A GENERALIZED THEORETICAL INVESTIGATION OF THE HYDRODYNAMIC PITCHING MOMENTS EXPERIENCED BY V-BOTTOM SEAPLANES DURING STEP-LANDING IMPACTS AND COMPARISONS WITH EXPERIMENT

摘要

A theoretical investigation is made of the hydrodynamic pitching moments experienced by V-bottom seaplanes during step—landing impacts. The entire immersion process is analyzed from the instant of initial contact until the seaplane rebounds from the water surface. In the analysis the primary flow about the immersed portion of a keeled float or hull is considered to occur in transverse flow planes and the virtual mass concept is applied to calculate the reaction of the water to the motion of the seaplane.nIt is shown that the pitching moment and the center-of-pressure location may be represented in generalized form by means of dimensionless variables which take into account the effects of such factors as the seaplane weight, angle of dead rise, trim angle, and initial velocity. The variation of these coefficients during an impact is governed by the magnitude of a single parameter, called the approach parameter K, that is determined by the trim and the initial flight-path angle and permits reduction of the impact variables to a common basis.