Método de interação viscosa/não-viscosa para redução do domínio computacional em problemas de aerodinâmica

Abstract

Since CFD simulations for external flow problems may cause high computational costs, the present work presents a viscous/inviscid interaction method that allows to simulate the viscous flow in a reduced computational domain, which encompasses the rotational flow region (also called viscous subdomain). To this end, an interactive methodology is proposed, which consists of: calculate the potential flow outside the rotational region, impose the velocity of potential flow as a boundary condition at the boundary of the viscous subdomain, calculate the transpiration velocity to correct the potential flow, recalculate the field of potential flow velocities outside the rotational region, and update boundary conditions in the viscous subdomain. To determine the transpiration velocity, the velocity decomposition approach was used, which has been explored to develop methods of viscous/inviscid interaction. In this approach, to calculate the transpiration, it is necessary to first determine a boundary where the vorticity is negligible (called the rotational boundary). Determining the rotational boundary can be a complex task. Thus, two proposals were made to address this issue: the use of an auxiliary surface to facilitate the determination of rotational boundary (and to serve as a control surface for the potential flow), and to use of alternative criteria to evaluate the negligible vorticity. Calculations were performed in the viscous subdomain for two-dimensional, incompressible, steady, laminar or turbulent flows problems, on the profile NACA 0012 , bluff bodies and multiple bodies. The use of the proposed methodology allowed to reduce the computational costs, and the results of the aerodynamic coefficients and of the viscous flow fields obtained in the reduced domain, in general, were satisfactory for the engineering levels.