Implementation and Evaluation of Near Wall Models along with LES

摘要

Numerical simulation of the flow near wall usually needs finer grids and can be too costly. In recent years, flow modeling near the wall using TBLE (Thin Boundary Layer Equation) model is taken into consideration to solve this problem. This wall model is categorized as a wall stress model and shear stresses as its output can be used as boundary condition for LES (Large Eddy Simulation) which solves the main flow. Using fine grid near wall is the most important specification of this model while the main body of the flow can be simulated with much larger grids. Equations used in this model are simplified Navier-Stokes equations established for near wall conditions. Accuracy of this model along with LES is studied in this paper simulating two different cases of the flow in a simple Open Channel and also a flow over an obstacle with no separation. Predicted velocity profiles using TBLE model were compared with laboratory results of Rodi (1986) and Blom (1993). In general, results were found to be acceptable for both cases. Sensitivity of TBLE model to the fineness of the grid was also investigated and results are presented.