Abstract

The present work models the spatial decay of freestream turbulence using three different commercial Computational Fluid Dynamics (CFD) codes: Fluent, STAR-CCM+, and CFX. The two-equation Shear-Stress transport k-? (SST-k-?) steady RANS model was used, within each of these three different commercial codes, and the modelling variations were analyzed. Comparison of the results from the SST-k-? model with experiments and large eddy simulation (LES) (carried out using STAR-CCM+) were also made which reveal that all the commercial CFD codes demonstrate either a higher or slower rate of spatial turbulent kinetic energy (TKE) decay. Attempts were then made to unify the resultant modelling approach between these three CFD tools, by careful manipulation of the inlet boundary conditions and subsequent fine-tuning of the SST-k-? model constant ( ). The results obtained not only displayed uniformity among the three CFD codes but also demonstrated a much better agreement to the experiments and the LES results. Thereafter, the optimized model coefficient ( ) was integrated with the three-equation k-kl-? transition model to examine its applicability in modelling a turbulent boundary layer flow over a flat plate with low incoming turbulence. The results showed good agreement with the theoretical boundary layer correlations, with correct prediction of the transition location. The findings from the present study can be used as a suitable modelling method to accurately model the effects of freestream turbulence on bluff-body and boundary layer flows.

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