Thorough analysis of vortical structures in the flow around a yawed bluff body

Abstract

In the present study numerical investigations are used as a complementary approach to analyse large coherent structures in the flow around a bluff-body under cross-wind. The results from the numerical simulation are validated through wind-tunnel experiments and used to analyse unresolved observations from these experimental investigations. This underlines the duality of these two approaches in the analysis of the aerodynamics of a bluff-body. Vortical structures in a three-dimensional, asymmetric and turbulent wake are detected through the use of different vortex detection schemes (vorticity, Q, λ₂ and Γ₃), permitting to isolate flow structures. The vortex properties of two main lateral vortices are described and discussed on the basis of envelopes detected by the λ₂ and the Γ₃ criterion. Although the flow is highly three-dimensional and complex, the vortex properties are quite simple and show mechanisms like vortex stretching and bursting. These two criteria lead qualitatively to the same results; quantitative differences are due to the envelope diameter and are therefore observed only on integral flow quantities.

Keywords:

• bluff-body aerodynamics
• cross-wind
• vortex detection
• vortex analysis