Thermally-stratified shear turbulent channel flow with temperatureoscillation on the bottom wall of the channel was investigated with the Large Eddy Simulation (LES)approach coupled with dynamic Sub-Grid-Scale (SGS) m...Thermally-stratified shear turbulent channel flow with temperatureoscillation on the bottom wall of the channel was investigated with the Large Eddy Simulation (LES)approach coupled with dynamic Sub-Grid-Scale (SGS) models. The effect of temperature oscillation onthe turbulent channel flow behavior was examined. The phase-averaged velocities and temperature, andflow structures at different Richardson numbers and periods of the oscillation was analyzed.展开更多
The objective of this study is to deal with unsteady force acting on a pitching foil in shear flow and to study the relation of the force characteristics with vortex shedding near the foil. The two dimensional incomp...The objective of this study is to deal with unsteady force acting on a pitching foil in shear flow and to study the relation of the force characteristics with vortex shedding near the foil. The two dimensional incompressible Navier Stokes equations in the vorticity and stream function formulation were solved with the fourth order essentially compact finite difference schemes for the space derivatives and a fourth order Runge Kutta scheme for the time advancement. The force characteristics and vortex shedding of the pitching foil in shear flows were investigated. The effects of some typical factors, including the incoming flow shear, the oscillating frequency and amplitude, on the vortex shedding and force behavior were analyzed and discussed.展开更多
Fully developed vertical turbulent channel flow with particle transport wasinvestigated by use of Large Eddy Simulation (LES) approach coupled with dynamic the Sub-Grid Scale(SGS) model. It was assumed that the motion...Fully developed vertical turbulent channel flow with particle transport wasinvestigated by use of Large Eddy Simulation (LES) approach coupled with dynamic the Sub-Grid Scale(SGS) model. It was assumed that the motion of each particle is followed in a Lagrangian frame ofreference driven by the forces exerted by fluid motion and gravity under the condition of one-waycoupling. The goal of this study is to investigate the effectiveness of the LES technique forpredicting particle transport in turbulent flow and the behavior of particle-laden turbulent channelflow for three kinds of particles at different Stokes numbers. To depict the behavior ofparticle-laden turbulent channel flow, statistical quantities including particle fluctuation andfluid-particle velocity correlation, and visualization of the particle number density field wereanalyzed.展开更多
Pulsating turbulent open channel flow has been investigated by the use ofLarge Eddy Simulation (LES) tech-nique coupled with dynamic Sub-Grid-Scale (SGS) model for turbulentSGS stress to closure the governing equation...Pulsating turbulent open channel flow has been investigated by the use ofLarge Eddy Simulation (LES) tech-nique coupled with dynamic Sub-Grid-Scale (SGS) model for turbulentSGS stress to closure the governing equations. Three-dimensional filtered Navier-Stokes equationsare numerically solved by a fractional — step method. The objective of this study is to deal withthe behavior of the pulsating turbulent open channel flow and to examine the reliability of the LESapproach for predicting the pulsating turbulent flow. In this study, the Reynolds number (Re_τ) ischosen as 180 based on the friction velocity and the channel depth. The frequency of the drivingpressure gradient for the pulsating turbulent flow ranges low, medium and high value. Statisticalturbulence quantities as well as the flow structures are analyzed.展开更多
The transition process of intermittent flow in a longitudinal section of Bingham fluid from initial distribu-tion to fully developed state was numerically investigated in this paper. The influences of slope ,J dimensi...The transition process of intermittent flow in a longitudinal section of Bingham fluid from initial distribu-tion to fully developed state was numerically investigated in this paper. The influences of slope ,J dimensionless runoff Q* and viscosity m*0on the dimensionless surge speed U* were also presented in a wide range of parameters. By one typical example, the intermittent flow possessed wave char-acteristics and showed a supercritical flow conformation for a fully developed flow. The distributions of gravity and bed drag along the flow path and the velocity distribution of flow field were also analyzed.展开更多
This study presents the numerical results for the three dimensional natural gas air mixing in a rectangular subsonic channel under the standard datum state. The lower and upper decomposition method was employed to o...This study presents the numerical results for the three dimensional natural gas air mixing in a rectangular subsonic channel under the standard datum state. The lower and upper decomposition method was employed to obtain the solutions of the full Navier Stokes equations capable of describing compressible fluid mixing. Grid was generated by the area orthogonal technique. The results indicate that three dimensional mixing between Natural Gas (NG) and air has more complicated compressible waves around the injection nozzle. The presence of injection with large speed can suppress the boundary separation happened occurring at the top wall due to the channel expansion, but makes the near wake flow more complicated. The mixing region can be widened by increasing the injection speed. The recurrence of the vortex structure and the coherent structure can be found from the full Navier Stokes simulation. It can be concluded that the increase in the injection velocity can improve the effectiveness of mixing of NG and air in the near wake of the injectors.展开更多
A numerical analysis of non-Newtonian fluid flow in non-planar artery withbifurcation was performed by using a finite element method to solve the three-dimensionalNavier-Stokes equations coupled with the non-Newtonian...A numerical analysis of non-Newtonian fluid flow in non-planar artery withbifurcation was performed by using a finite element method to solve the three-dimensionalNavier-Stokes equations coupled with the non-Newtonian constitutive models, including Carreau, Crossand Bingham models. The objective of this study is to investigate the effects of . thenon-Newtonian properties of blood as well as curvature and out-of-plane geometry in the non-planardaughter vessels on the velocity distribution and wall shear stress. The results of this studysupport the view that the non-planarity of blood vessels and the non-Newtonian properties of bloodare of important in hemodynamics and play a significant role in vascular biology andpathophysiology.展开更多
文摘Thermally-stratified shear turbulent channel flow with temperatureoscillation on the bottom wall of the channel was investigated with the Large Eddy Simulation (LES)approach coupled with dynamic Sub-Grid-Scale (SGS) models. The effect of temperature oscillation onthe turbulent channel flow behavior was examined. The phase-averaged velocities and temperature, andflow structures at different Richardson numbers and periods of the oscillation was analyzed.
基金This work was supported by the National Natural Science Foundation of China (Grant Nos: 10332040 10125210+3 种基金10302028) the Innovation Project of the Chinese Academy of Sciences (Grant Nos: KJCX SW L04 KJCX2 SW L2) and the Programme of Hundred Talents of the Chinese Academy of Sciences.
文摘The objective of this study is to deal with unsteady force acting on a pitching foil in shear flow and to study the relation of the force characteristics with vortex shedding near the foil. The two dimensional incompressible Navier Stokes equations in the vorticity and stream function formulation were solved with the fourth order essentially compact finite difference schemes for the space derivatives and a fourth order Runge Kutta scheme for the time advancement. The force characteristics and vortex shedding of the pitching foil in shear flows were investigated. The effects of some typical factors, including the incoming flow shear, the oscillating frequency and amplitude, on the vortex shedding and force behavior were analyzed and discussed.
文摘Fully developed vertical turbulent channel flow with particle transport wasinvestigated by use of Large Eddy Simulation (LES) approach coupled with dynamic the Sub-Grid Scale(SGS) model. It was assumed that the motion of each particle is followed in a Lagrangian frame ofreference driven by the forces exerted by fluid motion and gravity under the condition of one-waycoupling. The goal of this study is to investigate the effectiveness of the LES technique forpredicting particle transport in turbulent flow and the behavior of particle-laden turbulent channelflow for three kinds of particles at different Stokes numbers. To depict the behavior ofparticle-laden turbulent channel flow, statistical quantities including particle fluctuation andfluid-particle velocity correlation, and visualization of the particle number density field wereanalyzed.
文摘Pulsating turbulent open channel flow has been investigated by the use ofLarge Eddy Simulation (LES) tech-nique coupled with dynamic Sub-Grid-Scale (SGS) model for turbulentSGS stress to closure the governing equations. Three-dimensional filtered Navier-Stokes equationsare numerically solved by a fractional — step method. The objective of this study is to deal withthe behavior of the pulsating turbulent open channel flow and to examine the reliability of the LESapproach for predicting the pulsating turbulent flow. In this study, the Reynolds number (Re_τ) ischosen as 180 based on the friction velocity and the channel depth. The frequency of the drivingpressure gradient for the pulsating turbulent flow ranges low, medium and high value. Statisticalturbulence quantities as well as the flow structures are analyzed.
基金supported by Special Project of the Fundamenta1 Research on Landslide and Debris Flows of the Chinese Academy of Sciencesthe National Natural Science Foundation of China(Grant No.49771003).
文摘The transition process of intermittent flow in a longitudinal section of Bingham fluid from initial distribu-tion to fully developed state was numerically investigated in this paper. The influences of slope ,J dimensionless runoff Q* and viscosity m*0on the dimensionless surge speed U* were also presented in a wide range of parameters. By one typical example, the intermittent flow possessed wave char-acteristics and showed a supercritical flow conformation for a fully developed flow. The distributions of gravity and bed drag along the flow path and the velocity distribution of flow field were also analyzed.
文摘This study presents the numerical results for the three dimensional natural gas air mixing in a rectangular subsonic channel under the standard datum state. The lower and upper decomposition method was employed to obtain the solutions of the full Navier Stokes equations capable of describing compressible fluid mixing. Grid was generated by the area orthogonal technique. The results indicate that three dimensional mixing between Natural Gas (NG) and air has more complicated compressible waves around the injection nozzle. The presence of injection with large speed can suppress the boundary separation happened occurring at the top wall due to the channel expansion, but makes the near wake flow more complicated. The mixing region can be widened by increasing the injection speed. The recurrence of the vortex structure and the coherent structure can be found from the full Navier Stokes simulation. It can be concluded that the increase in the injection velocity can improve the effectiveness of mixing of NG and air in the near wake of the injectors.
文摘A numerical analysis of non-Newtonian fluid flow in non-planar artery withbifurcation was performed by using a finite element method to solve the three-dimensionalNavier-Stokes equations coupled with the non-Newtonian constitutive models, including Carreau, Crossand Bingham models. The objective of this study is to investigate the effects of . thenon-Newtonian properties of blood as well as curvature and out-of-plane geometry in the non-planardaughter vessels on the velocity distribution and wall shear stress. The results of this studysupport the view that the non-planarity of blood vessels and the non-Newtonian properties of bloodare of important in hemodynamics and play a significant role in vascular biology andpathophysiology.
