Abstract
The flow and drag induced by active pitching of plates in the wake of a cylinder of diameter were experimentally studied for various plate lengths as well as pitching frequencies and amplitudes at Reynolds number . Planar particle image velocimetry and a load cell were used to characterize the flow statistics and mean drag of a variety of cylinder-splitter assemblies. Results show the distinctive effect of active pitching on these quantities. In particular, flow recovery was significantly modulated by , , or . Specific pitching settings resulted in a wake with dominant meandering patterns and faster flow recovery. We defined a modified version of the amplitude-based Strouhal number of the system to account for the effect of the cylinder in active pitching. It characterizes the drag coefficient across all the cases studied, and reveals two regions intersecting at a critical value of . Below this value, the remained nearly constant; however, it exhibited a linear increase with increasing past this critical point. Inspection of the integral momentum equation showed the dominant role of velocity fluctuations in modulating past the critical .
2 More- Received 1 July 2019
- Revised 7 October 2019
DOI:https://doi.org/10.1103/PhysRevE.100.063106
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