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.