Freestream Velocity Corrections for Two-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 nse of splitter plates, the peculiar effects of this testing arrangement on the velocity correction are not well documented. The use of splitter plates in the test section has several advantages, but there are unfortunate consequences (such as spillage, entrainment, and blockage to varying degrees) that require the freestream velocity to be measured directly between the splitter plates with the airfoil in the test section. In this case, the standard velocity correction for wall interference is not sufficient. An additional correction must be made to account for the change in velocity ahead of the airfoil model caused by the circulation about the airfoil. The results reveal that failing to correct for the circulation effect can yield significant errors in the aerodynamic coefficients. The proposed velocity measurement 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.