Embedded LDV Measurements in the Boundary Layer of Moving Walls
Abstract
Smoke visualization and embedded laser velocimeter operating in the backscatter mode were used to survey the flow about wings oscillating through stall in the Luminy wind tunnels S1L and S2L. The experiments were carried out about rectangular wings with an NACA 0012 airfoil section at nominal Reynolds numbers R(natural log)=1O(exp 5), 2lO(exp 5), and 10(exp 6). During the oscillation, the wing angle of attack was varied around mean values alpha omicron deg=6; 15; and 21; through an amplitude delta alpha=plus or minus 6 deg, and a reduced frequency k=0-.188. Pictures and movies realized using the laser sheet technique have shown that the features of dynamic stall are independent of Reynolds numbers, at least in the present experiments (10(exp 5) less than or equal to R(natural log) less than or equal to 10(exp 6)). Effects of upstroke and downstroke on separation and reattachment of boundary layer are clearly shown as well as deviation from steady behavior analyzed at the same angle of attack for fixed and oscillating airfoil. The measurements of two orthogonal components of instantaneous velocity through the boundary layer along a normal to the surface of the wing have shown that the embedded laser velocimeter is well suited to characterize qualitatively and quantitatively the structure of the boundary layer (laminar, transition, turbulent) as well as strong separation with leading edge bubble involved during dynamic. These results constitute a useful data base for future computational unsteady boundary layer.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 2000
- Accession Number
- ADA389237
Entities
People
- Christian Maresca
- Daniel Favier
- Eric Berton