Titel: A PIV Study of Separated Flow around a 2-D Airfoil at High Angles of Attack in a Low Speed Wind Tunnel, FFA TN 1999-52
Författare: Richard Holm & Jonas Gustavsson
Utgivare: Flygtekniska Försöksanstalten, FFA, Vindforsk
Årtal: 1999
Ämnesord: Mekanik och aerodynamik
Sökord/keywords: CFD, PIV
Rapport (Pdf)
Sammanfattning/Abstract: Wind tunnel tests were carried out in order to acquire experimental data for validation of numerical results from Navier-Stokes calculations
(CFD-simulations) on airfoils at high angles of attack. The tests were performed on the 21% thick FFA-W3-211 airfoil geometry, 2-dimensional wind tunnel model with 0.45m chord and 2m span. The purpose of the study was to examine the flow field around the airfoil at 8° and 15° angle of attack, in particular to determine the position of the separation and the recirculating region. The wind tunnel tests were carried out at Re=1.25.million. The used measurement techniques were pressure measurement, oil flow visualisation and PIV (Particle Image Velocimetry).
The boundary layer transition was trigged at a fixed position (x/c=0.026 on the suction side and x/c=0.312 on the pressure side) by means of an adhesive zigzag tape. The uncertainties regarding the position of transition was thereby reduced.
Based on the velocity vector field obtained by the PIV data the velocity profile, boundary layer quantities and the back-flow coefficient were derived. The back-flow coefficient was then used as a criterion for separation.
The conclusions of the study were:
· The flow field was determined by PIV and available for comparison
with CFD-results.
· Based on the velocity field the separation position, the velocity
profile at different chordwise positions and boundary layer quantities
were derived.
· The separation position, for 15° angle of attack, was determined in
the PIV measurements to x/c=0.39±0.03 and in the pressure
measurements to x/c=0.40±0.05 and somewhat subjectively in the oil
flow to x/c»0.42.
The data are available on file format for comparison with CFD results.