansion of multi-cluster hydraulic fractures(HFs)in MMF remains a significant challenge.Field practice has shown that the use of temporary plugging and diversion fracturing(TPDF)can promote the balanced expansion of multi-cluster HFs.This study conducted TPDF experiments using a true triaxial fracturing simulation system setting a horizontal well completion with multi-cluster jetting perforations to investigate the equilibrium initiation and extension of multi-cluster fractures.The influence of key parameters,including cluster spacing,fracturing fluid viscosity,differential stress,and fracturing fluid injection rate,on fracture initiation and propagation was systematically examined.The results indicate that while close-spaced multi-cluster fracturing significantly increases the number of HFs,it also leads to uneven extension of HFs in their propagation.In contrast,TPDF demonstrates effectiveness in mitigating uneven HF extension,increasing the number of HFs,and creating a larger stimulated reservoir volume,ultimately leading to improved oil and gas well productivity.Moreover,under conditions of high differential stress,the differential stress within the formation exerts a stronger guiding effect in HFs,which are more closely aligned with the minimum principal stress.Low-viscosity fluids facilitate rapid and extensive fracture propagation within the rock formation.High-volume fluid injection,on the other hand,more comprehensively fills the formation.Therefore,employing lowviscosity and high-volume fracturing is advantageous for the initiation and extension of multi-cluster HFs.展开更多
In this article,we have developed a new time-marching method to simulate sound and soliton propagation in homogeneous and heterogeneous media.The proposed time integration scheme can numerically preserve physical disp...In this article,we have developed a new time-marching method to simulate sound and soliton propagation in homogeneous and heterogeneous media.The proposed time integration scheme can numerically preserve physical dispersion over a wide wavenumber range and conserve energy while solving wave propagation problems.Here,the Fourier stability analysis has been used to assess the numerical properties of the developed method.The proposed numerical method’s dispersion and dissipation properties have also been compared with the classical fourth-order Runge-Kutta(RK4)method.Stability property contours for the newly proposed method display that the maximum allowable time step is at least five times higher than the RK4 method.The Fourier stability analysis also explains the dispersion error associated with the used spatio-temporal discretization schemes.It is observed that the dispersion error is significantly small for the proposed time integration schemes compared with the RK4 method.The proposed methods simulate sound propagation problems with fewer computational resources that otherwise demand high computational costs.The efficacy of the proposed time integration methods has been demonstrated by solving benchmark sound wave propagation problems.Moreover,to test the developed method’s efficiency and robustness,we have performed simulations of the sound wave propagation in a layered media,corner-edge model,and damped sine-Gordon equation.展开更多
The acoustic wave propagation in gas-saturated double-porosity materials composed of a microporous matrix and mesopores with arrays of plate-type resonators is investigated.A macroscopic description,established with t...The acoustic wave propagation in gas-saturated double-porosity materials composed of a microporous matrix and mesopores with arrays of plate-type resonators is investigated.A macroscopic description,established with the two-scale asymptotic homogenization method,evidences the combined effect of inner resonances on the acoustic properties of the respective effective visco-thermal fluid.One type of resonance originates from strong pore-scale fluid-structure interaction,while the other one arises from pressure diffusion.These phenomena respectively cause weakly and highly damped resonances,which are activated by internal momentum or mass sources,and can largely influence,depending on the material's morphology,either the effective fluid's dynamic density,compressibility,or both.We introduce semi-analytical models to illustrate the key effective properties of the studied multiscale metamaterials.The results provide insights for the bottom-up design of multiscale acoustic metamaterials with exotic behaviors,such as the negative,very slow,or supersonic phase velocity,as well as sub-wavelength bandgaps.展开更多
The approximately 3000 km long Tan-Lu fault zone(TLFZ)in East Asia is the longest continental strike-slip fault zone in the world and exemplifies how such a fault zone forms and propagates on a continental scale.Struc...The approximately 3000 km long Tan-Lu fault zone(TLFZ)in East Asia is the longest continental strike-slip fault zone in the world and exemplifies how such a fault zone forms and propagates on a continental scale.Structural and geochronological data from the TLFZ and surrounding regions indicate that the fault zone originated as NE/SW-striking sinistral ductile shear zones along an oblique continental convergence margin during the Triassic indentation collision between the North China Craton and the Yangtze Block.The Triassic fault zone,with a total length of about 720 km between the Dabie and Sulu orogens,exhibited an apparent sinistral offset of approximately 300 km along the TLFZ.The second stage of sinistral movement occurred in the earliest Late Jurassic,reactivating the pre-existing southern segment and propagating northwards to the southern coastline of present-day Bohai Bay,as well as forming a significant portion of the Dunhua-Mishan fault zone.The third stage of sinistral movement,in the earliest Early Cretaceous,was the most intense strike-slip movement of the Mesozoic,leading to the complete linkage of the TLFZ.This stage included further northward propagation of the southern-middle segment,both southward and northward propagation of the Dunhua-Mishan fault zone,as well as the formation of the entire Yilan-Yitong fault zone.The fourth stage,in the earliest Late Cretaceous,involved the reactivation of the entire TLFZ.Following its Triassic origin due to the indentation collision,the subduction of the Paleo-Pacific Plate and the subduction and closure of the Mongol-Okhotsk Ocean were responsible for the multi-stage sinistral movements from the Late Jurassic to the Cretaceous.The evolution of the TLFZ demonstrates that a continental-scale strike-slip fault zone(>1000 km long)forms through multiple stages of propagation and linkage in dynamic settings of plate convergence.展开更多
The southern part of East Siberia(SES)is highly vulnerable to flooding caused by the extreme precipitation events(EPEs)during summer.Building on previously detected EPEs in SES and Mongolia,we examined wave propagatio...The southern part of East Siberia(SES)is highly vulnerable to flooding caused by the extreme precipitation events(EPEs)during summer.Building on previously detected EPEs in SES and Mongolia,we examined wave propagation patterns for two periods:1982-98 and 1999-2019.Our analysis revealed distinct wave train configurations and geopotential anomalies preceding EPEs,with an increase in wave activity flux across the Northern Hemisphere,followed by a subsequent decrease during EPEs.Consequently,Eastern Siberia has experienced a significant rise in wave activity.Based on geopotential anomalies over Central Siberia accompanying EPEs,we identified two main types.The first,the ridge type,is predominant during the first period and features a meridional contrast with a positive geopotential(and temperature)anomaly over Central Siberia and a negative anomaly over the subtropical regions along the same longitude.The second type,termed the trough type,is more typical for the second period.It involves either a negative geopotential anomaly or the zonal proximity of positive and negative geopotential anomalies over Central Siberia.The trough type,marked by zonally oriented anomalies in geopotential and temperature,results in a more pronounced temperature decrease before EPEs and significant zonal temperature contrasts.Further,it is related to more stationary waves over Northern Eurasia,with persistent positive geopotential anomalies over Europe linked to quasi-stationary troughs over Central Siberia and positive anomalies east of Lake Baikal.Our findings align with shifts in boreal summer teleconnection patterns,reflecting significant changes in wave propagation patterns that have occurred since the late 1990s.展开更多
Coastal near-inertial waves are usually generated by storms passing offshore and/or nearshore,and modified by the presence of the coast.They can modify coastal currents and upper-layer velocity structures,thereby affe...Coastal near-inertial waves are usually generated by storms passing offshore and/or nearshore,and modified by the presence of the coast.They can modify coastal currents and upper-layer velocity structures,thereby affecting material transport and ecosystem processes in the coastal region.The propagation characteristics of coastal near-inertial waves(CNIWs)are investigated in this study by using the Regional Ocean Circulation Modelling System(ROMS)model,forced by wind fields incorporating an idealized wind model around the typhoon center and ERA5 wind reanalysis data from ECMWF(European Center of Meteorological Weather Forecasting)beyond the typhoon center,and with realistic bathymetric data near the Guangdong coast,China.Spatial coherence analysis reveals that near-inertial energy propagates shoreward and upward along middle layers,guided by the topography.Near the coast,energy is transmitted offshore due to the presence of the coastal wall.Calculations of energy transport flux and group velocity further elucidate the wave propagation patterns,showing that near-inertial energy propagates onshore during the typhoon passage and offshore afterward.A two-layer structure of energy flux,separated by the thermocline,is identified,with variations observed between successive inertial periods.The sensitivity of CNIWs’propagation to typhoon parameters is examined through 12 experiments.A 10%increase in maximum wind velocity(V_(max)),radius of maximum wind(R_(max)),and typhoon translation speed()lead to respective changes in energy flux(−5%to+25%)and group velocity(−1%to+0.4%),highlighting their impacts on the CNIWs’energy fluxes.This study is of importance to coastal dynamics and disaster management.展开更多
Many existing immune detection algorithms rely on a large volume of labeled self-training samples,which are often difficult to obtain in practical scenarios,thus limiting the training of detection models.Furthermore,n...Many existing immune detection algorithms rely on a large volume of labeled self-training samples,which are often difficult to obtain in practical scenarios,thus limiting the training of detection models.Furthermore,noise inherent in the samples can substantially degrade the detection accuracy of these algorithms.To overcome these challenges,we propose an immune generation algorithm that leverages clustering and a rebound mechanism for label propagation(LP-CRI).The dataset is randomly partitioned into multiple subsets,each of which undergoes clustering followed by label propagation and evaluation.The rebound mechanism assesses the model’s performance after propagation and determines whether to revert to its previous state,initiating a subsequent round of propagation to ensure stable and effective training.Experimental results demonstrate that the proposed method is both computationally efficient and easy to train,significantly enhancing detector performance and outperforming traditional immune detection algorithms.展开更多
Hydraulic fracture growth is significantly influenced by the minimum horizontal principal stress gradient and the fracturing fluid pressure gradient.However,these gradients are often neglected in scaled physical model...Hydraulic fracture growth is significantly influenced by the minimum horizontal principal stress gradient and the fracturing fluid pressure gradient.However,these gradients are often neglected in scaled physical modeling experiments due to difficulties in reproducing them.This study uses centrifugal hypergravity to simulate both gradients and investigate their effects on fracture propagation.Artificial mortar specimens(ϕ200 mm×400 mm)are fractured under 1g(normal gravity),50g,and 100g.Results show that compared to 1g,fractures under 50g and 100g exhibit increasingly uneven propagation,with higher g-values leading to greater asymmetry.To interpret this,a theoretical analysis based on fracture mechanics is conducted.When the fluid pressure gradient exceeds the stress gradient,a positive net gradient is generated,increasing net pressure at the lower fracture tip.This raises the stress intensity factor at the lower tip,promoting downward growth.As g increases,the disparity becomes more significant,resulting in greater fracture deviation.In conclusion,this study,for the first time,has verified and explained that the net gradient can change the propagation of hydraulic fractures,providing important guidance for wellbore placement under stress gradients.展开更多
Hydraulic fracture(HF)formed in rock significantly helps with the development of geo-energy and georesources.The HF formation condition was challenging to understand,with obscure rock micro-cracking mechanisms being a...Hydraulic fracture(HF)formed in rock significantly helps with the development of geo-energy and georesources.The HF formation condition was challenging to understand,with obscure rock micro-cracking mechanisms being a key factor.The rock micro-cracking mechanism under gradient pore water pressure was analyzed on the scale of mineral particles and it was combined with macroscopic boundary conditions of rock hydraulic fracturing,obtaining the propagation criterion of HF in rock based on the rock micro-cracking mechanism which was verified by experiment.The results show that the disturbed skeleton stress induced by the disturbance of gradient pore water pressure in rock equals the pore water pressure difference.The overall range of the defined mechanical shape factor a/b is around 1,but greater than0.5.Under the combined influence of pore water pressure differences and macroscopic boundary stresses on the rock micro-cracking,micro-cracks form among rock mineral particles,micro-cracks connect to form micro-hydraulic fracture surfaces,and micro-hydraulic fracture surfaces open to form macrohydraulic fractures.HF begins to form at the micro-cracking initiation pressure(MCIP),which was tested by keeping the HF tip near the initiation point.The theoretical value of MCIP calculated by the proposed propagation criterion is close to MCIP tested.展开更多
As the economy grows, environmental issues are becoming increasingly severe, making the promotion of green behavior more urgent. Information dissemination and policy regulation play crucial roles in influencing and am...As the economy grows, environmental issues are becoming increasingly severe, making the promotion of green behavior more urgent. Information dissemination and policy regulation play crucial roles in influencing and amplifying the spread of green behavior across society. To this end, a novel three-layer model in multilayer networks is proposed. In the novel model, the information layer describes green information spreading, the physical contact layer depicts green behavior propagation, and policy regulation is symbolized by an isolated node beneath the two layers. Then, we deduce the green behavior threshold for the three-layer model using the microscopic Markov chain approach. Moreover, subject to some individuals who are more likely to influence others or become green nodes and the limitations of the capacity of policy regulation, an optimal scheme is given that could optimize policy interventions to most effectively prompt green behavior.Subsequently, simulations are performed to validate the preciseness and theoretical results of the new model. It reveals that policy regulation can prompt the prevalence and outbreak of green behavior. Then, the green behavior is more likely to spread and be prevalent in the SF network than in the ER network. Additionally, optimal allocation is highly successful in facilitating the dissemination of green behavior. In practice, the optimal allocation strategy could prioritize interventions at critical nodes or regions, such as highly connected urban areas, where the impact of green behavior promotion would be most significant.展开更多
In this paper,we investigate the propagation of chaos for solutions to the Liouville equation derived from the Linear-Formation particle model.By imposing certain conditions,we derive the rate of convergence between t...In this paper,we investigate the propagation of chaos for solutions to the Liouville equation derived from the Linear-Formation particle model.By imposing certain conditions,we derive the rate of convergence between the k-tensor product f_(t)^(■k)of the solution to be Linear-Formation kinetic equation and the k-marginal f_(N,k)^(t)of the solution to the Liouville equation corresponding to the Linear-Formation particle model.Specifically,the following estimate holds in terms of p-Wasserstein(1≤p<∞)distance W_(p)^(p)(f_(t)^(■k),f_(N,k)^(t))≤C_(1)k/N^(min(p/2,1))(1+t^(p))e^(C_(2)^(t)),1≤k≤N.展开更多
In this paper,enhanced near-field shock wave propagation in underwater explosion is achieved by introducing a fragile air-tube under the explosive.Firstly,based on the ALE algorithm in the ANSYS/LS-DYNA software,a num...In this paper,enhanced near-field shock wave propagation in underwater explosion is achieved by introducing a fragile air-tube under the explosive.Firstly,based on the ALE algorithm in the ANSYS/LS-DYNA software,a numerical model integrating the water,the air,the explosive,and the air-tube is developed.Comparative discussion for explosion with air-tube in the air,as well as explosion in the water without air-tube,is made to highlight the distinct energy attenuation mechanism due to the introduction of the air-tube.Then,the influence of the tube geometry,as well as evolving structural boundaries,on the explosive process is discussed exhaustively.The results indicate that the air-tube acts as a shock focusing apparatus,significantly altering explosion flow dynamics.Tube damage mode relies on tube geometrical size.Time-refreshed structural boundary affects the position the fluid flowing into the air-tube,which in turn plays an impact on the bubble pattern and energy distribution near the tube outlet.Enhanced outlet pressure is strengthened along with the decrease of the outlet radius,cross-section height ratio and tube thickness.These insights offer valuable guidance for optimizing underwater explosion and possess prospectively scientific and practical significance.展开更多
This study presents a numerical analysis of the effects of a rigid flat wall with oscillating motion on the pressure wave propagation during a single spherical cavitation bubble collapse at different initial bubble po...This study presents a numerical analysis of the effects of a rigid flat wall with oscillating motion on the pressure wave propagation during a single spherical cavitation bubble collapse at different initial bubble positions.Different nondimensional distances S=0.8,0.9,1.0,1.1,1.2 and 1.3 were considered to investigate the effects of initial in-phase and out-of-phase oscillations of the flat wall.Numerical simulations of cavitation bubble collapse near an oscillating wall were conducted using a compressible two-phase flow model.This model incorporated the Volume of Fluid(VOF)interface-sharpening technique on a general curvilinear moving grid.The numerical results were consistent with published experimental data.The simulation examined the impact of oscillating walls on bubble behavior and the resulting pressure peaks observed on the wall surface.The numerical results demonstrate the significant impact of wall oscillation conditions on bubble collapse and migration behavior,and consequently,the generation of pressure waves with significantly different propagation and pressure peaks induced by shock impact on the rigid wall.Different behaviors were observed in the trendlines of the pressure peaks and maximum jet velocity under in-phase and out-of-phase oscillating walls,with distinct values.At S≥1.0,a higher-pressure peak on the wall was observed in the case of the out-of-phase oscillating condition,whereas a higher-pressure peak was found in the case of the in-phase condition at S<1.0.The highest-pressure peak was found at S=0.8 in trend lines of in-phase and S=1.1 in trend lines of out-of-phase oscillation effects.展开更多
The diversity of interlayers in shale oil reservoir leads to a low degree of vertical reconstruction.This paper aims to propose a method to guide the synchronous initiation of hydraulic fractures in different layers b...The diversity of interlayers in shale oil reservoir leads to a low degree of vertical reconstruction.This paper aims to propose a method to guide the synchronous initiation of hydraulic fractures in different layers by drilling multi-layer radial wells in spatial positions,and to form a fracture network that satisfies the vertical propagation range and complexity.In this paper,a 3D(three-dimensional)multi-layer radial well fracturing model considering fluid-mechanics coupling is established and the properties of shale oil reservoir are characterized according to the field geological profile.The influences of radial well spacing,fracturing fluid injection rate,and fracturing fluid viscosity on vertical fracture communication in multilayer radial wells are investigated.The results show that the radial well has the characteristics of guiding fracture penetrating interlayers.Reducing radial well spacing and appropriately increasing injection rate and viscosity are beneficial to improving vertical fracture propagation ability.However,high fracture fluid viscosity under the same displacement will lead to a significant increase in fracture aperture and weaken the total fracture area.In addition,if the stress interference around the radial wells is low,the radial well can be located in the middle of each layer to minimize the fracture height limitation.This study can provide a solution idea for vertical propagation limitation of hydraulic fractures in shale oil reservoir.展开更多
文摘As antennas are inherently included recommended in Over-The-Air (OTA) testing, it is important to also consider realistic channel models for the multiple-input multiple-output (MIMO) device performance evaluation. This paper aims to emulate realistic multi-Path propagation channels in terms of angles of arrivals (AoA) and cross-polarization ratio (XPR) with Rayleigh fading, inside an anechoic chamber, for antenna diversity measurements. In this purpose, a practical multi-probe anechoic chamber measurement system (MPAC) with 24 probe antennas (SATIMO SG24) has been used. However, the actual configuration of this system is not able to reproduce realistic channels. Therefore, a new method based on the control of the SG24 probes has been developed. At first time, this method has been validated numerically through the comparison of simulated and analytical AoA probability density distributions. At the second time, the performance of an antenna diversity system inside the SG24 has been performed in terms of the correlation coefficient and diversity gain (DG) using an antenna reference system. Simulated and measurements results have shown a good agreement.
基金supported by the National Natural Science Foundation of China(No.52090041).
文摘The influence of different solution and aging conditions on the microstructure,impact toughness,and crack initiation and propagation mechanisms of the novel α+β titanium alloy Ti6422 was systematically investigated.By adjusting the furnace cooling time after solution treatment and the aging temperature,Ti6422 alloy samples were developed with a multi-level lamellar microstructure,in-cluding microscaleαcolonies and α_(p) lamellae,as well as nanoscale α_(s) phases.Extending the furnace cooling time after solution treatment at 920℃ for 1 h from 240 to 540 min,followed by aging at 600℃ for 6 h,increased the α_(p) lamella content,reduced the α_(s) phase content,expanded theαcolonies and α_(p) lamellae size,and improved the impact toughness from 22.7 to 53.8 J/cm^(2).Additionally,under the same solution treatment,raising the aging temperature from 500 to 700℃ resulted in a decrease in the α_(s) phase content and a growth in the thickness of the α_(p) lamella and α_(s) phase.The impact toughness increased significantly with these changes.Samples with high α_(p) lamellae content or large α_(s) phase size exhibited high crack initiation and propagation energies.Impact deformation caused severe kinking of the α_(p) lamellae in crack initiation and propagation areas,leading to a uniform and high-density kernel average misorientation(KAM)distribu-tion,enhancing plastic deformation coordination and uniformity.Moreover,the multidirectional arrangement of coarserαcolonies and α_(p) lamellae continuously deflect the crack propagation direction,inhibiting crack propagation.
基金supported by the National Key Research and Development Program(2021YFB150740401)National Natural Science Foundation of China(42202336)the CAS Pioneer Hundred Talents Program in China(Y826031C01)。
文摘Hydraulic stimulation technology is widely employed to enhance the permeability of geothermal reservoirs.Nevertheless,accurately predicting hydraulic fracture propagation in complex geological conditions remains challenging,thereby hindering the effective utilization of existing natural fractures.In this study,a phase field model was developed utilizing the finite element method to examine the influence of fluid presence,stress conditions,and natural fractures on the initiation and propagation of hydraulic fractures.The model employs Biot's poroelasticity theory to establish the coupling between the displacement field and the fluid field,while the phase field theory is applied to simulate fracture behavior.The results show that whenσ_(x0)/σ_(y0)<3 or qf<20 kg/(m^(3)·s),the presence of natural fractures can alter the original propagation direction of hydraulic fractures.Conversely,in the absence of these conditions,the propagation path of natural fractures is predominantly influenced by the initial stress field.Furthermore,based on the analysis of breakdown pressure and damage area,the optimal intersection angle between natural fractures and hydraulic fractures is determined to range from 45°to 60°.Finally,once a dominant channel forms,initiating and propagating hydraulic fractures in other directions becomes increasingly difficult,even in highly fractured areas.This method tackles the challenges of initiating and propagating hydraulic fractures in complex geological conditions,providing a theoretical basis for optimizing Enhanced Geothermal System(EGS)projects.
基金funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan(Grant No.AP19680589).
文摘Using the software ANSYS-19.2/Explicit Dynamics,this study performedfinite-element modeling of the large-diameter steel pipeline cross-section for the Beineu-Bozoy-Shymkent gas pipeline with a non-through straight crack,strengthened by steel wire wrapping.The effects of the thread tensile force of the steel winding in the form of single rings at the crack edges and the wires with different winding diameters and pitches were also studied.The results showed that the strengthening was preferably executed at a minimum value of the thread tensile force,which was 6.4%more effective than that at its maximum value.The analysis of the influence of the winding dia-meters showed that the equivalent stresses increased by 32%from the beginning of the crack growth until the wire broke.The increment in winding diameter decelerated the disclosure of the edge crack and reduced its length by 8.2%.The analysis of the influence of the winding pitch showed that decreasing the distance between the winding turns also led to a 33.6%reduction in the length of the straight crack and a 7.9%reduction in the maximum stres-ses on the strengthened pipeline cross-section.The analysis of the temperature effect on the pipeline material,within a range from-40℃to+50℃,resulted in a crack length change of up to 5.8%.As the temperature dropped,the crack length decreased.Within such a temperature range,the maximum stresses were observed along the cen-tral area of the crack,which were equal to 413 MPa at+50℃and 440 MPa at-40℃.The results also showed that the presence of the steel winding in the pipeline significantly reduced the length of crack propagation up to 8.4 times,depending on the temperature effect and design parameters of prestressing.This work integrated the existing methods for crack localization along steel gas pipelines.
基金financially supported by,the Fundamental Research Funds for the Central Universities(Grant No.2023QN1064)the China Postdoctoral Science Foundation(Grant No.2023M733772)Jiangsu Funding Program for Excellent Postdoctoral Talent(Grant No.2023ZB847)。
文摘Prepulse combined hydraulic fracturing facilitates the development of fracture networks by integrating prepulse hydraulic loading with conventional hydraulic fracturing.The formation mechanisms of fracture networks between hydraulic and pre-existing fractures under different prepulse loading parameters remain unclear.This research investigates the impact of prepulse loading parameters,including the prepulse loading number ratio(C),prepulse loading stress ratio(S),and prepulse loading frequency(f),on the formation of fracture networks between hydraulic and pre-existing fractures,using both experimental and numerical methods.The results suggest that low prepulse loading stress ratios and high prepulse loading number ratios are advantageous loading modes.Multiple hydraulic fractures are generated in the specimen under the advantageous loading modes,facilitating the development of a complex fracture network.Fatigue damage occurs in the specimen at the prepulse loading stage.The high water pressure at the secondary conventional hydraulic fracturing promotes the growth of hydraulic fractures along the damage zones.This allows the hydraulic fractures to propagate deeply and interact with pre-existing fractures.Under advantageous loading conditions,multiple hydraulic fractures can extend to pre-existing fractures,and these hydraulic fractures penetrate or propagate along pre-existing fractures.Especially when the approach angle is large,the damage range in the specimen during the prepulse loading stage increases,resulting in the formation of more hydraulic fractures.
基金National Natural Science Foundation of China(12172292,12072287)。
文摘The crack initiation and early propagation are of great significance to the overall fatigue life of material.In order to investigate the anisotropic fracture behavior of laser metal deposited Ti-6Al-4V alloy(LMD Ti64)during the early stage,the fourpoint bending fatigue test was carried out on specimens of three different directions,as well as the forged specimens.The results indicate the anisotropic crack initiation and early propagation of LMD Ti64.The direction perpendicular to the deposition direction exhibits a better fatigue resistance than the other two.The crack initiation position and propagation path are dominated by the microstructure in the vicinity of U-notch.LMD Ti64 has a typical small crack effect,and the early crack propagation velocities in three directions are similar.Affected by the slip system of LMD Ti64,secondary cracks frequently occur,which are often found to have an angle of 60°to the main crack.The electron backscatter diffraction analysis indicates that LMD Ti64 has preferred orientations,i.e.,strong 0001//Z texture and 001//Z texture.Their crystallographic orientation will change as the direction of columnarβgrains turns over,resulting in the fatigue anisotropy of LMD Ti64 in crack initiation and early crack propagation process.
基金funded by the National Natural Science Foundation of China(52104046).
文摘Multi-stage and multi-cluster fracturing(MMF)is a crucial technology in unconventional oil and gas development,aiming to enhance production by creating extensive fracture networks.However,achieving uniform expansion of multi-cluster hydraulic fractures(HFs)in MMF remains a significant challenge.Field practice has shown that the use of temporary plugging and diversion fracturing(TPDF)can promote the balanced expansion of multi-cluster HFs.This study conducted TPDF experiments using a true triaxial fracturing simulation system setting a horizontal well completion with multi-cluster jetting perforations to investigate the equilibrium initiation and extension of multi-cluster fractures.The influence of key parameters,including cluster spacing,fracturing fluid viscosity,differential stress,and fracturing fluid injection rate,on fracture initiation and propagation was systematically examined.The results indicate that while close-spaced multi-cluster fracturing significantly increases the number of HFs,it also leads to uneven extension of HFs in their propagation.In contrast,TPDF demonstrates effectiveness in mitigating uneven HF extension,increasing the number of HFs,and creating a larger stimulated reservoir volume,ultimately leading to improved oil and gas well productivity.Moreover,under conditions of high differential stress,the differential stress within the formation exerts a stronger guiding effect in HFs,which are more closely aligned with the minimum principal stress.Low-viscosity fluids facilitate rapid and extensive fracture propagation within the rock formation.High-volume fluid injection,on the other hand,more comprehensively fills the formation.Therefore,employing lowviscosity and high-volume fracturing is advantageous for the initiation and extension of multi-cluster HFs.
文摘In this article,we have developed a new time-marching method to simulate sound and soliton propagation in homogeneous and heterogeneous media.The proposed time integration scheme can numerically preserve physical dispersion over a wide wavenumber range and conserve energy while solving wave propagation problems.Here,the Fourier stability analysis has been used to assess the numerical properties of the developed method.The proposed numerical method’s dispersion and dissipation properties have also been compared with the classical fourth-order Runge-Kutta(RK4)method.Stability property contours for the newly proposed method display that the maximum allowable time step is at least five times higher than the RK4 method.The Fourier stability analysis also explains the dispersion error associated with the used spatio-temporal discretization schemes.It is observed that the dispersion error is significantly small for the proposed time integration schemes compared with the RK4 method.The proposed methods simulate sound propagation problems with fewer computational resources that otherwise demand high computational costs.The efficacy of the proposed time integration methods has been demonstrated by solving benchmark sound wave propagation problems.Moreover,to test the developed method’s efficiency and robustness,we have performed simulations of the sound wave propagation in a layered media,corner-edge model,and damped sine-Gordon equation.
基金Project supported by the Chilean National Agency for Research and Development(ANID)through Grants ANID FONDECYT Regular(Nos.1211310 and 1250496)ANID Anillo de Tecnologia(No.ACT240015)the Polish National Science Centre(NCN)through Grant Agreement(No.2021/41/B/ST8/04492)。
文摘The acoustic wave propagation in gas-saturated double-porosity materials composed of a microporous matrix and mesopores with arrays of plate-type resonators is investigated.A macroscopic description,established with the two-scale asymptotic homogenization method,evidences the combined effect of inner resonances on the acoustic properties of the respective effective visco-thermal fluid.One type of resonance originates from strong pore-scale fluid-structure interaction,while the other one arises from pressure diffusion.These phenomena respectively cause weakly and highly damped resonances,which are activated by internal momentum or mass sources,and can largely influence,depending on the material's morphology,either the effective fluid's dynamic density,compressibility,or both.We introduce semi-analytical models to illustrate the key effective properties of the studied multiscale metamaterials.The results provide insights for the bottom-up design of multiscale acoustic metamaterials with exotic behaviors,such as the negative,very slow,or supersonic phase velocity,as well as sub-wavelength bandgaps.
基金funded by the Ministry of Science and Technology of the People's Republic of China(Grant 2024ZD1001301)the National Natural Science Foundation of China(Grants 42272241,42102254 and 41830213)the Fundamental Research Funds for the Central Universities(Grant JZ2023HGTB0238).
文摘The approximately 3000 km long Tan-Lu fault zone(TLFZ)in East Asia is the longest continental strike-slip fault zone in the world and exemplifies how such a fault zone forms and propagates on a continental scale.Structural and geochronological data from the TLFZ and surrounding regions indicate that the fault zone originated as NE/SW-striking sinistral ductile shear zones along an oblique continental convergence margin during the Triassic indentation collision between the North China Craton and the Yangtze Block.The Triassic fault zone,with a total length of about 720 km between the Dabie and Sulu orogens,exhibited an apparent sinistral offset of approximately 300 km along the TLFZ.The second stage of sinistral movement occurred in the earliest Late Jurassic,reactivating the pre-existing southern segment and propagating northwards to the southern coastline of present-day Bohai Bay,as well as forming a significant portion of the Dunhua-Mishan fault zone.The third stage of sinistral movement,in the earliest Early Cretaceous,was the most intense strike-slip movement of the Mesozoic,leading to the complete linkage of the TLFZ.This stage included further northward propagation of the southern-middle segment,both southward and northward propagation of the Dunhua-Mishan fault zone,as well as the formation of the entire Yilan-Yitong fault zone.The fourth stage,in the earliest Late Cretaceous,involved the reactivation of the entire TLFZ.Following its Triassic origin due to the indentation collision,the subduction of the Paleo-Pacific Plate and the subduction and closure of the Mongol-Okhotsk Ocean were responsible for the multi-stage sinistral movements from the Late Jurassic to the Cretaceous.The evolution of the TLFZ demonstrates that a continental-scale strike-slip fault zone(>1000 km long)forms through multiple stages of propagation and linkage in dynamic settings of plate convergence.
文摘The southern part of East Siberia(SES)is highly vulnerable to flooding caused by the extreme precipitation events(EPEs)during summer.Building on previously detected EPEs in SES and Mongolia,we examined wave propagation patterns for two periods:1982-98 and 1999-2019.Our analysis revealed distinct wave train configurations and geopotential anomalies preceding EPEs,with an increase in wave activity flux across the Northern Hemisphere,followed by a subsequent decrease during EPEs.Consequently,Eastern Siberia has experienced a significant rise in wave activity.Based on geopotential anomalies over Central Siberia accompanying EPEs,we identified two main types.The first,the ridge type,is predominant during the first period and features a meridional contrast with a positive geopotential(and temperature)anomaly over Central Siberia and a negative anomaly over the subtropical regions along the same longitude.The second type,termed the trough type,is more typical for the second period.It involves either a negative geopotential anomaly or the zonal proximity of positive and negative geopotential anomalies over Central Siberia.The trough type,marked by zonally oriented anomalies in geopotential and temperature,results in a more pronounced temperature decrease before EPEs and significant zonal temperature contrasts.Further,it is related to more stationary waves over Northern Eurasia,with persistent positive geopotential anomalies over Europe linked to quasi-stationary troughs over Central Siberia and positive anomalies east of Lake Baikal.Our findings align with shifts in boreal summer teleconnection patterns,reflecting significant changes in wave propagation patterns that have occurred since the late 1990s.
基金The National Natural Science Foundation of China under contract No.42276169。
文摘Coastal near-inertial waves are usually generated by storms passing offshore and/or nearshore,and modified by the presence of the coast.They can modify coastal currents and upper-layer velocity structures,thereby affecting material transport and ecosystem processes in the coastal region.The propagation characteristics of coastal near-inertial waves(CNIWs)are investigated in this study by using the Regional Ocean Circulation Modelling System(ROMS)model,forced by wind fields incorporating an idealized wind model around the typhoon center and ERA5 wind reanalysis data from ECMWF(European Center of Meteorological Weather Forecasting)beyond the typhoon center,and with realistic bathymetric data near the Guangdong coast,China.Spatial coherence analysis reveals that near-inertial energy propagates shoreward and upward along middle layers,guided by the topography.Near the coast,energy is transmitted offshore due to the presence of the coastal wall.Calculations of energy transport flux and group velocity further elucidate the wave propagation patterns,showing that near-inertial energy propagates onshore during the typhoon passage and offshore afterward.A two-layer structure of energy flux,separated by the thermocline,is identified,with variations observed between successive inertial periods.The sensitivity of CNIWs’propagation to typhoon parameters is examined through 12 experiments.A 10%increase in maximum wind velocity(V_(max)),radius of maximum wind(R_(max)),and typhoon translation speed()lead to respective changes in energy flux(−5%to+25%)and group velocity(−1%to+0.4%),highlighting their impacts on the CNIWs’energy fluxes.This study is of importance to coastal dynamics and disaster management.
基金granted by Key Project of Beijing Municipal Social Science Foundation(No.15ZHA004)Key Project of Beijing Municipal Social Science Foundation and Beijing Municipal Education Commission Social Science Program(No.SZ20231123202).
文摘Many existing immune detection algorithms rely on a large volume of labeled self-training samples,which are often difficult to obtain in practical scenarios,thus limiting the training of detection models.Furthermore,noise inherent in the samples can substantially degrade the detection accuracy of these algorithms.To overcome these challenges,we propose an immune generation algorithm that leverages clustering and a rebound mechanism for label propagation(LP-CRI).The dataset is randomly partitioned into multiple subsets,each of which undergoes clustering followed by label propagation and evaluation.The rebound mechanism assesses the model’s performance after propagation and determines whether to revert to its previous state,initiating a subsequent round of propagation to ensure stable and effective training.Experimental results demonstrate that the proposed method is both computationally efficient and easy to train,significantly enhancing detector performance and outperforming traditional immune detection algorithms.
基金supports of Basic Science Center Program for Multiphase Evolution in Hyper-gravity of the National Natural Science Foundation of China(No.51988101)National Natural Science Foundation of China(Nos.52109138 and 52122403)Young Elite Scientists Sponsorship Program by CAST(No.2023QNRC001).
文摘Hydraulic fracture growth is significantly influenced by the minimum horizontal principal stress gradient and the fracturing fluid pressure gradient.However,these gradients are often neglected in scaled physical modeling experiments due to difficulties in reproducing them.This study uses centrifugal hypergravity to simulate both gradients and investigate their effects on fracture propagation.Artificial mortar specimens(ϕ200 mm×400 mm)are fractured under 1g(normal gravity),50g,and 100g.Results show that compared to 1g,fractures under 50g and 100g exhibit increasingly uneven propagation,with higher g-values leading to greater asymmetry.To interpret this,a theoretical analysis based on fracture mechanics is conducted.When the fluid pressure gradient exceeds the stress gradient,a positive net gradient is generated,increasing net pressure at the lower fracture tip.This raises the stress intensity factor at the lower tip,promoting downward growth.As g increases,the disparity becomes more significant,resulting in greater fracture deviation.In conclusion,this study,for the first time,has verified and explained that the net gradient can change the propagation of hydraulic fractures,providing important guidance for wellbore placement under stress gradients.
基金supported by the National Key Research and Development Program of China (No.2021YFC2902102)the National Natural Science Foundation of China (Nos.52374103 and 52274013)。
文摘Hydraulic fracture(HF)formed in rock significantly helps with the development of geo-energy and georesources.The HF formation condition was challenging to understand,with obscure rock micro-cracking mechanisms being a key factor.The rock micro-cracking mechanism under gradient pore water pressure was analyzed on the scale of mineral particles and it was combined with macroscopic boundary conditions of rock hydraulic fracturing,obtaining the propagation criterion of HF in rock based on the rock micro-cracking mechanism which was verified by experiment.The results show that the disturbed skeleton stress induced by the disturbance of gradient pore water pressure in rock equals the pore water pressure difference.The overall range of the defined mechanical shape factor a/b is around 1,but greater than0.5.Under the combined influence of pore water pressure differences and macroscopic boundary stresses on the rock micro-cracking,micro-cracks form among rock mineral particles,micro-cracks connect to form micro-hydraulic fracture surfaces,and micro-hydraulic fracture surfaces open to form macrohydraulic fractures.HF begins to form at the micro-cracking initiation pressure(MCIP),which was tested by keeping the HF tip near the initiation point.The theoretical value of MCIP calculated by the proposed propagation criterion is close to MCIP tested.
基金Project supported by the National Natural Science Foundation of China (Grant No. 62371253)the Postgraduate Research and Practice Innovation Program of Jiangsu Province, China (Grant No. KYCX24_1179)。
文摘As the economy grows, environmental issues are becoming increasingly severe, making the promotion of green behavior more urgent. Information dissemination and policy regulation play crucial roles in influencing and amplifying the spread of green behavior across society. To this end, a novel three-layer model in multilayer networks is proposed. In the novel model, the information layer describes green information spreading, the physical contact layer depicts green behavior propagation, and policy regulation is symbolized by an isolated node beneath the two layers. Then, we deduce the green behavior threshold for the three-layer model using the microscopic Markov chain approach. Moreover, subject to some individuals who are more likely to influence others or become green nodes and the limitations of the capacity of policy regulation, an optimal scheme is given that could optimize policy interventions to most effectively prompt green behavior.Subsequently, simulations are performed to validate the preciseness and theoretical results of the new model. It reveals that policy regulation can prompt the prevalence and outbreak of green behavior. Then, the green behavior is more likely to spread and be prevalent in the SF network than in the ER network. Additionally, optimal allocation is highly successful in facilitating the dissemination of green behavior. In practice, the optimal allocation strategy could prioritize interventions at critical nodes or regions, such as highly connected urban areas, where the impact of green behavior promotion would be most significant.
基金supported by the Natural Science Foundation of Hunan Province(2022JJ30655)the National Natural Science Foundation of China(12371180)the Training Program for Excellent Young Innovators of Changsha(kq2305046)。
文摘In this paper,we investigate the propagation of chaos for solutions to the Liouville equation derived from the Linear-Formation particle model.By imposing certain conditions,we derive the rate of convergence between the k-tensor product f_(t)^(■k)of the solution to be Linear-Formation kinetic equation and the k-marginal f_(N,k)^(t)of the solution to the Liouville equation corresponding to the Linear-Formation particle model.Specifically,the following estimate holds in terms of p-Wasserstein(1≤p<∞)distance W_(p)^(p)(f_(t)^(■k),f_(N,k)^(t))≤C_(1)k/N^(min(p/2,1))(1+t^(p))e^(C_(2)^(t)),1≤k≤N.
基金support from the National Natural Science Foundation of China(Grant No.12172040)is acknowledged.
文摘In this paper,enhanced near-field shock wave propagation in underwater explosion is achieved by introducing a fragile air-tube under the explosive.Firstly,based on the ALE algorithm in the ANSYS/LS-DYNA software,a numerical model integrating the water,the air,the explosive,and the air-tube is developed.Comparative discussion for explosion with air-tube in the air,as well as explosion in the water without air-tube,is made to highlight the distinct energy attenuation mechanism due to the introduction of the air-tube.Then,the influence of the tube geometry,as well as evolving structural boundaries,on the explosive process is discussed exhaustively.The results indicate that the air-tube acts as a shock focusing apparatus,significantly altering explosion flow dynamics.Tube damage mode relies on tube geometrical size.Time-refreshed structural boundary affects the position the fluid flowing into the air-tube,which in turn plays an impact on the bubble pattern and energy distribution near the tube outlet.Enhanced outlet pressure is strengthened along with the decrease of the outlet radius,cross-section height ratio and tube thickness.These insights offer valuable guidance for optimizing underwater explosion and possess prospectively scientific and practical significance.
基金sponsored by the Vietnam Academy of Science and Technology(VAST),granted to Prof.Duong Ngoc Hai under Project No.VAST01.02/22-23by the National Research Foundation(NRF)of the Republic of Korea,granted to Prof.Warn-Gyu Park under Project No.RS-2023-00248070.
文摘This study presents a numerical analysis of the effects of a rigid flat wall with oscillating motion on the pressure wave propagation during a single spherical cavitation bubble collapse at different initial bubble positions.Different nondimensional distances S=0.8,0.9,1.0,1.1,1.2 and 1.3 were considered to investigate the effects of initial in-phase and out-of-phase oscillations of the flat wall.Numerical simulations of cavitation bubble collapse near an oscillating wall were conducted using a compressible two-phase flow model.This model incorporated the Volume of Fluid(VOF)interface-sharpening technique on a general curvilinear moving grid.The numerical results were consistent with published experimental data.The simulation examined the impact of oscillating walls on bubble behavior and the resulting pressure peaks observed on the wall surface.The numerical results demonstrate the significant impact of wall oscillation conditions on bubble collapse and migration behavior,and consequently,the generation of pressure waves with significantly different propagation and pressure peaks induced by shock impact on the rigid wall.Different behaviors were observed in the trendlines of the pressure peaks and maximum jet velocity under in-phase and out-of-phase oscillating walls,with distinct values.At S≥1.0,a higher-pressure peak on the wall was observed in the case of the out-of-phase oscillating condition,whereas a higher-pressure peak was found in the case of the in-phase condition at S<1.0.The highest-pressure peak was found at S=0.8 in trend lines of in-phase and S=1.1 in trend lines of out-of-phase oscillation effects.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52074315 and 52122401)Moreover,the authors also thank the financial support from China Scholarship Council(Grant No.202306440033).
文摘The diversity of interlayers in shale oil reservoir leads to a low degree of vertical reconstruction.This paper aims to propose a method to guide the synchronous initiation of hydraulic fractures in different layers by drilling multi-layer radial wells in spatial positions,and to form a fracture network that satisfies the vertical propagation range and complexity.In this paper,a 3D(three-dimensional)multi-layer radial well fracturing model considering fluid-mechanics coupling is established and the properties of shale oil reservoir are characterized according to the field geological profile.The influences of radial well spacing,fracturing fluid injection rate,and fracturing fluid viscosity on vertical fracture communication in multilayer radial wells are investigated.The results show that the radial well has the characteristics of guiding fracture penetrating interlayers.Reducing radial well spacing and appropriately increasing injection rate and viscosity are beneficial to improving vertical fracture propagation ability.However,high fracture fluid viscosity under the same displacement will lead to a significant increase in fracture aperture and weaken the total fracture area.In addition,if the stress interference around the radial wells is low,the radial well can be located in the middle of each layer to minimize the fracture height limitation.This study can provide a solution idea for vertical propagation limitation of hydraulic fractures in shale oil reservoir.
