On the Validity of Predicting Wave-induced Loads on a Submerged Body Using the Superposition of Regular Wave Results

Abstract

The wave-induced loads on an underwater vehicle operating near the surface can negatively affect the performance of the vehicle. Therefore, the ability to predict these loads accurately is desired. Since irregular seaways are a combination of many underlying component waves, there is a large number of various combinations of waves that could produce a given sea state. Thus, it is not practical to test all the potential seaways directly, either experimentally or numerically, that a vehicle might experience. A potential solution is to use superposition to combine the loads from single, regular waves to predict the loads caused by an irregular seaway. This paper explores the validity of that approach. The wave-induced loads on a captive model were experimentally measured in a two-component irregular seaway and in each of the component waves individually. The analysis showed that the load contributions from each underlying wave in the two-component seaway was consistent with the loads from the single wave tests. However, the two-component seaway also contained nonlinear loads, which can not be obtained from the single wave tests. The results show that superposition provides an accurate prediction for the total linear loads but should be supplemented with another approach to include the smaller nonlinear loads.