Control of Lift and Drag in Unsteady Flows
Abstract
The response of delta wings with different aspect ratios and a 2-D wing in unsteady free stream was investigated. It was found that the characteristics of the lift forces depend on the existence of leading-edge vortex shedding. For delta wings with attached leading-edge vortex, the time- averaged lift force was found to be independent of reduced frequency since there is no intrinsic vortex convection time scale. With increasing angle of attack or aspect ratio, vortex shedding can occur, and the time required to convect along the chord becomes an intrinsic time scale. The appearance of the intrinsic convection time scale on the delta wing corresponds to increased lift with increasing reduced frequency, just like the 2-D wing. Flow visualizations of vortex breakdown position around the trailing edge does not affect the lift force. For the 2-D wing, the aerodynamic performance in the poststall region shows a maximum at an optimum frequency. Very high lift coefficients exceeding 10 can be observed at this reduced frequency.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1992
- Accession Number
- ADA253146
Entities
People
- Ho Chih-ming
Organizations
- University of Southern California