CFD Investigation of Effect of Depth to Diameter Ratio on Dimple Flow Dynamics

摘要

This study aimed to further the understanding of laminar flow through a dimple with the goal of mitigating flow separation. Dimples of various depth to diameter ratios (0.05, 0.15) were examined for three different dimple diameters and chordwise locations, corresponding to diameter based (ReD) and chordwise location based (Rex) Reynolds number combinations of ReD 20500/Rex 5000, ReD 20500 Rex 77000, and ReD 9000 Rex 21000. For the last combination, a dimple of depth to diameter ratio of 0.25 was also examined. The dimples were placed in a flat plate located in a diverging channel causing an adverse pressure gradient encouraging flow separation near the dimple location. The flow was modeled in the commercial CFD solver Fluent. Results indicate that dimple depth to diameter ratio has a significant effect on the structure of dimple flow. The shallowest dimples showed little change to the overall flow in the channel. Deeper dimples contained dynamic vortical flow structures with behavior varying between each dimple studied. This dynamic vortex activity was observed to be linked with variances in downstream flow. The 0.15 depth to diameter ratio dimples showed behavior very similar to 0.10 ratio dimples investigated elsewhere. The 0.25 dimple show flow different in nature than 0.15 dimples for the same ReD and Rex; the differences were not as stark as those between 0.05 and 0.15 dimples. In light of this and other studies, dimple flow behavior is found to depend on a combination of parameters that eludes direct quantitative parameterization. However, the conclusion is drawn that the most effective dimple will be just deep enough to develop dynamic vortical activity and vortex shedding.