The near surface flow over a dimpled surface with flow injection through it was documented using time-resolved particle image velocimetry. The instantaneous flow structure, time-averaged statistics, and results from snapshot proper orthogonal decomposition were used to examine the coherent structures forming near the dimpled surface. In particular, the modifications made to the flow structures by the addition of flow injection through the surface were studied. It was observed that without flow injection, inclined flow structures with alternating vorticity from neighboring dimples are generated by the dimples and advect downstream. This behavior is coupled with fluid becoming entrained inside the dimples, recirculating and ejecting away from the surface. When flow injection was introduced through the surface, the flow structures became more disorganized, but some of the features of the semi-periodic structures observed without flow injection were preserved. The structures with flow injection appear in multiple wall-normal layers, formed from vortical structures shed from upstream dimples, with a corresponding increase in the size of the advecting structures. As a result of the more complex flow field observed with flow injection, there was an increase in turbulent kinetic energy and Reynolds shear stress, with the Reynolds shear stress representing an increase in vertical transport of momentum by sweeping and ejecting motions that were not present without flow injection.
|Journal||Experiments in Fluids|
|State||Published - Mar 1 2018|
Bibliographical noteFunding Information:
Acknowledgements This research was supported by Kentucky EPS-CoR and NASA Award NNX13AN04A.
© 2018, Springer-Verlag GmbH Germany, part of Springer Nature.
ASJC Scopus subject areas
- Computational Mechanics
- Mechanics of Materials
- Physics and Astronomy (all)
- Fluid Flow and Transfer Processes