A-SURF: Acoustically self-resonating surfaces for boundary layer flow control
Abstract
This project aims to investigate the underlying physics of turbulent boundary layer flow-control, using acoustically self-resonating surfaces. The intent is to subtly attenuate features of the boundary layer turbulence that are primarily responsible for the generation of turbulent skin friction. These features include sweep events, which transport relatively higher momentum fluid towards the wall. When the intensity of such sweep events is attenuated, the mean wall-shear stress should decrease. The proposed passive surface-texture consists of arrays of miniature Helmholtz resonators, e.g., matrices of sub-surface cavities with small thru-holes, which absorb the intensity of the sweep events due to the excited self-resonance. How the self-excited (acoustic) resonance couples with the broader band of scales of grazing turbulence is a pending question. One prerequisite aspect of this acoustic pressure-velocity coupling involves the proper tuning of the surface parameters to the scales that are being targeted. Only when correctly scaled, and tested over a large range of (practically-relevant) friction Reynolds numbers Re_tau, we can deduce firm conclusions on the working principle and its potential for flow control. By following the proposed scaling, we will achieve: feasible (millimeter) size resonators for practical flow conditions, a tuning of the self-resonance to the most energetic velocity fluctuations and inferior geometric-disturbances (in comparison to outer-scaled techniques).
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 20, 2023
- Source ID
- FA86552217168
Entities
People
- Woutijn Baars
Organizations
- Air Force Office of Scientific Research
- Delft University of Technology
- United States Air Force