What is it about?
The verification and validation (V&V) of multi-fidelity turbulence models is crucial for the efficient and reliable industrial application of computational fluid dynamics (CFD). This study aims to evaluate the performance of detached eddy simulation (DES) modeling approaches embedded with various unsteady Reynolds Averaged Navier-Stokes (URANS) models in simulating the turbulent flow fields over a steep-sloped hill. And the highfidelity numerical methodology based on the DES model was proposed and analyzed in the context of URANS modes, mesh resolution and sampling duration. In comparison with the experimental data, the shear stress transport (SST) k-ω based DDES (Delayed Detached eddy simulation) turbulence model (DDES SST k-ω) could better predict the profiles of mean velocity and turbulence fluctuation, while the Spalart-Allmaras (S-A) based DES and DDES turbulence models show its stronger capability to reproduce the spectral characteristics. Additionally, in contrast to DES S-A and DDES S-A, a larger time-averaged separation bubble was predicted by DES SST k-ω and DDES SST k-ω. Moreover, the instantaneous flow patterns such as the formation and evolution of turbulent eddies in the hill wake could be reasonably reproduced by DES S-A and DDES S-A. Furthermore, the numerical results obtained from DES models were sensitive to URANS modes and vertical mesh resolution but trivially affected by the increase in sampling time after reaching the statistical convergence.
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Why is it important?
The findings are expected to improve our understanding of the applicability of DES models to predict turbulent flows over hilly terrain. Additionally, this study confirms that DES models can be applied to realistically reproduce the turbulent flow field over simplified hilly terrain while requiring less computational resources than a pure LES model.
Perspectives
Since the turbulent flow over real complex terrain is comprehensively affected by topographical features (hill shape, hill slope and surface roughness) and surrounding environmental conditions (oncoming flow characteristics), it might be necessary to further examine the performance of DES models for prediction of turbulent flow field over real complex terrain. Moreover, some discrepancies of the predicted unsteady flow patterns can be observed from different DES models, probably caused by the switching between the LES model and the URANS model. This may also be worthy of further study.
Dr. Tong Zhou
The University of Tokyo
Read the Original
This page is a summary of: Detached eddy simulation of turbulent flow fields over steep hilly terrain, Journal of Wind Engineering and Industrial Aerodynamics, February 2022, Elsevier,
DOI: 10.1016/j.jweia.2022.104906.
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