Prediction of Turbulent Flow Over L-Shaped Riblet Surfaces with $k-\varepsilon$ Turbulence Models

$k-\varepsilon$ 난류모델에 의한 L-형 리브렛 주위 난류유동 예측

The paper reports the outcome of a numerical study of flow over idealized L-shaped ribleted surfaces with two-equation turbulence models. In the present study, the Launder and Sharma's k-.epsilon. turbulence model (LS model) is basically N employed, but with a little modification of the additional .epsilon.-source term without affecting its level under 2-dimensional straining in which the term has been calibrated. Compared to the original LS model, the present model has predicted greatly improved drag reduction behavior for this geometry. As a drag reduction mechanism, it is found that the skin-friction in the riblet valleys might be sufficient to overcome the skin-friction increase near the riblet tip. The present predicted results are in good agreement with the recent DN S ones by Choi et al. (1993): differences in the mean velocity prof ile and turbulence quantities are found to be limited to the riblet cavity region. It is also found that turbulent kinetic energy and Reynolds shear stress above the riblets are also reduced in drag-reducing configurations.