The Onset of Dynamic Stall: Understanding Flowfield Unsteadiness to Enable Closed-Loop Control
Abstract
The current study was conducted in order to characterize the quantitative spatiotemporal scales associated with the dynamic stall flow field across a transitional-Reynolds number regime. Across these higher Reynolds numbers, a series of flow field interactions were observed to produce a broad distribution of scales not observed in the canonical dynamic stall process at lower Reynolds numbers from the literature. From this study, unsteady flow oscillations associated with a laminar separation bubble were identified. These oscillations emerged prior to the inception of the dynamic stall process, and were observed to follow a Strouhal number scaling of 1.2, when the separation bubble height was used as the characteristic length scale. Further study of the off-body velocity field revealed variations in the developmental morphology of the dynamic stall vortex with changing Reynolds number. An Empirical Mode Decomposition method was coupled to a Hilbert spectral analysis method to provide a quantitative characterization of the temporal scales that emerge during unsteady separation and dynamic stall vortex formation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 19, 2019
- Accession Number
- AD1085947
Entities
People
- Phillip J. Ansell