Correlation of Theoretical Predictions of Propeller-Induced Hull Pressures with Available Data.

A method has been developed to calculate the blade frequency point pressure on a hull surface in the presence of a propeller and a free water surface. The approach is based on that previously employed in calculating the propeller-induced hull forces in which the hull is represented by a source distribution smeared over the hull surface whose strength is determined through the solution of a Fredholm integral equation of the 2nd kind in terms of specified propeller-induced velocities. Point pressures are determined by superposing the free-space pressure emanating from the propeller through its fanning action on the pressure due to the diffraction potential. A series of calculations was performed for the case of a model tanker tested extensively at the Norwegian Experimental Tank (Ship and Ocean Labroatory, Norwegian Hydrodynamic Laboratories. The agreement between experimental and predicted values varies from point to point; in general, the maximum deviation of amplitude is between + or - 30%, but the phases are in poor agreement. A new method is suggested in which the hull is represented by a doublet distribution rather than a source distribution. This approach which reduces computing time considerably permits improved accuracy and results in much better correlation between experimental and calculated values.