抄録
A refined numerical procedure to obtain the turbulent heat transfer and friction factor using the coarse grid nodes of finite difference calculation is proposed in this paper. The correction technique of velocity and temperature gradients at the wall for solving the turbulent momentum and energy equations is studied. The gradients at the wall are corrected by considering the effects of combination of molecular and turbulent diffusivity. Therefore, this procedure requires neither the wall functions, which have been often adopted in numerical calculations fort urbulent flows, nor a grid node adjacent to the wall to be in the viscous sublayer ; it is applicable to solving any turbulent flow. Calculations due to the propesed method are performed for the prediction of turbulent heat transfer in a tube flow, and the results are compared with those obtained using the conventional k-ε model with wall functions. The results in this paper are preferable especially in the region where the turbulence Reynolds number is low. In addition, to adapt the present method for more general flows, the k-ε model of Chieng and Launder in which the molecular diffusion terms in k and ε are not omitted, is used in conjunction with the present procedure.
