Direct Numerical Simulation of TS-Waves Behind a Generic Step of a laminar Profile in the DNW-NWB wind tunnel

Kurzfassung

The aim of this work is the DNS of local instabilities behind the step of a laminar~airfoil. As a reference-configuration the laminar~airfoil of the "ProWinGS" Project was chosen, as investigated in the DNW-NWB wind~tunnel. The character of the dominating Tollmien-Schlichting (TS) waves on this profile allows 2D simulations of the flow-field by using a well-validated high-order numerical approach (see \cite{Backhaus_2014}), which will be sufficient for a detailed simulation of transitional modes in the region of interest. All calculations were carried out on the original airfoil-geometry by using an entirely meshed step-geometry of the wind~tunnel model. An extraction of the critical area allowed efficient time-accurate simulations of the instabilities near the step. For the extracted boundary-layer, unsteady perturbations were added at inflow, which resemble TS-modes in the step-region. Determining growth rates of these modes allow comparison with LST and the prediction of the laminar-turbulent transition. The middle part of the profile~nose in the open test-section of the DNW-NWB contains an adjustable inset to allow settings of different forward and backward facing steps.