Scrutinizing the k-epsilon turbulence model under adverse pressure gradient conditions

The k-epsilon model and a one-equation model have been used to predict adverse pressure gradient boundary layers. While the one-equation model gives generally good results, the k-epsilon model reveals systematic discrepancies, e.g., excessively high skin friction coefficients, for these relatively simple flows. These shortcomings are examined and it is shown by an analytical analysis for the log-law region that the generation term of the epsilon-equation has to be increased to conform with experimental evidence under adverse pressure gradient conditions. A corresponding modification to the epsilon-equation emphasizing the generation rate due to deceleration was employed in the present investigation and resulted in improved predictions for both moderately and strongly decelerated flows.