Unsteady Lifting Surface Theory for a Marine Propeller of Low Pitch Angle With Chordwise Loading Distribution

Abstract : This study is third in a series of investigations applying the unsteady lifting surface theory to the marine propeller case. In this investigation, the surface integral equation is solved for a mathematical model where the chordwise loading is taken as the first term of Birnbaum's lift distribution (flat-plate chordwise distribution), in conjunction with Glauert's lift operator, which, in essence, satisfies the chordwise boundary conditions by a weighted average. It is shown that this model is an improvement over the modified Weissinger model used previously in this series, because it contains as a nucleus the exact two-dimensional solution, and thus it provides a sounder basis for dtermining the three-dimensional effects. The blade-loading is determined for a propeller operating in flow disturbanccs induced by the presence of a hull and by the blade-camber effect. The stationary loading obtained by the present model is about 10% less than that obtained by the modified Weissinger model, whereas the nonstationary loading is slightly larger. (Author)