<p>A typical underwater vehicle design involves a circular cylinder parallel mid-body with hydro-dynamically smooth bow and stern shaped end sections. Although the end shapes of a vehicle improve its performance, necessitating them on the actual vehicle, they are often numerically difficult to handle when predicting the wave-induced loads on the vehicle design. Since the parallel mid-body portion usually makes up the vast majority of the length of the vehicle, it is possible that the exact end shape of the vehicle has little impact on the wave-induced loads. Extending the parallel mid-body shape over the entire vehicle length would make numeric model dramatically simpler. In this study we use an existing analytical solution to highlight the possible differences that could exist in the wave-induced heave forces on a vehicle with hemispheric end caps to one with an extended parallel mid-body and flat end faces. The wave-induced heave forces on these two model shapes was then experimentally measured in a tow tank with wavemaking capability to determine if the impact of the vehicle end shape is as important as the analytical solution predicts. For the model with hemispheric end caps, we tested one model where the end caps represented 10 percent of the model length and another model where they represented 20 percent of the model length. Since forward speed could potentially cause the flow field around the two different bow shapes to be substantially different due to the blunt nature of the flat face model, both zero speed and forward speed cases were also examined. For a stationary body, the experimental results showed that the end shape of the model has little effect on the wave-induced heave force even though the analytic result predicts a marginal impact. Surprisingly, even with forward speed, the blunt flat face end shaped model does not experience a significant change in the wave-induced heave force either. The small change that does occur is captured fairly accurately by the potential flow analytic solution.</p>

On the Role That the End Shape of an Underwater Vehicle Plays on Wave-Induced Heave Forces

Paper Proceedings: https://asmedigitalcollection.asme.org/OMAE/OMAE2021/volume/85116

OMAE 2021

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