Improvement of the Automatic Grid Adaptation for Vortex Dominated Flows Using Advanced Vortex Indicators with the DLR-Tau Code

Abstract

Vortex dominated flows appear in many flow simulations such as wake turbulence of an aircraft or a delta wing at a high angle of attack. For detailed investigations of vortex breakdown, vortex interactions or tracing vortex cores, an automated grid adaptation with suitable vortex indicators is essential. Physical indicators, e.g. the vorticity magnitude or the total pressure loss, are in most cases not sufficient for correctly identifying a vortex core. This paper presents advanced vortex core indicators which properly identify a vortical structure independent of the flow case. These vortex indicators are tested in typical flow applications to determine the right cutoff value which is important for an automated adaptation procedure. A grid refinement for a delta wing testcase in combination with the newly introduced vortex indicators will demonstrate the improvements compared to the standard pressure loss indicator.

Numerical Spoiler Wake Investigations at the Borders of the Flight Envelope

“…The automatic grid adaptation module of the DLR TAU-code 25,26 was applied in order to better resolve the prevailing flow features like shocks and wake vortices. Based on the well-converged solution of the mediumsized spoiler grid, using the Spalart-Allmaras turbulence model, four grid refinement cycles were carried out.…”

Experimental and numerical aspects of simulating unsteady flows around the X-31 configuration

“…These new sensors are the λ 2 criteria and kinematic vortex number, N k criteria, which take into account the rotation and rate-of-strain of the velocity gradient, and the normalized helicity H n , which takes into account the angle between the translational and rotational velocity vectors. The new sensors are currently being evaluated as to their effectiveness in capturing the relevant flow phenomena in a vortex-dominated flow field [8].…”