The validation of RANS models for motion-, externally- and instability-induced transient flows based on wind tunnel experiments represents the second major focus within unsteady aerodynamics at the Institute of Aeroelasticity.
The RANS equations come with the difficulty of modelling the Reynolds Stress Tensor based on so-called turbulence models. A number of turbulence models produce some significant differences in the steady solutions themselves, in particular for transonic flow with pronounced shock-boundary layer interaction. In typical cases, unsteady solutions will ‘inherit’ and even exacerbate all deviations already present in the underlying steady solution. Moreover, the majority of turbulence models available today are essentially unable to predict the transition point between laminar and turbulent boundary layers. It therefore follows that they need to be supplemented by an additional transition model. However, the resulting uncertainties exceed – in some cases substantially – the range of variation that was already introduced by the turbulence modelling. Hence, experimental validation through wind tunnel measurements is necessary.
For this purpose, the Institute of Aeroelasticity conducts unsteady wind tunnel experiments in the neighbouring Transonic Wind Tunnel in Göttingen, operated by German-Dutch Wind Tunnels (DNW-TWG).
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