Bow Wave Analysis of A Simple Hull Form

Abstract

Hitherto the wave analysis has been applied mainly to the direct determination of the total wave-making resistance component and not to the improvement of either the current wave-making resistance theory or the hull form design procedure. To obtain full understanding of the actual wave-making phenomena, the analysis of the bow wave alone, not of the resultant wave, particularly the detection of the inherent wave amplitude is most indispensable.
This paper presents the first example to analyze the wave amplitude function from the measured bow free wave (not from the resultant free wave). Asymptotic expansion of the exact expression for the free wave elevation was applied.
A 2.5 m Wigley model was adopted to measure the bow wave, where a capacity-typed wave recorder was applied. The analyzed bow wave amplitude is compared with the calculation assuming that the equivalent singularity distribution is given by Michell's thin ship approximation. Noticeable is the reduction of the actual wave amplitude not only at the higher θ range but also at the lower θ range. The former may be attributed to the extremely steep wave slope there as is easily expected from the working limit of the linearized theory. However it is very important to clarify the real cause for the inconsistency at the lower θ range. Presently the authors suppose that this may come from the so-called “blocking effect” of ship hull.
To determine this, further approach is urgently desired both from experiment and from theory.