Scrutinizing the k-epsilon-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., 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 epsilon-equation has to be increased to conform with experimental evidence under adverse pressure gradient conditions. A corresponding modification of the epsilon-equation was employed in the present investigation and resulted in improved predictions. However, for strongly decelerated flows additional tuning of the empirical constants was necessary to obtain satisfactory predictions.