Combining Dual Reciprocity Method （DRM） with Hybrid Boundary Node Method （HBNM）, the Dual Reciprocity Hybrid Boundary Node Method （DRHBNM） is developed for three-dimensional linear elasticity problems with body ...Combining Dual Reciprocity Method （DRM） with Hybrid Boundary Node Method （HBNM）, the Dual Reciprocity Hybrid Boundary Node Method （DRHBNM） is developed for three-dimensional linear elasticity problems with body force. This method can be used to solve the elasticity problems with body force without domain integral, which is inevitable by HBNM. To demonstrate the versatility and the fast convergence of this method, some numerical examples of 3-D elasticity problems with body forces are examined. The computational results show that the present method is effective and can be widely applied in solving practical engineering problems.展开更多
This paper deals with a two-dimensional （2D） problem for a transverselyisotropic thick plate having heat sources and body forces. The upper surface of the plate is stress free with the prescribed surface temperature...This paper deals with a two-dimensional （2D） problem for a transverselyisotropic thick plate having heat sources and body forces. The upper surface of the plate is stress free with the prescribed surface temperature, while the lower surface of the plate rests on a rigid foundation and is thermally insulated. The study is carried out in the context of the generalized thermoelasticity proposed by Green and Naghdi. The governing equations for displacement and temperature fields are obtained in the Laplace-Fourier transform domain by applying the Laplace and Fourier transforms. The inversion of the double transform is done numerically. Numerical inversion of the Laplace transform is done based on the Fourier series expansion. Numerical computations are carried out for magnesium （Mg）, and the results are presented graphically. The results for an isotropic material （Cu） are obtained numerically and presented graphically to be compared with those of a transversely isotropic material （Mg）. The effect of the body forces is also studied.展开更多
Accurate prediction of the aerodynamic response of a compressor under inlet distortion is crucial for next-generation civil aircraft,such as Boundary Layer Ingestion(BLI)silent aircraft.Therefore,research on the Body ...Accurate prediction of the aerodynamic response of a compressor under inlet distortion is crucial for next-generation civil aircraft,such as Boundary Layer Ingestion(BLI)silent aircraft.Therefore,research on the Body Force(BF)model plays a significant role in achieving this objective.However,distorted inlet airflow can lead to varying operating conditions across different spatial locations of the compressor,which may cause some regions to operate outside the stability boundary.Consequently,the accuracy of BF model simulations might be compromised.To address this issue,this paper proposes a numerical simulation strategy for acquiring the steady axisymmetric three-dimensional flow field of a compressor operating at low mass flow rates,which is known as the Underlying Axisymmetric Pressure Rise Characteristic(UAPRC).The proposed simulation accounts for two different rotor speeds of a transonic compressor and identifies initial positions in the flow field where deterioration occurs based on prior experimental investigations.Moreover,simulation results are incorporated into the BF model to replicate hub instability observed in experiments.Obtained results demonstrate that this strategy provides valid predictions of the UAPRC of the compressor,thereby addressing the limitations associated with the BF model.展开更多
After measuring arc electrical current density distribution in gas tungsten arc welding(GTAW) with a probe method, the new expression of body force and model of LD10CS aluminum alloy weld pool are put forward for the ...After measuring arc electrical current density distribution in gas tungsten arc welding(GTAW) with a probe method, the new expression of body force and model of LD10CS aluminum alloy weld pool are put forward for the first time in GTAW with additional longitudinal magnetic field controlling. The influence of additional longitudinal magnetic field on body force is discussed by electromagnetic principle. This study provides the basis to study fluid flow of the weld pools and arc welding technique with electromagnetic controlling. [展开更多
As the environmental problems become increasingly serious,distributed electrical propulsion systems with higher aerodynamic efficiency and lower pollution emission have received extensive attention in recent years.The...As the environmental problems become increasingly serious,distributed electrical propulsion systems with higher aerodynamic efficiency and lower pollution emission have received extensive attention in recent years.The distributed electrical propulsion usually employs the new aero-propulsion integrated configuration.A simulation strategy for internal and external flow coupling based on the combination of lifting line theory and body force method is proposed.The lifting line theory and body force method as source term are embedded into the Navier-Stokes formulation.The lift and drag characteristics of the aero-propulsion coupling configuration are simulated.The results indicate that the coupling configuration has the most obvious lift augmentation at 12°angle of attack,which can provide an 11.11%increase in lift for the airfoil.At 0°angle of attack,the pressure difference on the lip parts provides the thrust component,which results in a lower drag coefficient.Additionally,the failure impact of a ducted fan at the middle or edge on aerodynamics is investigated.For the two failure conditions,the lift of the coupling configuration is decreased significantly by 27.85%and 26.14%respectively,and the lip thrust is decreased by 70.74%and 56.48%respectively.展开更多
To numerically study the impact of total temperature distortion on a transonic compressor with reduced computational costs,a Body-Force Model(BFM)is developed.Firstly,the interactions between the distorted flow and th...To numerically study the impact of total temperature distortion on a transonic compressor with reduced computational costs,a Body-Force Model(BFM)is developed.Firstly,the interactions between the distorted flow and the compressor are analyzed using full-annulus Unsteady Reynolds-Averaged Navier-Stokes(URANS)results and the orbit method.It is found that the induced swirl distortion and the mass flux nonuniformity are intensified in the compressor upstream flow field.A correction factor is thus added to the BFM to account for the effect of the induced swirl,which is crucial for the accurate representation of distortion transfer in the intake.Then,steady simulations with large-amplitude 180circumferential total temperature distortion are performed using the developed BFM.It is shown that the distorted compressor map simulated with the BFM matches well with URANS results.The circumferential phase shift of total temperature and the generation of the additional total pressure distortion across the rotor are in line with the time-averaged URANS flow field.The compressor upstream effects on the distorted inflow can also be exactly captured.All above-mentioned results demonstrate the BFM developed in this paper can effectively capture the distorted flow features inside the compressor,and significantly reduce the computational costs by five orders of magnitude compared with URANS.展开更多
A new finite difference lattice Boltzmann scheme is developed. Because of analyzing the influence of external body force roundly, the correct Navier-Stokes equations with the external body force are recovered, without...A new finite difference lattice Boltzmann scheme is developed. Because of analyzing the influence of external body force roundly, the correct Navier-Stokes equations with the external body force are recovered, without any additional unphysical terms. And some numerical results are presented. The result which close agreement with analytical data shows the good performance of the model.展开更多
The fracture behavior of superconducting tapes with central and edge oblique cracks subject to electromagnetic forces is investigated. Maxwell's equations and the critical state-Bean model are used to analytically...The fracture behavior of superconducting tapes with central and edge oblique cracks subject to electromagnetic forces is investigated. Maxwell's equations and the critical state-Bean model are used to analytically determine the magnetic flux density and electromagnetic force distributions in superconducting tapes containing central and edge oblique cracks. The distributed dislocation technique(DDT) transforms the mixed boundary value problem into a Cauchy singular integral equation, which is then solved by the Gauss-Chebyshev quadrature method to determine the stress intensity factors(SIFs).The model's accuracy is validated by comparing the calculated electromagnetic force distribution for the edge oblique crack and the SIFs for both crack types with the existing results. The findings indicate that the current and electromagnetic forces are significantly affected by the crack length and oblique angle. Specifically, for central oblique cracks, a smaller oblique angle enhances the risk of crack propagation, and a higher initial magnetization intensity poses greater danger under field cooling(FC) excitation. In contrast, for edge oblique cracks, a larger angle increases the likelihood of tape fractures. This study provides important insights into the fracture behavior and mechanical failure mechanisms of superconducting tapes with oblique cracks.展开更多
In this paper a nonlinear diffraction theory due to Stoke's 2nd-order wave for computing the wave force on the large body is presented. The radiation condition as r-∞ for 2nd-order scattered potential has been st...In this paper a nonlinear diffraction theory due to Stoke's 2nd-order wave for computing the wave force on the large body is presented. The radiation condition as r-∞ for 2nd-order scattered potential has been studied in connection with asymptotic solutions. A numerical procedure has been developed for the purpose of calculating the nonlinear wave force on the large body with arbitrary shape.展开更多
A coupled supersonic inlet-fan Navier–Stokes simulation method was developed by using COMSOL-CFD code. The flow turning, pressure rise and loss effects across blade rows of the fan and the inlet-fan interactions were...A coupled supersonic inlet-fan Navier–Stokes simulation method was developed by using COMSOL-CFD code. The flow turning, pressure rise and loss effects across blade rows of the fan and the inlet-fan interactions were taken into account as source terms of the governing equations without a blade geometry by a body force model. In this model, viscous effects in blade passages can also be calculated directly, which include the exchange of momentum between fluids and detailed viscous flow close to walls. NASA Rotor 37 compressor test rig was used to validate the ability of the body force model to estimate the real performance of blade rows. Calculated pressure ratio characteristics and the distribution of the total pressure, total temperature, and swirl angle in the span direction agreed well with experimental and numerical data. It is shown that the body force model is a promising approach for predicting the flow field of the turbomachinery. Then, coupled axisymmetric mixed compression supersonic inlet-fan simulations were conducted at Mach number 2.8 operating conditions. The analysis includes coupled steady-state performance, and effects of the fan on the inlet. The results indicate that the coupled simulation method is capable of simulating behavior of the supersonic inlet-fan system.展开更多
The flow over a short intake is characterised by a strong interaction with the fan, that can only be captured when the rotor blades are modelled in the numerical simulations. In this paper, we use a coupled methodolog...The flow over a short intake is characterised by a strong interaction with the fan, that can only be captured when the rotor blades are modelled in the numerical simulations. In this paper, we use a coupled methodology to derive indications about relevant geometric variables affecting the high-incidence operation of an ultra-high bypass ratio turbofan intake with a length-to-diameter ratio of 0.35. By reproducing the effect of the fan through a body force model, we carry out a parametric study of the influence of the contraction ratio and the scarf angle at take-off conditions for a grid of 28 different three-dimensional shapes. The analysis of the selected performance metrics distributions at three angles of attack of 16., 24., and 28. reveals that a contraction ratio higher than 1.20 is needed to avoid separation at high incidence. While for an attached inlet the best performance is found with a moderate scarf angle, in presence of a developed separation the distortion level reduces as the scarf decreases up to negative values. We discuss the correspondence between the distortion indexes and the flow field, highlighting the origin of the detachment for the different geometries, according to the operating condition, and analysing the fan operation in the most distorted case. Finally, we assess the influence of modelling the rotor in the simulations, showing that its suppression effect on the separation at a given incidence depends on the intake geometric features.展开更多
The electric-static body force model is obtained by solving Maxwell＇s electromagnetic equations. Based on the electro-static model, numerical modeling of flow around a cylinder with a dielectric barrier discharge （...The electric-static body force model is obtained by solving Maxwell＇s electromagnetic equations. Based on the electro-static model, numerical modeling of flow around a cylinder with a dielectric barrier discharge （DBD） plasma effect is also presented. The flow streamlines between the numerical simulation and the particle image velocimetry （PIV） experiment are consistent. According to the numerical simulation, DBD plasma can reduce the drag coefficient and change the vortex shedding frequencies of flow around tile cylinder.展开更多
Particle image velocimetry experiments and simulations were conducted in this study to clarify the influence of the DBD plasma actuator on the flow over a flat plate. The result shows that the actuator not only effect...Particle image velocimetry experiments and simulations were conducted in this study to clarify the influence of the DBD plasma actuator on the flow over a flat plate. The result shows that the actuator not only effectively leads to a local rise in near-wall velocity, but also efficiently causes a decrease in the displacement thickness of the boundary layer. Actuator-induced vorticity is generated to intensify the energy exchange between the main flow and the boundary layer, and dynamic energy is thus added directly to the low-energy fluid by the actuator. Although the increase in fluid velocity also brings a rise in dynamic energy loss, the energy added by the actuator can cover this to provide growth in the energy of the boundary layer. The plasma actuator presents a better performance when the free-stream velocity is lower.展开更多
In contrast to Ref.[1]studying MHD processes in a helical channel induced by a vertical rotating electric current layer,in the present report we examine another version with the rotating electric current layer orthogo...In contrast to Ref.[1]studying MHD processes in a helical channel induced by a vertical rotating electric current layer,in the present report we examine another version with the rotating electric current layer orthogonal to the helical channel axis,which leads to an increase in melt velocity with the growing pitch angle α of the helical channel.展开更多
We examine MHD processes arising in melts placed in vessels of circular and rectangular cross-sections under the action of amplitude-and-frequency modulated rotating magnetic field.It is established that besides the m...We examine MHD processes arising in melts placed in vessels of circular and rectangular cross-sections under the action of amplitude-and-frequency modulated rotating magnetic field.It is established that besides the mean turbulent flow,seven oscillations arise in the melt,whose frequency and amplitude depend on modulation parameters.展开更多
The effect of frequency on magnetic flux coupling field were analyzed with traveling-wave electromagnetic stirring system using a coupled model of magnetic induction and fluid dynamics.Simulations were performed to in...The effect of frequency on magnetic flux coupling field were analyzed with traveling-wave electromagnetic stirring system using a coupled model of magnetic induction and fluid dynamics.Simulations were performed to investigate the influences of the frequency on magnetic flux density,electromagnetic body force and flow field.The results showed that the magnetic flux density decreased with increasing frequency.The electromagnetic body force wavy moved along the same direction and increased with increasing the frequency when the traveling magnetic field is applied. The core area of the stirring was in the bottom of the alloy melt.A large circulation in the vertical section of the alloy melt can be produced by the electromagnetic body and the maximum flow rate first increased and then decreased with increasing frequency.展开更多
We examine a convective dissipation-free heat transfer in melts under the action of a stationary component of electromagnetic body force induced by frequency-modulated travelling magnetic field.The influence of MHD pa...We examine a convective dissipation-free heat transfer in melts under the action of a stationary component of electromagnetic body force induced by frequency-modulated travelling magnetic field.The influence of MHD parameters of turbulent flow on the transfer process is studied.展开更多
In this paper, we first develop the far field asymptotic solutions of the second-order scattering waves for the vertical plane problem taking the second-order Stokes waves as the incident waves. The asymptotic solutio...In this paper, we first develop the far field asymptotic solutions of the second-order scattering waves for the vertical plane problem taking the second-order Stokes waves as the incident waves. The asymptotic solutions satisfy the Laplace equation, the sea bed and free surface boundary conditions and are the out-going waves. Then the radiation conditions of the second-order mattering waves are derived by using the asymptotic solutions. By using the two-dimensinal finite clement method with the radiation conditions imposed on the ar- tificial boundaries, the computer program, known as 'NWF2', for determining nonlinear wave forces on large submerged bodies has been written. As a numerical example, nonlinear wave forces on a semi-circu- lar cylinder lying on the sea bed arc presented.展开更多
Under certain conditions, starting from the three-dimensional dynamic equations of elastic shells the author gives the justification of dynamic equations of flexural shells by means of the method of asymptotic analysis.
This paper is devoted to the assessment of ship maneuvering simulation using different propeller models with the focus on a simplified propeller model that represents the action of the propeller by body force and uses...This paper is devoted to the assessment of ship maneuvering simulation using different propeller models with the focus on a simplified propeller model that represents the action of the propeller by body force and uses propeller performance curve to determine propeller loading during ship maneuvering.Simulations are also performed with an actual propeller approach with which the propeller rotation is simulated directly with the Reynolds averaged Navier-Stokes equation(RANSE)solver.Both time accurate simulations using sliding grid and rotating frame approximations have been performed for comparison.The zigzag and turning circle maneuvers in calm water have been simulated for two different ship models,namely the ONR tumblehome(ONRT)test case and the KRISO(Korea Research Institute of Ship and Ocean)Container Ship(KCS)test case.Predicted ship motion is compared with measurement data to assess the accuracy of the numerical prediction using RANSE computations with different propeller models.展开更多
文摘Combining Dual Reciprocity Method （DRM） with Hybrid Boundary Node Method （HBNM）, the Dual Reciprocity Hybrid Boundary Node Method （DRHBNM） is developed for three-dimensional linear elasticity problems with body force. This method can be used to solve the elasticity problems with body force without domain integral, which is inevitable by HBNM. To demonstrate the versatility and the fast convergence of this method, some numerical examples of 3-D elasticity problems with body forces are examined. The computational results show that the present method is effective and can be widely applied in solving practical engineering problems.
文摘This paper deals with a two-dimensional （2D） problem for a transverselyisotropic thick plate having heat sources and body forces. The upper surface of the plate is stress free with the prescribed surface temperature, while the lower surface of the plate rests on a rigid foundation and is thermally insulated. The study is carried out in the context of the generalized thermoelasticity proposed by Green and Naghdi. The governing equations for displacement and temperature fields are obtained in the Laplace-Fourier transform domain by applying the Laplace and Fourier transforms. The inversion of the double transform is done numerically. Numerical inversion of the Laplace transform is done based on the Fourier series expansion. Numerical computations are carried out for magnesium （Mg）, and the results are presented graphically. The results for an isotropic material （Cu） are obtained numerically and presented graphically to be compared with those of a transversely isotropic material （Mg）. The effect of the body forces is also studied.
基金the National Natural Science Foundation of China(Nos.52322603 and 51976005)the Science Center for Gas Turbine Project,China(Nos.P2022-B-II-004-001 and P2023-B-II-001-001)the Fundamental Research Funds for the Central Universities,and Beijing Nova Program,China(Nos.20220484074 and 20230484479).
文摘Accurate prediction of the aerodynamic response of a compressor under inlet distortion is crucial for next-generation civil aircraft,such as Boundary Layer Ingestion(BLI)silent aircraft.Therefore,research on the Body Force(BF)model plays a significant role in achieving this objective.However,distorted inlet airflow can lead to varying operating conditions across different spatial locations of the compressor,which may cause some regions to operate outside the stability boundary.Consequently,the accuracy of BF model simulations might be compromised.To address this issue,this paper proposes a numerical simulation strategy for acquiring the steady axisymmetric three-dimensional flow field of a compressor operating at low mass flow rates,which is known as the Underlying Axisymmetric Pressure Rise Characteristic(UAPRC).The proposed simulation accounts for two different rotor speeds of a transonic compressor and identifies initial positions in the flow field where deterioration occurs based on prior experimental investigations.Moreover,simulation results are incorporated into the BF model to replicate hub instability observed in experiments.Obtained results demonstrate that this strategy provides valid predictions of the UAPRC of the compressor,thereby addressing the limitations associated with the BF model.
文摘After measuring arc electrical current density distribution in gas tungsten arc welding(GTAW) with a probe method, the new expression of body force and model of LD10CS aluminum alloy weld pool are put forward for the first time in GTAW with additional longitudinal magnetic field controlling. The influence of additional longitudinal magnetic field on body force is discussed by electromagnetic principle. This study provides the basis to study fluid flow of the weld pools and arc welding technique with electromagnetic controlling. [
基金the funding support from the Taihang Laboratory,China(No.D2024-1-0201).
文摘As the environmental problems become increasingly serious,distributed electrical propulsion systems with higher aerodynamic efficiency and lower pollution emission have received extensive attention in recent years.The distributed electrical propulsion usually employs the new aero-propulsion integrated configuration.A simulation strategy for internal and external flow coupling based on the combination of lifting line theory and body force method is proposed.The lifting line theory and body force method as source term are embedded into the Navier-Stokes formulation.The lift and drag characteristics of the aero-propulsion coupling configuration are simulated.The results indicate that the coupling configuration has the most obvious lift augmentation at 12°angle of attack,which can provide an 11.11%increase in lift for the airfoil.At 0°angle of attack,the pressure difference on the lip parts provides the thrust component,which results in a lower drag coefficient.Additionally,the failure impact of a ducted fan at the middle or edge on aerodynamics is investigated.For the two failure conditions,the lift of the coupling configuration is decreased significantly by 27.85%and 26.14%respectively,and the lip thrust is decreased by 70.74%and 56.48%respectively.
基金the National Science and Technology Major Project,China(Nos.J2019-Ⅱ-0020-0041 and J2019-Ⅱ-0017-0038)the Science Center for Gas Turbine Project,China(No.P2022-A-Ⅱ-002-001)the National Natural Science Foundation of China(No.52206061).
文摘To numerically study the impact of total temperature distortion on a transonic compressor with reduced computational costs,a Body-Force Model(BFM)is developed.Firstly,the interactions between the distorted flow and the compressor are analyzed using full-annulus Unsteady Reynolds-Averaged Navier-Stokes(URANS)results and the orbit method.It is found that the induced swirl distortion and the mass flux nonuniformity are intensified in the compressor upstream flow field.A correction factor is thus added to the BFM to account for the effect of the induced swirl,which is crucial for the accurate representation of distortion transfer in the intake.Then,steady simulations with large-amplitude 180circumferential total temperature distortion are performed using the developed BFM.It is shown that the distorted compressor map simulated with the BFM matches well with URANS results.The circumferential phase shift of total temperature and the generation of the additional total pressure distortion across the rotor are in line with the time-averaged URANS flow field.The compressor upstream effects on the distorted inflow can also be exactly captured.All above-mentioned results demonstrate the BFM developed in this paper can effectively capture the distorted flow features inside the compressor,and significantly reduce the computational costs by five orders of magnitude compared with URANS.
基金Project supported by the National Natural Science Foundation of China (Grant No :60073044) and the State Key De-velopment Programme for Basic Research of China (Grant No : G1999022207) .
文摘A new finite difference lattice Boltzmann scheme is developed. Because of analyzing the influence of external body force roundly, the correct Navier-Stokes equations with the external body force are recovered, without any additional unphysical terms. And some numerical results are presented. The result which close agreement with analytical data shows the good performance of the model.
基金Project supported by the National Natural Science Foundation of China (Nos. 12232005 and 12072101)the Ningxia Natural Science Foundation of China (No. 2024AAC04004)。
文摘The fracture behavior of superconducting tapes with central and edge oblique cracks subject to electromagnetic forces is investigated. Maxwell's equations and the critical state-Bean model are used to analytically determine the magnetic flux density and electromagnetic force distributions in superconducting tapes containing central and edge oblique cracks. The distributed dislocation technique(DDT) transforms the mixed boundary value problem into a Cauchy singular integral equation, which is then solved by the Gauss-Chebyshev quadrature method to determine the stress intensity factors(SIFs).The model's accuracy is validated by comparing the calculated electromagnetic force distribution for the edge oblique crack and the SIFs for both crack types with the existing results. The findings indicate that the current and electromagnetic forces are significantly affected by the crack length and oblique angle. Specifically, for central oblique cracks, a smaller oblique angle enhances the risk of crack propagation, and a higher initial magnetization intensity poses greater danger under field cooling(FC) excitation. In contrast, for edge oblique cracks, a larger angle increases the likelihood of tape fractures. This study provides important insights into the fracture behavior and mechanical failure mechanisms of superconducting tapes with oblique cracks.
文摘In this paper a nonlinear diffraction theory due to Stoke's 2nd-order wave for computing the wave force on the large body is presented. The radiation condition as r-∞ for 2nd-order scattered potential has been studied in connection with asymptotic solutions. A numerical procedure has been developed for the purpose of calculating the nonlinear wave force on the large body with arbitrary shape.
基金support of National Natural Science Foundation of China (Nos. 51706008 and 51636001)China Postdoctoral Science Foundation (No. 2017M610742)Aeronautics Power Foundation of China (No. 6141B090315)
文摘A coupled supersonic inlet-fan Navier–Stokes simulation method was developed by using COMSOL-CFD code. The flow turning, pressure rise and loss effects across blade rows of the fan and the inlet-fan interactions were taken into account as source terms of the governing equations without a blade geometry by a body force model. In this model, viscous effects in blade passages can also be calculated directly, which include the exchange of momentum between fluids and detailed viscous flow close to walls. NASA Rotor 37 compressor test rig was used to validate the ability of the body force model to estimate the real performance of blade rows. Calculated pressure ratio characteristics and the distribution of the total pressure, total temperature, and swirl angle in the span direction agreed well with experimental and numerical data. It is shown that the body force model is a promising approach for predicting the flow field of the turbomachinery. Then, coupled axisymmetric mixed compression supersonic inlet-fan simulations were conducted at Mach number 2.8 operating conditions. The analysis includes coupled steady-state performance, and effects of the fan on the inlet. The results indicate that the coupled simulation method is capable of simulating behavior of the supersonic inlet-fan system.
文摘The flow over a short intake is characterised by a strong interaction with the fan, that can only be captured when the rotor blades are modelled in the numerical simulations. In this paper, we use a coupled methodology to derive indications about relevant geometric variables affecting the high-incidence operation of an ultra-high bypass ratio turbofan intake with a length-to-diameter ratio of 0.35. By reproducing the effect of the fan through a body force model, we carry out a parametric study of the influence of the contraction ratio and the scarf angle at take-off conditions for a grid of 28 different three-dimensional shapes. The analysis of the selected performance metrics distributions at three angles of attack of 16., 24., and 28. reveals that a contraction ratio higher than 1.20 is needed to avoid separation at high incidence. While for an attached inlet the best performance is found with a moderate scarf angle, in presence of a developed separation the distortion level reduces as the scarf decreases up to negative values. We discuss the correspondence between the distortion indexes and the flow field, highlighting the origin of the detachment for the different geometries, according to the operating condition, and analysing the fan operation in the most distorted case. Finally, we assess the influence of modelling the rotor in the simulations, showing that its suppression effect on the separation at a given incidence depends on the intake geometric features.
文摘The electric-static body force model is obtained by solving Maxwell＇s electromagnetic equations. Based on the electro-static model, numerical modeling of flow around a cylinder with a dielectric barrier discharge （DBD） plasma effect is also presented. The flow streamlines between the numerical simulation and the particle image velocimetry （PIV） experiment are consistent. According to the numerical simulation, DBD plasma can reduce the drag coefficient and change the vortex shedding frequencies of flow around tile cylinder.
基金supported by National Natural Science Foundation of China(No.50976026)the Science Fundamental Research Funds for the Central Universities of China(No.HIT.NSRIF.2013092)
文摘Particle image velocimetry experiments and simulations were conducted in this study to clarify the influence of the DBD plasma actuator on the flow over a flat plate. The result shows that the actuator not only effectively leads to a local rise in near-wall velocity, but also efficiently causes a decrease in the displacement thickness of the boundary layer. Actuator-induced vorticity is generated to intensify the energy exchange between the main flow and the boundary layer, and dynamic energy is thus added directly to the low-energy fluid by the actuator. Although the increase in fluid velocity also brings a rise in dynamic energy loss, the energy added by the actuator can cover this to provide growth in the energy of the boundary layer. The plasma actuator presents a better performance when the free-stream velocity is lower.
基金Item Sponsored by framework of International Scientific Project No.C26/251 "MHD Liquid Metal Stirring and its Effect on the Structure of Solidifying Alloys"and Resaerch Center"Mathematical Models of the Continuous Media" (PermRussian Federation)
文摘In contrast to Ref.[1]studying MHD processes in a helical channel induced by a vertical rotating electric current layer,in the present report we examine another version with the rotating electric current layer orthogonal to the helical channel axis,which leads to an increase in melt velocity with the growing pitch angle α of the helical channel.
文摘We examine MHD processes arising in melts placed in vessels of circular and rectangular cross-sections under the action of amplitude-and-frequency modulated rotating magnetic field.It is established that besides the mean turbulent flow,seven oscillations arise in the melt,whose frequency and amplitude depend on modulation parameters.
基金Item Sponsored by National Natural Science Foundation of China [No.51074091]the Natural Science Foundation of Inner Mongolia Autonomous Region [No.2010MS0107]
文摘The effect of frequency on magnetic flux coupling field were analyzed with traveling-wave electromagnetic stirring system using a coupled model of magnetic induction and fluid dynamics.Simulations were performed to investigate the influences of the frequency on magnetic flux density,electromagnetic body force and flow field.The results showed that the magnetic flux density decreased with increasing frequency.The electromagnetic body force wavy moved along the same direction and increased with increasing the frequency when the traveling magnetic field is applied. The core area of the stirring was in the bottom of the alloy melt.A large circulation in the vertical section of the alloy melt can be produced by the electromagnetic body and the maximum flow rate first increased and then decreased with increasing frequency.
文摘We examine a convective dissipation-free heat transfer in melts under the action of a stationary component of electromagnetic body force induced by frequency-modulated travelling magnetic field.The influence of MHD parameters of turbulent flow on the transfer process is studied.
文摘In this paper, we first develop the far field asymptotic solutions of the second-order scattering waves for the vertical plane problem taking the second-order Stokes waves as the incident waves. The asymptotic solutions satisfy the Laplace equation, the sea bed and free surface boundary conditions and are the out-going waves. Then the radiation conditions of the second-order mattering waves are derived by using the asymptotic solutions. By using the two-dimensinal finite clement method with the radiation conditions imposed on the ar- tificial boundaries, the computer program, known as 'NWF2', for determining nonlinear wave forces on large submerged bodies has been written. As a numerical example, nonlinear wave forces on a semi-circu- lar cylinder lying on the sea bed arc presented.
基金Project supported by the National Natural Science Foundation of China (No.10071024).
文摘Under certain conditions, starting from the three-dimensional dynamic equations of elastic shells the author gives the justification of dynamic equations of flexural shells by means of the method of asymptotic analysis.
基金This work was made possible thanks to granted access to the HPC resources of CINES and IDRIS computing centers under the allocation A0072A01308 made by Grand Equipement National de Calcul Intensif(GENCI).
文摘This paper is devoted to the assessment of ship maneuvering simulation using different propeller models with the focus on a simplified propeller model that represents the action of the propeller by body force and uses propeller performance curve to determine propeller loading during ship maneuvering.Simulations are also performed with an actual propeller approach with which the propeller rotation is simulated directly with the Reynolds averaged Navier-Stokes equation(RANSE)solver.Both time accurate simulations using sliding grid and rotating frame approximations have been performed for comparison.The zigzag and turning circle maneuvers in calm water have been simulated for two different ship models,namely the ONR tumblehome(ONRT)test case and the KRISO(Korea Research Institute of Ship and Ocean)Container Ship(KCS)test case.Predicted ship motion is compared with measurement data to assess the accuracy of the numerical prediction using RANSE computations with different propeller models.
