Computational Study of the Dynamics of the Flow-Field Induced by Vortex Generators

Abstract

Vortex Generators (VGs) are one of the most commonly used passive flow control devices. Recent studies have shown that it is beneficial to use sub-boundary layer vortex generators (SBVGs). The height of these generators varies between 10% - 50% of the boundary layer thickness. However, the reduced height causes the induced vortices to be substantially weaker. Therefore, using SBVG is beneficial only when the regions of flow separation are well defined. To better understand and comprehensively predict the effectiveness of these devices for flow control over a range of operating conditions, two different SBVG profile: rectangular vortex generators (RVGs) and triangular vortex generators (TVGs) are analysed when subjected to a laminar boundary layer. The topics of interest are instantaneous flow, mean flow, far-field acoustic properties and influence of the angle of attack on the VG vane. The results emphasise the unsteady nature of the induced vortices for both the VG profiles. For RVGs, mean flow visualisation indicates the presence of local re-circulation zones in between the vanes with an increase in angle of attack. Additionally, secondary vortices are noted for both the VGs. These secondary vortices significantly influence the properties of the primary vortices thereby, suggesting that, effectively managing the secondary vortices using suitable design changes to VG profile could be one of the possible ways to accomplish better flow control.