A PRELIMINARY-STUDY ON THE FIXED TRANSITION TECHNIQUE FOR A SHOCK-TUBE TRANSONIC AIRFOIL FLOW

The fixed transition technique, often used in conventional wind tunnel testings, was tried in a shock tube transonic flow with an NACA 0012 airfoil. Tests were performed by placing scotch tapes of 0.06 mm thickness on the surface of the airfoil as the trip strip, and the flow field was observed with schlieren method, and the boundary layer transition was confirmed by the profile of the main shock wave. The hot gas Mach number and Reynolds number based on the chord length were 0.84 and 0.39 million, respectively. It was revealed that the original two dimensional tape did not work properly as a trip strip because relatively strong compression waves were formed at the strip. Various configurations of the strip were tested to weaken the waves produced at the tape position and to get the desirable main shock profile on the surface of the airfoil. From these tests, it was found that the fixed transition technique is applicable to such a shock tube airfoil flow, and the optimum fixed transition for the shock tube airfoil flow could be obtained by placing 12 pieces of the tape of 2.5 mm spanwise, 0.5 mm chordwise and 0.06 mm in thickness at the 5% chord position.