Sidewall boundary-layer corrections in subsonic, two-dimensional airfoil/hydrofoil testing

Historically, in water or wind tunnels without sidewall boundary-layer control, balance-measured lift and pitching moment data have been acceptable, whereas drag data have varied by as much as an order of magnitude from previous reference data. An experimental wind tunnel program was conducted to investigate the parameters that influence these subsonic, two-dimensional, balance-measured airfoil/hydrofoil section characteristics. From the results of this program, the sidewall boundary layer was identified as the primary factor contributing to the erroneous drag measurements. A correction procedure based on the airfoil/hydrofoil geometry, the flow environment, and the measured data was developed. Corrected data from the subject test program and from similar programs in other experimental facilities for both symmetrical and cambered sections are in good agreement with the reference data.