Session MN - Experimental Techniques III.
ORAL session, Tuesday morning, November 26
Obelisk A, Wyndham Anatole Hotel
A system for measuring the instantaneous global pressure distribution has been developed. The technique is based on measuring the material acceleration of the flow using a PIV based method and, if necessary, the pressure at a reference point. Two 2Kx2K CCD cameras and perpendicularly polarized Nd:Yag lasers are used for recording four exposures, with images 1 and 3 recorded by one camera and images 2 and 4 by the other. During analysis we cross-correlate images 1 and 3 with image 2. The sample areas are shifted according to the local velocity to accommodate the material displacement (Christensen and Adrian, 2001, 4th Int. Symp. on PIV). Integrating the material acceleration, avoiding regions dominated by viscous diffusion, provides the pressure distribution. The two cameras are carefully calibrated to achieve a 0.06 pixel average misalignment between them. The system is presently being used to measure the instantaneous pressure and velocity distributions of a 2D cavity flow field in a water tunnel. Three reference pressure transducers at different locations are used for calibration.