Physics and Control of Flow Over 3-D Bluff Bodies

Project Sponsor: 
http://www.nsf.gov/
Focus Area: 
Energy Research
Principal Investigator: 
Researchers: 
The shear layer shown with vorticity (left) indicates the spatial locations where the spectra (right) are measured.
Description: 

This projects supports the study of Active Flow Control on bluff bodies including civil engineering structures as well as various slung-load containers. Unsteady aerodynamic loading on bluff bodies arise from pressure fluctuations in the near-wake region due to the Von Kármán (VK) vortex. The dynamics in the wake of the body have been shown to respond to excitation of the smaller Kelvin-Helmholtz (KH) vortex structure which grows within the separated shear layers alongside the body. An efficient Active Flow Control design necessitates thorough understanding of the fundamental physics relating these two vortex systems.

Therefore, fundamental behavior of separated shear layers is the main focus of this work with the intention of understanding its dynamic implications on a two and three dimensional bodies.  Thus far this work has focused on the 2D square prism.  Future experiments will include experiments on 3D bodies.

Schematic depicting the measurement locations of interest relative to the model and the fluid structures which can be identified using PIV

Sample of hot wire time history showing the signature of the Kelvin Helmholtz vortex period (TKH) riding on the top of the flapping shear layer which oscillates at the von Kármán frequency with period (TVK)

Instantaneous images taken at three different Reynolds numbers (Q Criterion on the left, Vorticity on the right). Vortex formation and subsequent interactions depend on the free stream Reynolds number