Anisotropy analysis of vortex breakdown states via direct numerical simulation

We investigate bubble-type and conical vortex breakdown through direct numerical simulation. Notably, we analyze the anisotropic features of the Reynolds stress and dissipation rate tensors, showing that the latter exhibits less significant anisotropy. Still, high anisotropy is envisaged around the stagnation point. Hence, we test a set of algebraic anisotropic dissipation tensor models for second-moment closure approaches, and we find out that blended formulations governed by the turbulent Reynolds number can identify the most anisotropic dissipation regions. On the contrary, models relating the dissipation tensor to large-scale anisotropies show worse predictive capability, proving that small-scale anisotropies descend from mean flow properties instead.