Experimental and analytical evaluation of flow in a square-to-square wind tunnel contraction

Flow characteristics within a square-to-square contraction are investigated numerically and experimentally so as to gain additional insight into the contraction design. Measurements of cross-sectional velocity profiles and longitudinal pressure distributions along the wall centerlines are carried out in a contraction prototype and the results are compared to those predicted by the numerical simulations. Finally, the applicability of the nozzle design method, proposed by Fang (ASME J. Fluid Eng. (1997) 454), is assessed. Results show that although the inviscid calculation fails to simulate correctly the part of the nozzle flow near the contracting walls, the general behavior of the flow in the regions away from the wall is in reasonable agreement with the predicted behavior. On the other hand, the relative friction losses along the wall centerlines are about 4.3% relative to the total pressure drop through the contracting duct. After an adjustment is made in the normalization scheme, the measured pressure distributions are in good agreement with the numerically based distribution.