Extending the active model split to compressible flows




Pederson, Clark Curtis

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Hybrid RANS/LES models have consistently shown superior accuracy over RANS in predictions of massively separated flows. However, these models have experienced difficulties with modeled stress depletion, smooth-wall separated flow, and shock-separated flows. The Active Model Split (AMS) hybridization was created to address some of the fundamental shortcomings of traditional hybrid RANS/LES models. While previous work considered incompressible flows, this thesis demonstrates how the AMS framework can be extended to address compressible flows. AMS-based hybrid models for the turbulent heat flux and turbulent transport terms in the total energy equation are presented. This compressible hybrid RANS/LES framework is demonstrated on a subsonic channel, a supersonic channel, an axisymmetric transonic bump, and an impinging shock boundary-layer interaction. Some features, such as shock location and separation length, are seen to improve with the AMS framework. The AMS framework is shown to be resistant to modeled stress depletion, though modeling errors in the mean stress can still occur. In general, skin friction is predicted less accurately with the AMS framework than with steady RANS models. Possible explanations for this are given, and model corrections and future lines of research are suggested.


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