Sharif Digital Repository

We numerically solve the Navier-Stokes equations to study the rarefied gas flow in short micro- and nanoscale channels. The inlet boundary conditions play a critical role in the structure of flow in short channels. Contrary to the classical inlet boundary conditions, which apply uniform velocity and temperature profiles right at the real channel inlet, we apply the same inlet boundary conditions, but at a fictitious position far upstream of the real channel inlet. A constant wall temperature incorporated with suitable temperature jump is applied at the channel walls. Our solutions for both the classical and extended inlet boundary conditions are compared with the results of other available... 

We numerically solve the Navier-Stokes equations to study the rarefied gas flow in short micro-and nanoscale channels. The inlet boundary conditions play a critical role in the structure of flow in short channels. Contrary to the classical inlet boundary conditions, which apply uniform velocity and temperature profiles right at the real channel inlet, we apply the same inlet boundary conditions, but at a fictitious position far upstream of the real channel inlet. A constant wall temperature incorporated with suitable temperature jump is applied at the channel walls. Our solutions for both the classical and extended inlet boundary conditions are compared with the results of other available... 

Experiments were conducted to study various kinds of Shock wave/Boundary Layer Interaction (SBLI) in an axisymmetric mixed-compression inlet. Experimental findings were compared and verified by numerical solutions where possible. Different types of SBLI relevant to the mixed-compression inlets are classified. Interactions of normal shock wave/boundary-layer at subcritical condition and in buzz condition are investigated using Schlieren and shadowgraph flow visualization as well as unsteady pressure recordings. The data is compared with the CFD predictions. Interactions of cowl lip reflected oblique shock and the terminal normal shock with the spike boundary-layer at both critical and... 

Overall turbine analysis requires large CPU time and computer memory, even in the present days. As a result, choosing an appropriate computational domain accompanied by a suitable boundary condition can dramatically reduce the time cost of computations. This work compares different geometries for numerical investigation of the 3D flow in the runner of a Francis turbine, and presents an optimum geometry with least computational effort and desirable numerical accuracy. The numerical results are validated with a GAMM Francis Turbine runner, which was used as a test case (GAMM workshop on 3D computation of incompressible internal flows, 1989) in which the geometry and detailed best efficiency...