Scrutinizing the k-ε Turbulence Model Under Adverse Pressure Gradient Conditions

The k-ε 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-ε model reveals systematic discrepancies, e.g. too 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 ε-equation has to be increased to conform with experimental evidence under adverse pressure gradient conditions. A corresponding modification to the ε-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.