On the origin of the drag force on dimpled spheres
| Autor: | Elias Balaras, Kyle D. Squires, Nikolaos Beratlis |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
Physics
Drag coefficient Mechanical Engineering Flow (psychology) Reynolds number 02 engineering and technology Mechanics Condensed Matter Physics 01 natural sciences 010305 fluids & plasmas Physics::Fluid Dynamics symbols.namesake Flow separation 020303 mechanical engineering & transports 0203 mechanical engineering Mechanics of Materials Drag Dimple Drag crisis 0103 physical sciences symbols SPHERES |
| Zdroj: | Journal of Fluid Mechanics. 879:147-167 |
| ISSN: | 1469-7645 0022-1120 |
| Popis: | It is well established that dimples accelerate the drag crisis on a sphere. The result of the early drag crisis is a reduction of the drag coefficient by more than a factor of two when compared to a smooth sphere at the same Reynolds number. However, when the drag coefficients for smooth and dimpled spheres in the post-critical regime are compared, the latter is higher by a factor of two to three. To understand the origin of this behaviour, we conducted direct numerical simulations of the flow around a dimpled sphere, which is similar to commercially available golf balls, in the post-critical regime. By comparing the results to those for a smooth sphere, it is found that dimples, although effective in accelerating the drag crisis, impose a local drag penalty, which contributes significantly to the overall drag force. This finding challenges the broadly accepted view that dimples only indirectly affect the drag force on a sphere by energizing the near-wall flow and delaying global separation. |
| Databáze: | OpenAIRE |
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