ANALYSIS OF STEADY AND UNSTEADY PERFORMANCES FOR 3-D AIRWINGS IN THE VICINITY OF THE FREE SURFACE

This paper describes the mathematical formulation for the calculation of steady and unsteady forces of 3-D wings flying near the free surface. Using the potential based panel method distributing dipoles and sources on the foil surfaces, steady and unsteady lift and drag forces are calculated for wings with different sections, angle of attacks and flying heights. Those calculated are compared with other calculated results published and also with experimental results conducted in a wind tunnel. It is found that the numerical results for the steady problem show similar patterns as the experimental results, but there are some discrepancies in magnitude. For the unsteady problem, it is found that the wave effect CL, is negligible at wave lengths shorter than 1.0c and that unlike for 2-D wing cases, the ground effect of a wing in waves is lower than that in the flat ground.