Flow and noise predictions for a tandem cylinder configuration using novel hybrid RANS/LES approaches

Abstract

The performance of several novel hybrid RANS/LES methodologies for accurate flow and noise predictions of the NASA Tandem Cylinder Experiment are investigated. Simulations are performed using three different hybrid RANS/LES methodologies which employ different techniques to transform the baseline RANS model into a turbulence resolving subgrid scale model. The approaches investigated are the Scale-Adaptive-Simulation which computes the subgrid dissipation-rate from a transport equation that is sensitive to the v. Karman length scale, the IDDES approach and a modified Flow-Simulation-Methodology (FSM) which both rely on replacing the modeled turbulent length scale with a measure of the local grid spacing. Since we expect that the predictions in the RANS and LES region depend on the capabilities of the baseline RANS model, the hybrid RANS/LES approaches used in this study are based on an Explicit-Algebraic-Stress Model. These models are assessed and compared with formulations based on a traditional two-equation model. The simulations are performed with the open-source finite volume code OpenFOAM and acoustic predictions are obtained using an acoustic analogy based on Curle's theory. The IDDES and FSM approaches were found to predict the hydrodynamic field in very good agreement with reference data but showed some deficiencies in capturing the higher harmonics in the acoustic spectra and broadband noise levels at high Strouhal numbers. The SAS appraoches lack in accuracy for prediciting the hydrodynamic field but resolve the higher harmonics in the acoustic spectra.