Clarifying the gas ingestion mechanism in the turbine disc cavity of marine gas turbines is crucial for ensuring the normal operation of turbines.However, the ingestion is influenced by factors such as the rotational ...Clarifying the gas ingestion mechanism in the turbine disc cavity of marine gas turbines is crucial for ensuring the normal operation of turbines.However, the ingestion is influenced by factors such as the rotational pumping effect, mainstream pressure asymmetry, rotor–stator interaction,and unsteady flow structures, complicating the flow. To investigate the impact of rotor–stator interaction on ingestion, this paper decouples the model to include only the mainstream. This research employs experiments and numerical simulations to examine the effects of varying the flow coefficient through changes in rotational speed and mainstream flow rate. The main objective is to understand the influence of different rotor–stator interactions on the mainstream pressure field, accompanied by mechanistic explanations. The findings reveal inconsistent effects of the two methods for changing the flow coefficient on the mainstream pressure field. Particularly, the pressure distribution on the vane side primarily depends on the mainstream flow rate, while the pressure on the blade side is influenced by the mainstream flow rate and the attack angle represented by the flow coefficient. A larger angle of attack angle can increase pressure on the blade side, even surpassing the pressure on the vane side. Assessing the degree of mainstream pressure unevenness solely based on the pressure difference on the vane side is insufficient. This research provides a basis for subsequent studies on the influence of coupled real turbine rotor–stator interaction on gas ingestion.展开更多
The coupled nonlocal nonlinear Schrödinger equations with variable coefficients are researched using the nonstandard Hirota bilinear method.The two-soliton and double-hump one-soliton solutions for the equations ...The coupled nonlocal nonlinear Schrödinger equations with variable coefficients are researched using the nonstandard Hirota bilinear method.The two-soliton and double-hump one-soliton solutions for the equations are first obtained.By assigning different functions to the variable coefficients,we obtain V-shaped,Y-shaped,wave-type,exponential solitons,and so on.Next,we reveal the influence of the real and imaginary parts of the wave numbers on the double-hump structure based on the soliton solutions.Finally,by setting different wave numbers,we can change the distance and transmission direction of the solitons to analyze their dynamic behavior during collisions.This study establishes a theoretical framework for controlling the dynamics of optical fiber in nonlocal nonlinear systems.展开更多
For a variable coefficient Kadomtsev-Petviashvili(KP)equation the Lax pair as well as conjugate Lax pair are derived from the Painleve analysis.The N-fold binary Darboux transformation is presented in a compact form.A...For a variable coefficient Kadomtsev-Petviashvili(KP)equation the Lax pair as well as conjugate Lax pair are derived from the Painleve analysis.The N-fold binary Darboux transformation is presented in a compact form.As an application,the multi-lump,higher-order lump and general lump-soliton interaction solutions for the variable coefficient KP equation are obtained.Typical lump structures with amplitudes exponentially decaying to zero as the time tends to infinity and interactions between one lump and one soliton are shown.展开更多
The parallel processing based on the free running model test was adopted to predict the interaction force coefficients （flow straightening coefficient and wake fraction） of ship maneuvering. And the multipopulation ...The parallel processing based on the free running model test was adopted to predict the interaction force coefficients （flow straightening coefficient and wake fraction） of ship maneuvering. And the multipopulation genetic algorithm （MPGA） based on real coding that can contemporarily process the data of free running model and simulation of ship maneuvering was applied to solve the problem. Accordingly the optimal individual was obtained using the method of genetic algorithm. The parallel processing of multiopulation solved the prematurity in the identification for single population, meanwhile, the parallel processing of the data of ship maneuvering （turning motion and zigzag motion） is an attempt to solve the coefficient drift problem. In order to validate the method, the interaction force coefficients were verified by the procedure and these coefficients measured were compared with those ones identified. The maximum error is less than 5%, and the identification is an effective method.展开更多
Solubility of Ca in manganese and manganese alloys was measured under sealed conditions at 1350℃.The interaction coefficients of Al and Fe on Ca in Mn were evaluated with the exper- imental data.The standard free ene...Solubility of Ca in manganese and manganese alloys was measured under sealed conditions at 1350℃.The interaction coefficients of Al and Fe on Ca in Mn were evaluated with the exper- imental data.The standard free energy of liquid Ca in liquid Mn based on the 1 wt-% solu- tion standard was estimated as well.展开更多
The interaction coefficients of Ca.Ti and Mg in the dilute Sn-based solution have been de- termined at 1500℃.Experimental measurements were taken by equilibrating the slag-alloy systems with metallic Sn as flux and g...The interaction coefficients of Ca.Ti and Mg in the dilute Sn-based solution have been de- termined at 1500℃.Experimental measurements were taken by equilibrating the slag-alloy systems with metallic Sn as flux and graphite as reducing agent under Ar atmosphere mixed with different portion of CO.It was found that a considerable error may produce if the coefficients of ε_(Ca)^(Ca),ε_(Mg)^(Mg)and ε_(Ti)^(Ti)in the molten Sn were neglected when the activities of the components CaO,MgO and TiO_2 in the slags were estimated by this method.展开更多
Based on Miedema's semiempirical formation enthalpy model for binary alloys, free volume theory and ageneral solution model, a new model for prediction of activity interaction coefficient ε is proposed. The calcu...Based on Miedema's semiempirical formation enthalpy model for binary alloys, free volume theory and ageneral solution model, a new model for prediction of activity interaction coefficient ε is proposed. The calculatedresults are better in agreement with the experimental values than the two previous models. The related theories andmodels are discussed according to the degree of agreement with experimental values.展开更多
Based on a single ion model, Hamiltonian of the simplest form about magnetocrystalline anisotropy for Tb3+ ion was solved by using the numerical method. The relation between the stabilization energy, crystal field coe...Based on a single ion model, Hamiltonian of the simplest form about magnetocrystalline anisotropy for Tb3+ ion was solved by using the numerical method. The relation between the stabilization energy, crystal field coefficient B20 and the magnetic exchange interaction was studied as temperature approaches to 0 K. The results show that the stabilization energy contributed by Tb3+ is linear with crystal field coefficient B20 approximately, but it is insensitive to the change of magnetic exchange interaction for the strong magnetic substances such as TbCo5, Tb2Co17 and Tb2Fe14B compounds.展开更多
It is very difficult,for the component-type ship mathematical model,to estimate the interaction force coefficients among the hull,propeller and rudder. Some coefficients such as wake fraction and flow straightening co...It is very difficult,for the component-type ship mathematical model,to estimate the interaction force coefficients among the hull,propeller and rudder. Some coefficients such as wake fraction and flow straightening coefficient were studied from the model tests in diffierent loading conditions and the normal force of rudder was tested in captive model tests to obtain the coefficients. From these results of the tests,the flow straightening coefficients increase with the increase of trims or drafts. Similarly,wake fraction coefficients are larger for the large drafts,however,become small as the trims increase. The resistance is obviously different in fully loaded condition with the trims by stern,however ,the difference is not evident when the draft decreases and the bulbous bow is above the water surface.展开更多
The time-resolved attenuated total reflectance-Fourier transform infrared(ATR-FTIR)spectroscopy is employed to investigate the transport mechanism of gel electrolytes by monitoring the diffusion behavior of propylene ...The time-resolved attenuated total reflectance-Fourier transform infrared(ATR-FTIR)spectroscopy is employed to investigate the transport mechanism of gel electrolytes by monitoring the diffusion behavior of propylene carbonate-lithium bis(trifluoromethylsulfonyl)imide(PC-LiTFSI)solution through poly(vinylidene fluoride-co-hexafluoropropylene)(P(VDF-HFP))films.Fickian behavior has been observed for both TFSr and PC.Higher temperature leads to faster diffusion of TFSI'and PC,which could be related to the increased free volume in P(VDF-HFP)matrix and rapid molecular movements upon heating.Various molecular interactions among LiTFSI,PC and P(VDF-HFP)have been recognized.During the diffusion process,PC molecules,in the form of small clusters,can firstly diffuse through the P(VDF-HFP)film and interact with P(VDF-HFP)by dipole-dipole interaction,acting as the plasticizer.Then,Li+diffuses into P(VDF-HFP)with the help of ion-dipole interactions between Li+and C=0 of PC.Meanwhile,TFSI-diffuses through the polymer matrix in solvation states.In addition,slight ion-dipole interactions between Li+and P(VDF-HFP)have been observed as well.Results in this work contribute to a better understanding of transport process in gel polymer electrolytes for lithium-ion batteries and support the development of improved gel polymer electrolytes by rationally regulating molecular interactions.展开更多
Activitibs of Si in binary Cu-Si and ternary Cu-Ti-Si melts were measured at 1 550℃ by using a method of chemical equilIbrium between gas and liquid. The activity interaction coefficients of Si in the melts have been...Activitibs of Si in binary Cu-Si and ternary Cu-Ti-Si melts were measured at 1 550℃ by using a method of chemical equilIbrium between gas and liquid. The activity interaction coefficients of Si in the melts have been determined from the experimental data (lny = -5.69. s = 6.69. P2: = -26.22. E; =-43.96) and activity interaction coefficients of Ti in binary Cu-Ti melt at 1550℃ has been estimated from Sommer's data based on the regular solution model (lny =-1 .10. : = 2.95.p:=-2.10).展开更多
The effect of trace elements with zero self-interaction coefficient on crystallization temperature of iron carbon alloys was studied and the mathematic equation was developed based on thermodynamics in the present res...The effect of trace elements with zero self-interaction coefficient on crystallization temperature of iron carbon alloys was studied and the mathematic equation was developed based on thermodynamics in the present researeh. With the equation developed in this paper, the effects of nitrogen on crystallization temperature of Fe-3.45C-2.15Si0. 16Mn and Fe-3.45C-2. 15Si-0. 80Mn alloys were discussed.展开更多
Results of drag coefficient（CD） from field observations and laboratory wave tank experiments indicate that the operational wave model can overestimate wind energy input under high wind conditions. The wind-wave inte...Results of drag coefficient（CD） from field observations and laboratory wave tank experiments indicate that the operational wave model can overestimate wind energy input under high wind conditions. The wind-wave interaction source term in WAVEWATCH Ⅲ has been modified to examine its behavior with tropical cyclone wind forcing. Using high resolution wind input,numerical experiments under idealized wind field and tropical cyclone Bonnie（1998） were designed to evaluate performance of the modified models. Both experiments indicate that the modified models with reduced CD significantly decrease wind energy input into the wave model and then simulate lower significant wave height（SWH） than the original model. However,the effects on spatial distribution of SWH,mean wavelength,mean wave direction,and directional wave spectra are insignificant. Due to the reduced wind energy input,the idealized experiment shows that the modified models simulate lower SWH than the original model in all four quadrants. The decrease in the front quadrants is significantly larger than that in the rear quadrants;it is larger under higher winds than lower winds. The realistic experiment on tropical cyclone Bonnie shows that the modified model with the various downward trends of CD in high winds creates a simulation that agrees best with scanning radar altimeter observations.展开更多
Large eddy simulation is performed to study three-dimensional wave-current interaction with a square cylinder at different Reynolds numbers, ranging from 1,000 to 600,000. The Keulegan-Carpenter number is relevantly a...Large eddy simulation is performed to study three-dimensional wave-current interaction with a square cylinder at different Reynolds numbers, ranging from 1,000 to 600,000. The Keulegan-Carpenter number is relevantly a constant of 0.6 for all cases. The Strouhal number, the mean and the RMS values of the effective drag coefficient in the streamwise and transverse directions are computed for various Reynolds numbers, and the velocity of a rep- resentative point in the turbulent zone is simulated to find the turbulent feature. It is found that the wave-current interaction should be considered as three-dimensional flow when the Reynolds number is high; under wave-current effect, there exists a critical Reynolds number, and when the Reynolds number is smaller than the critical one, current effect on wave can be nearly neglected; conversely, with the Reynolds number increasing, wave-currentstructure interaction is sensitive to the Reynolds number.展开更多
The aim of this study was to determine the attenuation of gamma and X-rays with different energies caused by passage through different materials.To this end,different materials with a range of atomic numbers were chos...The aim of this study was to determine the attenuation of gamma and X-rays with different energies caused by passage through different materials.To this end,different materials with a range of atomic numbers were chosen to measure gamma and X-ray attenuation coefficients and to explore the mechanisms of interaction of gamma and X-rays with matter of various kinds.It is shown that the attenuation coefficients first decrease and then increase with increase in the radiation(photon)energy.The attenuation of gamma and X-rays passing through materials with high atomic number is greater than that in materials with low atomic number.The attenuation minimum is related to the atomic number of the irradiated materials.The larger the atomic number is,the lower the energy corresponding to attenuation minimum is.Photoelectric and Compton effects are the main processes when gamma rays pass through individual materials with high and low atomic numbers,respectively.Therefore,for radiotherapy and radiation protection,different methods should be considered and selected for the use of gamma and X-rays of different energies for use in different materials.展开更多
Time-dependent diffusion coefficient and conventional diffusion constant are calculated and analyzed to study diffusion of nanoparticles in polymer melts. A generalized Langevin equa- tion is adopted to describe the d...Time-dependent diffusion coefficient and conventional diffusion constant are calculated and analyzed to study diffusion of nanoparticles in polymer melts. A generalized Langevin equa- tion is adopted to describe the diffusion dynamics. Mode-coupling theory is employed to calculate the memory kernel of friction. For simplicity, only microscopic terms arising from binary collision and coupling to the solvent density fluctuation are included in the formalism. The equilibrium structural information functions of the polymer nanocomposites required by mode-coupling theory are calculated on the basis of polymer reference interaction site model with Percus-Yevick closure. The effect of nanoparticle size and that of the polymer size are clarified explicitly. The structural functions, the friction kernel, as well as the diffusion coefficient show a rich variety with varying nanoparticle radius and polymer chain length. We find that for small nanoparticles or short chain polymers, the characteristic short time non-Markov diffusion dynamics becomes more prominent, and the diffusion coefficient takes longer time to approach asymptotically the conventional diffusion constant. This constant due to the microscopic contributions will decrease with the increase of nanoparticle size, while increase with polymer size. Furthermore, our result of diffusion constant from mode- coupling theory is compared with the value predicted from the Stokes-Einstein relation. It shows that the microscopic contributions to the diffusion constant are dominant for small nanoparticles or long chain polymers. Inversely, when nanonparticle is big, or polymer chain is short, the hydrodynamic contribution might play a significant role.展开更多
The inflation of a five-ring cone parachute with the airflow velocity of 18 m/s is studied based on the simplified arbitrary Lagrange Euler （SALE）/fluid-structure interaction （FSI） method. The numerical results of...The inflation of a five-ring cone parachute with the airflow velocity of 18 m/s is studied based on the simplified arbitrary Lagrange Euler （SALE）/fluid-structure interaction （FSI） method. The numerical results of the canopy shape, stability, opening load, and drag area are obtained, and they are well consistent with the experimental data gained from wind tunnel tests. The method is then used to simulate the opening process under different velocities. It is found that the first load shock affected by the velocity often occurs at the end of the initial inflation stage. For the first time, the phenomena that the inflation distance proportion coefficient increases and the dynamic load coefficient decreases, respectively, with the increase in the velocity are revealed. The above proposed method is competent to solve the large deformation problem without empirial coefficients, and can collect more space-time details of fluid-structure-motion information when it is compared with the traditional method.展开更多
A method for analysing the vehicle-bridge interaction system with enhanced objectivity is proposed in the paper, which considers the time-variant and random characteristics and allows finding the power spectral densit...A method for analysing the vehicle-bridge interaction system with enhanced objectivity is proposed in the paper, which considers the time-variant and random characteristics and allows finding the power spectral densities(PSDs) of the system responses directly from the PSD of track irregularity. The pseudo-excitation method is adopted in the proposed framework, where the vehicle is modelled as a rigid body and the bridge is modelled using the finite element method. The vertical and lateral wheel-rail pseudo-excitations are established assuming the wheel and rail have the same displacement and using the simplified Kalker creep theory, respectively. The power spectrum function of vehicle and bridge responses is calculated by history integral. Based on the dynamic responses from the deterministic and random analyses of the interaction system, and the probability density functions for three safety factors(derailment coefficient, wheel unloading rate, and lateral wheel axle force) are obtained, and the probabilities of the safety factors exceeding the given limits are calculated. The proposed method is validated by Monte Carlo simulations using a case study of a high-speed train running over a bridge with five simply supported spans and four piers.展开更多
Understanding interactions between gas molecules and solid surface is key to the aerodynamic design of high-speed,high-altitude aerospace vehicles,but there is a large dispersion of gas-surface interaction parameters ...Understanding interactions between gas molecules and solid surface is key to the aerodynamic design of high-speed,high-altitude aerospace vehicles,but there is a large dispersion of gas-surface interaction parameters or namely accommodation coefficients.The uncertainty results partly from different considerations of the interaction between gas molecules in various experimental and numerical methods.In this study,effects of gas-gas molecules interaction are systematically discussed by comparing two different approaches of molecular dynamics simulation of high-speed argon molecules scattering on a graphite surface.The popularly-used“single scattering”approach repeats the scattering process of a single gas molecule without considering the gas-gas molecules interaction.The newly-developed“continual scattering”approach continually shoots gas molecules at the surface,considering collisions between gas molecules in addition to gas molecules’collisions with surface.Gas-surface interaction features in the two approaches are compared and discussed under various affecting factors including rarefaction degree,gas-surface interaction strength,surface temperature and incident velocity.It is shown that these two approaches usually produce different accommodation coefficients,and the corresponding mechanisms are explained.This study could help clarify some doubts about the selection of accommodation coefficients in engineering practice,and also provide an instruction on design of an appropriate molecular dynamics simulation approach.展开更多
[Introduction] Accurate calculation of the hydrodynamic coefficients for floating structures and the investigation of the flow field distribution around floating bodies on the marine free surface are essential for imp...[Introduction] Accurate calculation of the hydrodynamic coefficients for floating structures and the investigation of the flow field distribution around floating bodies on the marine free surface are essential for improving the engineering design and application of marine structures.[Method] This study utilized the computational fluid dynamics(CFD) approach and the Reynolds Averaged NavierStokes(RANS) method and considered the effects of viscosity and free surface interactions on the hydrodynamic behavior of floating structures.By employing the dynamic mesh technique,this study simulated the periodic movements of simplified three-dimensional(3D)shapes:spheres,cylinders,and cubes,which were representative of complex marine structures.The volume of fluid(VOF) method was leveraged to accurately track the nonlinear behavior of the free surface.In this analysis,the added mass and damping coefficients for the fundamental modes of motion(surge,heave,and roll) were calculated across a spectrum of frequencies,facilitating the fast determination of hydrodynamic forces and moments exerted on floating structures.[Result] The results of this study are not only consistent with the results of the 3D potential flow theory but also further reflect the role of viscosity.This method can be used for precise calculation of the hydrodynamic coefficients of floating structures and for describing the flow field of such structures in motion on a free surface.[Conclusion] The methodology presented goes beyond the traditional potential flow approach.展开更多
基金the National Natural Science Foundation Outstanding Youth Foundation (Grant No.52122603)the National Science and Technology Major Project (J2019-Ⅲ-0003–0046)。
文摘Clarifying the gas ingestion mechanism in the turbine disc cavity of marine gas turbines is crucial for ensuring the normal operation of turbines.However, the ingestion is influenced by factors such as the rotational pumping effect, mainstream pressure asymmetry, rotor–stator interaction,and unsteady flow structures, complicating the flow. To investigate the impact of rotor–stator interaction on ingestion, this paper decouples the model to include only the mainstream. This research employs experiments and numerical simulations to examine the effects of varying the flow coefficient through changes in rotational speed and mainstream flow rate. The main objective is to understand the influence of different rotor–stator interactions on the mainstream pressure field, accompanied by mechanistic explanations. The findings reveal inconsistent effects of the two methods for changing the flow coefficient on the mainstream pressure field. Particularly, the pressure distribution on the vane side primarily depends on the mainstream flow rate, while the pressure on the blade side is influenced by the mainstream flow rate and the attack angle represented by the flow coefficient. A larger angle of attack angle can increase pressure on the blade side, even surpassing the pressure on the vane side. Assessing the degree of mainstream pressure unevenness solely based on the pressure difference on the vane side is insufficient. This research provides a basis for subsequent studies on the influence of coupled real turbine rotor–stator interaction on gas ingestion.
基金supported by the National Key R&D Program of China(Grant No.2022YFA1604200)the National Natural Science Foundation of China(Grant No.12261131495)Institute of Systems Science,Beijing Wuzi University(Grant No.BWUISS21).
文摘The coupled nonlocal nonlinear Schrödinger equations with variable coefficients are researched using the nonstandard Hirota bilinear method.The two-soliton and double-hump one-soliton solutions for the equations are first obtained.By assigning different functions to the variable coefficients,we obtain V-shaped,Y-shaped,wave-type,exponential solitons,and so on.Next,we reveal the influence of the real and imaginary parts of the wave numbers on the double-hump structure based on the soliton solutions.Finally,by setting different wave numbers,we can change the distance and transmission direction of the solitons to analyze their dynamic behavior during collisions.This study establishes a theoretical framework for controlling the dynamics of optical fiber in nonlocal nonlinear systems.
基金the National Natural Science Foundation of China under Grant(11705290,11901538,11875126)the China Postdoctoral Science Foundation funded sixty-fourth batch(2018M640678)+1 种基金the Young Scholar Foundation of ZUT(2018XQG16)Training Plan for Key Young Teachers of Colleges and Universities in Henan Province(2019GGJS143)。
文摘For a variable coefficient Kadomtsev-Petviashvili(KP)equation the Lax pair as well as conjugate Lax pair are derived from the Painleve analysis.The N-fold binary Darboux transformation is presented in a compact form.As an application,the multi-lump,higher-order lump and general lump-soliton interaction solutions for the variable coefficient KP equation are obtained.Typical lump structures with amplitudes exponentially decaying to zero as the time tends to infinity and interactions between one lump and one soliton are shown.
基金the Knowledge-based Ship-designHyper-integrated Platform (KSHIP) of Ministry ofEducation, China
文摘The parallel processing based on the free running model test was adopted to predict the interaction force coefficients （flow straightening coefficient and wake fraction） of ship maneuvering. And the multipopulation genetic algorithm （MPGA） based on real coding that can contemporarily process the data of free running model and simulation of ship maneuvering was applied to solve the problem. Accordingly the optimal individual was obtained using the method of genetic algorithm. The parallel processing of multiopulation solved the prematurity in the identification for single population, meanwhile, the parallel processing of the data of ship maneuvering （turning motion and zigzag motion） is an attempt to solve the coefficient drift problem. In order to validate the method, the interaction force coefficients were verified by the procedure and these coefficients measured were compared with those ones identified. The maximum error is less than 5%, and the identification is an effective method.
文摘Solubility of Ca in manganese and manganese alloys was measured under sealed conditions at 1350℃.The interaction coefficients of Al and Fe on Ca in Mn were evaluated with the exper- imental data.The standard free energy of liquid Ca in liquid Mn based on the 1 wt-% solu- tion standard was estimated as well.
文摘The interaction coefficients of Ca.Ti and Mg in the dilute Sn-based solution have been de- termined at 1500℃.Experimental measurements were taken by equilibrating the slag-alloy systems with metallic Sn as flux and graphite as reducing agent under Ar atmosphere mixed with different portion of CO.It was found that a considerable error may produce if the coefficients of ε_(Ca)^(Ca),ε_(Mg)^(Mg)and ε_(Ti)^(Ti)in the molten Sn were neglected when the activities of the components CaO,MgO and TiO_2 in the slags were estimated by this method.
文摘Based on Miedema's semiempirical formation enthalpy model for binary alloys, free volume theory and ageneral solution model, a new model for prediction of activity interaction coefficient ε is proposed. The calculatedresults are better in agreement with the experimental values than the two previous models. The related theories andmodels are discussed according to the degree of agreement with experimental values.
文摘Based on a single ion model, Hamiltonian of the simplest form about magnetocrystalline anisotropy for Tb3+ ion was solved by using the numerical method. The relation between the stabilization energy, crystal field coefficient B20 and the magnetic exchange interaction was studied as temperature approaches to 0 K. The results show that the stabilization energy contributed by Tb3+ is linear with crystal field coefficient B20 approximately, but it is insensitive to the change of magnetic exchange interaction for the strong magnetic substances such as TbCo5, Tb2Co17 and Tb2Fe14B compounds.
基金the Foundation Item "Knowledge-based Ship-design Hyper-integrated Platform(KSHIP)" of Ministry of Education of China
文摘It is very difficult,for the component-type ship mathematical model,to estimate the interaction force coefficients among the hull,propeller and rudder. Some coefficients such as wake fraction and flow straightening coefficient were studied from the model tests in diffierent loading conditions and the normal force of rudder was tested in captive model tests to obtain the coefficients. From these results of the tests,the flow straightening coefficients increase with the increase of trims or drafts. Similarly,wake fraction coefficients are larger for the large drafts,however,become small as the trims increase. The resistance is obviously different in fully loaded condition with the trims by stern,however ,the difference is not evident when the draft decreases and the bulbous bow is above the water surface.
基金the National Natural Science Foundation of China(No.21803010,21991123 and 51733003)the Shanghai Sailing Program(No.18FY1401100).
文摘The time-resolved attenuated total reflectance-Fourier transform infrared(ATR-FTIR)spectroscopy is employed to investigate the transport mechanism of gel electrolytes by monitoring the diffusion behavior of propylene carbonate-lithium bis(trifluoromethylsulfonyl)imide(PC-LiTFSI)solution through poly(vinylidene fluoride-co-hexafluoropropylene)(P(VDF-HFP))films.Fickian behavior has been observed for both TFSr and PC.Higher temperature leads to faster diffusion of TFSI'and PC,which could be related to the increased free volume in P(VDF-HFP)matrix and rapid molecular movements upon heating.Various molecular interactions among LiTFSI,PC and P(VDF-HFP)have been recognized.During the diffusion process,PC molecules,in the form of small clusters,can firstly diffuse through the P(VDF-HFP)film and interact with P(VDF-HFP)by dipole-dipole interaction,acting as the plasticizer.Then,Li+diffuses into P(VDF-HFP)with the help of ion-dipole interactions between Li+and C=0 of PC.Meanwhile,TFSI-diffuses through the polymer matrix in solvation states.In addition,slight ion-dipole interactions between Li+and P(VDF-HFP)have been observed as well.Results in this work contribute to a better understanding of transport process in gel polymer electrolytes for lithium-ion batteries and support the development of improved gel polymer electrolytes by rationally regulating molecular interactions.
文摘Activitibs of Si in binary Cu-Si and ternary Cu-Ti-Si melts were measured at 1 550℃ by using a method of chemical equilIbrium between gas and liquid. The activity interaction coefficients of Si in the melts have been determined from the experimental data (lny = -5.69. s = 6.69. P2: = -26.22. E; =-43.96) and activity interaction coefficients of Ti in binary Cu-Ti melt at 1550℃ has been estimated from Sommer's data based on the regular solution model (lny =-1 .10. : = 2.95.p:=-2.10).
文摘The effect of trace elements with zero self-interaction coefficient on crystallization temperature of iron carbon alloys was studied and the mathematic equation was developed based on thermodynamics in the present researeh. With the equation developed in this paper, the effects of nitrogen on crystallization temperature of Fe-3.45C-2.15Si0. 16Mn and Fe-3.45C-2. 15Si-0. 80Mn alloys were discussed.
基金The National Natural Science Foundation of China under contract No. 40706008the Open Research Program of the Key Laboratory of Chinese Acadeing of Sciences for Tropical Marine Environmental Dynamics under contract No. LED0606+1 种基金the Shandong Province Natural Science Foundation of China under contract No. Z2008E02the National High Technology Research and Development Program ("863" Program) of China under contract No. 2008AA09A402
文摘Results of drag coefficient（CD） from field observations and laboratory wave tank experiments indicate that the operational wave model can overestimate wind energy input under high wind conditions. The wind-wave interaction source term in WAVEWATCH Ⅲ has been modified to examine its behavior with tropical cyclone wind forcing. Using high resolution wind input,numerical experiments under idealized wind field and tropical cyclone Bonnie（1998） were designed to evaluate performance of the modified models. Both experiments indicate that the modified models with reduced CD significantly decrease wind energy input into the wave model and then simulate lower significant wave height（SWH） than the original model. However,the effects on spatial distribution of SWH,mean wavelength,mean wave direction,and directional wave spectra are insignificant. Due to the reduced wind energy input,the idealized experiment shows that the modified models simulate lower SWH than the original model in all four quadrants. The decrease in the front quadrants is significantly larger than that in the rear quadrants;it is larger under higher winds than lower winds. The realistic experiment on tropical cyclone Bonnie shows that the modified model with the various downward trends of CD in high winds creates a simulation that agrees best with scanning radar altimeter observations.
基金supported by the National Natural Science Foundation of China (No. 51178397)Technological Research and Development Programs of the Ministry of Railways (No. 2010G004-L)
文摘Large eddy simulation is performed to study three-dimensional wave-current interaction with a square cylinder at different Reynolds numbers, ranging from 1,000 to 600,000. The Keulegan-Carpenter number is relevantly a constant of 0.6 for all cases. The Strouhal number, the mean and the RMS values of the effective drag coefficient in the streamwise and transverse directions are computed for various Reynolds numbers, and the velocity of a rep- resentative point in the turbulent zone is simulated to find the turbulent feature. It is found that the wave-current interaction should be considered as three-dimensional flow when the Reynolds number is high; under wave-current effect, there exists a critical Reynolds number, and when the Reynolds number is smaller than the critical one, current effect on wave can be nearly neglected; conversely, with the Reynolds number increasing, wave-currentstructure interaction is sensitive to the Reynolds number.
基金supported by the National Natural Science Foundation of China(Nos.11475013,11975040 and U1832130)
文摘The aim of this study was to determine the attenuation of gamma and X-rays with different energies caused by passage through different materials.To this end,different materials with a range of atomic numbers were chosen to measure gamma and X-ray attenuation coefficients and to explore the mechanisms of interaction of gamma and X-rays with matter of various kinds.It is shown that the attenuation coefficients first decrease and then increase with increase in the radiation(photon)energy.The attenuation of gamma and X-rays passing through materials with high atomic number is greater than that in materials with low atomic number.The attenuation minimum is related to the atomic number of the irradiated materials.The larger the atomic number is,the lower the energy corresponding to attenuation minimum is.Photoelectric and Compton effects are the main processes when gamma rays pass through individual materials with high and low atomic numbers,respectively.Therefore,for radiotherapy and radiation protection,different methods should be considered and selected for the use of gamma and X-rays of different energies for use in different materials.
基金This work was supported by the National Natural Science Foundation of China （No.21173152）, the Ministry of Education of China （No.NCET-11-0359 and No.2011SCU04B31）, and the Science and Technology Department of Sichuan Province （No.2011HH0005）.
文摘Time-dependent diffusion coefficient and conventional diffusion constant are calculated and analyzed to study diffusion of nanoparticles in polymer melts. A generalized Langevin equa- tion is adopted to describe the diffusion dynamics. Mode-coupling theory is employed to calculate the memory kernel of friction. For simplicity, only microscopic terms arising from binary collision and coupling to the solvent density fluctuation are included in the formalism. The equilibrium structural information functions of the polymer nanocomposites required by mode-coupling theory are calculated on the basis of polymer reference interaction site model with Percus-Yevick closure. The effect of nanoparticle size and that of the polymer size are clarified explicitly. The structural functions, the friction kernel, as well as the diffusion coefficient show a rich variety with varying nanoparticle radius and polymer chain length. We find that for small nanoparticles or short chain polymers, the characteristic short time non-Markov diffusion dynamics becomes more prominent, and the diffusion coefficient takes longer time to approach asymptotically the conventional diffusion constant. This constant due to the microscopic contributions will decrease with the increase of nanoparticle size, while increase with polymer size. Furthermore, our result of diffusion constant from mode- coupling theory is compared with the value predicted from the Stokes-Einstein relation. It shows that the microscopic contributions to the diffusion constant are dominant for small nanoparticles or long chain polymers. Inversely, when nanonparticle is big, or polymer chain is short, the hydrodynamic contribution might play a significant role.
基金supported by the National Natural Science Foundation of China(No.11172137)the Aeronautical Science Foundation of China(No.20122910001)
文摘The inflation of a five-ring cone parachute with the airflow velocity of 18 m/s is studied based on the simplified arbitrary Lagrange Euler （SALE）/fluid-structure interaction （FSI） method. The numerical results of the canopy shape, stability, opening load, and drag area are obtained, and they are well consistent with the experimental data gained from wind tunnel tests. The method is then used to simulate the opening process under different velocities. It is found that the first load shock affected by the velocity often occurs at the end of the initial inflation stage. For the first time, the phenomena that the inflation distance proportion coefficient increases and the dynamic load coefficient decreases, respectively, with the increase in the velocity are revealed. The above proposed method is competent to solve the large deformation problem without empirial coefficients, and can collect more space-time details of fluid-structure-motion information when it is compared with the traditional method.
文摘A method for analysing the vehicle-bridge interaction system with enhanced objectivity is proposed in the paper, which considers the time-variant and random characteristics and allows finding the power spectral densities(PSDs) of the system responses directly from the PSD of track irregularity. The pseudo-excitation method is adopted in the proposed framework, where the vehicle is modelled as a rigid body and the bridge is modelled using the finite element method. The vertical and lateral wheel-rail pseudo-excitations are established assuming the wheel and rail have the same displacement and using the simplified Kalker creep theory, respectively. The power spectrum function of vehicle and bridge responses is calculated by history integral. Based on the dynamic responses from the deterministic and random analyses of the interaction system, and the probability density functions for three safety factors(derailment coefficient, wheel unloading rate, and lateral wheel axle force) are obtained, and the probabilities of the safety factors exceeding the given limits are calculated. The proposed method is validated by Monte Carlo simulations using a case study of a high-speed train running over a bridge with five simply supported spans and four piers.
基金This work was supported by the National Natural Science Foundation of China(No.12072343).
文摘Understanding interactions between gas molecules and solid surface is key to the aerodynamic design of high-speed,high-altitude aerospace vehicles,but there is a large dispersion of gas-surface interaction parameters or namely accommodation coefficients.The uncertainty results partly from different considerations of the interaction between gas molecules in various experimental and numerical methods.In this study,effects of gas-gas molecules interaction are systematically discussed by comparing two different approaches of molecular dynamics simulation of high-speed argon molecules scattering on a graphite surface.The popularly-used“single scattering”approach repeats the scattering process of a single gas molecule without considering the gas-gas molecules interaction.The newly-developed“continual scattering”approach continually shoots gas molecules at the surface,considering collisions between gas molecules in addition to gas molecules’collisions with surface.Gas-surface interaction features in the two approaches are compared and discussed under various affecting factors including rarefaction degree,gas-surface interaction strength,surface temperature and incident velocity.It is shown that these two approaches usually produce different accommodation coefficients,and the corresponding mechanisms are explained.This study could help clarify some doubts about the selection of accommodation coefficients in engineering practice,and also provide an instruction on design of an appropriate molecular dynamics simulation approach.
文摘[Introduction] Accurate calculation of the hydrodynamic coefficients for floating structures and the investigation of the flow field distribution around floating bodies on the marine free surface are essential for improving the engineering design and application of marine structures.[Method] This study utilized the computational fluid dynamics(CFD) approach and the Reynolds Averaged NavierStokes(RANS) method and considered the effects of viscosity and free surface interactions on the hydrodynamic behavior of floating structures.By employing the dynamic mesh technique,this study simulated the periodic movements of simplified three-dimensional(3D)shapes:spheres,cylinders,and cubes,which were representative of complex marine structures.The volume of fluid(VOF) method was leveraged to accurately track the nonlinear behavior of the free surface.In this analysis,the added mass and damping coefficients for the fundamental modes of motion(surge,heave,and roll) were calculated across a spectrum of frequencies,facilitating the fast determination of hydrodynamic forces and moments exerted on floating structures.[Result] The results of this study are not only consistent with the results of the 3D potential flow theory but also further reflect the role of viscosity.This method can be used for precise calculation of the hydrodynamic coefficients of floating structures and for describing the flow field of such structures in motion on a free surface.[Conclusion] The methodology presented goes beyond the traditional potential flow approach.
