Tandem Interference Effects of Flat Noncavitating Hydrofoils

Experimental measurements were made of the interference effect of two submerged, flat, noncavitating hydrofoils of finite span in tandem. the surface wave generated by a single foil was measured in the longitudinal and lateral directions. Downwash angles were determined from the experimental data for various foil separations and submergences. Comparison of the results with theory was favorable. Limited measurements were also made of the oscillatory lift and dag forces for a foil moving through a progressive wave train. The data agreed with quasi-steady theory for the lower frequencies of encounter. At the higher frequencies of encounter, consideration of unsteadiness effects improved the correlation.