Analysis of Unsteady Flow Around Airfoil of a HAWT by Vortex Method

Abstract

Vortex methods have features such as relatively simple algorithm, no grid-generation in flow field and lagrangian scheme which traces each vortex element concentrated in a tiny region. It is considered that the vortex methods are effective tools for the analysis of three-dimensional, incompressible and unsteady outer flow such as flow around wind turbines. Recently, vortex methods are employed as engineering tools for three-dimensional unsteady flow. In a flow simulation by vortex methods, accuracy of simulation depends chiefly on the vortex creation model on the wall and the viscous diffusion effects. However, it seems that the deterministic model to introduce the vortex element created on the wall into flow field has not yet been accomplished. In this paper, an introduction model of vortex elements from the wall into flow field is proposed. This model is based on the analogy of the consideration of boundary-layer. In this model, intensity of vortex elements created on the wall is determined by applying both no-through and no-slip boundary conditions and the diffusion height of each element created on the wall is determined dynamically. To investigate the applicability of the model, proposed method is applied to flow around impulsively started airfoil section.