Manipulation of Airfoil Response in an Unsteady Stream.
Abstract
Experiments were conducted to investigate the mechanism responsible for vortex breakdown over delta - wing. By varying the free stream velocity, unsteady vortex breakdown occurs over the wing due to the alteration of the balance between leading-edge vorticity production and convection. This allows the study of vortex breakdown in both the spatial and temporal domain. It was found that parameters such as swirl angle and circulation do not correlate well with breakdown when the flow is unsteady. However, vortex breakdown seemed to follow the positive feedback mechanism proposed by Brown and Lopez. When breakdown occurs, there is a redistribution of vorticity in the vortex subcore, where the vorticity vector changes from an essentially axial direction to a generally tangential direction. Further, the helix angle for the velocity exceeds that of the vorticity globally in the vortex subcore only in the instant just before breakdown. Finally, it was found that through breakdown, global quantities such as circulation and flow rate varies in phase as the upstream vorticity and velocity changes with time. This implies that the breakdown process is essentially an inviscid mechanism.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 31, 1996
- Accession Number
- ADA311791
Entities
People
- Chih-ming Ho
Organizations
- University of California, Los Angeles