FREESTREAM VELOCITY CORRECTIONS FOR 2-DIMENSIONAL TESTING WITH SPLITTER PLATES

The velocity correction method for two-dimensional wind-tunnel testing is expanded for the case of testing airfoils between splitter plates. Despite the common use of splitter plates, the peculiar effects of th is testing arrangement on the velocity correction are not well documen ted. The use of splitter plates in the test section has several advant ages, but there are unfortunate consequences (such as spillage, entrai nment, and blockage to varying degrees) that require the freestream ve locity to be measured directly between the splitter plates with the ai rfoil in the test section. In this case, the standard velocity correct ion for wall interference is not sufficient. An additional correction must be made to account for the change in velocity ahead of the airfoi l model caused by the circulation about the airfoil. The results revea l that failing to correct for the circulation effect can yield signifi cant errors in the aerodynamic coefficients. The proposed velocity mea surement and correction method provides results that are in agreement with data obtained in the NASA Langley Research Center low-turbulence pressure tunnel facility. The method can be readily implemented in the data acquisition and reduction process.