The concentration and orientation of fiber in a turbulent T-shaped branching channel flow are investi-gated numerically. The Reynolds averaged Navier-Stokes equations together with the Reynolds stress turbulent model ...The concentration and orientation of fiber in a turbulent T-shaped branching channel flow are investi-gated numerically. The Reynolds averaged Navier-Stokes equations together with the Reynolds stress turbulent model are solved for the mean flow field and the turbulent kinetic energy. The fluctuating velocities of the fluid are assumed as a random variable with Gaussian distribution whose variance is related to the turbulent kinetic energy. The slender-body theory is used to simulate the fiber motion based on the known mean and fluctuating velocities of the fluid. The results show that at low Reynolds number, fiber concentration is high in the flow separation regions, and fiber orientation throughout the channel is widely distributed with a slight preference of aligning along the horizontal axis. With increasing of Re, the high concentration region disappears, and fiber orientation becomes ho-mogeneous without any preferred direction. At high Reynolds number, fiber concentration increases gradually along the flow direction. The differences in the distribution of concentration and orientation between different fiber aspect ratio are evident only at low Re. Both Re and fiber aspect ratio have small effect on the variance of orientation angle.展开更多
On the basis of a simple snow-atmosphere-soil transfer (SAST) model previously developed,this paper presents an improved snow-atmosphere-soil transfer (ISAST) model that has a new numerical scheme and an improved meth...On the basis of a simple snow-atmosphere-soil transfer (SAST) model previously developed,this paper presents an improved snow-atmosphere-soil transfer (ISAST) model that has a new numerical scheme and an improved method of layering the snowpack.The new model takes the snow cover temperature and ice content in the snow cover as prognostic variables.This approach,which effectively solves the snow cover temperature distribution when the snow cover is melting or freezing,lessens the iteration time and computation time,which is important for GCM simulation.In this model,the snow cover is divided into three layers (ISAST3) or seven layers (ISAST7).The simulation results obtained using the ISAST7 model agree well with observations in terms of snow depth,snow equivalent water and snow cover lifetime at five Russian sites.The new ISAST model has better simulation capacity for snow cover than the previous SAST model.When the snow cover is deep,the simulation of the ISAST7 model is better than that of the ISAST3 model.Testing shows that our ISAST model is approximately 20% faster than the SAST model.展开更多
基金Supported by the Major Program of the National Natural Science Foundation of China (No.10632070).
文摘The concentration and orientation of fiber in a turbulent T-shaped branching channel flow are investi-gated numerically. The Reynolds averaged Navier-Stokes equations together with the Reynolds stress turbulent model are solved for the mean flow field and the turbulent kinetic energy. The fluctuating velocities of the fluid are assumed as a random variable with Gaussian distribution whose variance is related to the turbulent kinetic energy. The slender-body theory is used to simulate the fiber motion based on the known mean and fluctuating velocities of the fluid. The results show that at low Reynolds number, fiber concentration is high in the flow separation regions, and fiber orientation throughout the channel is widely distributed with a slight preference of aligning along the horizontal axis. With increasing of Re, the high concentration region disappears, and fiber orientation becomes ho-mogeneous without any preferred direction. At high Reynolds number, fiber concentration increases gradually along the flow direction. The differences in the distribution of concentration and orientation between different fiber aspect ratio are evident only at low Re. Both Re and fiber aspect ratio have small effect on the variance of orientation angle.
基金supported by National Natural Science Foundation of China(Grant No. 41030106)National Key Projects on Global Change Studies (Grant No. 2010CB951801)
文摘On the basis of a simple snow-atmosphere-soil transfer (SAST) model previously developed,this paper presents an improved snow-atmosphere-soil transfer (ISAST) model that has a new numerical scheme and an improved method of layering the snowpack.The new model takes the snow cover temperature and ice content in the snow cover as prognostic variables.This approach,which effectively solves the snow cover temperature distribution when the snow cover is melting or freezing,lessens the iteration time and computation time,which is important for GCM simulation.In this model,the snow cover is divided into three layers (ISAST3) or seven layers (ISAST7).The simulation results obtained using the ISAST7 model agree well with observations in terms of snow depth,snow equivalent water and snow cover lifetime at five Russian sites.The new ISAST model has better simulation capacity for snow cover than the previous SAST model.When the snow cover is deep,the simulation of the ISAST7 model is better than that of the ISAST3 model.Testing shows that our ISAST model is approximately 20% faster than the SAST model.
