Theoretical Analysis of Control Mechanisms for Boundary-Layer Separation on Rotorcraft Blades
Abstract
High maneuverability is one of the major goals in rotorcraft design. In practice, this goal is limited by unsteady (dynamic) stall near blade leading edges. Studies of three-dimensional boundary layer separation on a rotating blade are made. For hovering flight, the blade twist and downwash are included in the effective angle of attack. For forward flight, high angles of attack are used to simulate the most severe situation at the retreating blade. Because of the disparate scales of the leading edge radius and the blade span, separation is found to be quasi two-dimensional, and local singular behaviors at separation are very similar to the two-dimensional cases. Most of the results are obtained using an Eulerian approach, but a Lagrangian formulation is used to study the behavior near the separation singularity. Control mechanisms based on suction and blade oscillations are examined. It is found that oscillations, with a tuned frequency and amplitude, can delay separation. Leading edge suction/injection is also effective in delaying separation for particular (optimized) slot locations.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 2007
- Accession Number
- ADA470926
Entities
People
- Philip A. Blythe
Organizations
- Lehigh University