Flow separation and reattachment are widespread in engineering in general, and in aeronautics in particular. One of the issues that concern the researchers over the years is the possibility to control the flow separation zone and the reattachment point location. In the second half of the 20th century, the possibility of replacing rigid walls with wavy surfaces was examined. Results of previous studies indicate that adding a wavy surface can delay the transition of the flow from laminar to turbulent.
The flow over a backward facing step is a fundamental model of flow separation. In this study, the flow over a backward facing step with a wavy surface was examined. The effect of the frequency and amplitude of the wavy surface on the drag force, the flow stability for small disturbances and on the location of the reattachment point were studied numerically. The results show that the viscus drag force is increased. The location of the reattachment point and the stability of the flow are also influenced by the choice of the surface parameters. It was found that the wavy surface amplitude and frequency that improve the flow stability also increase the drag force.
