Novel experiments on the dynamics of amphibious craft during surf zone transit

Abstract

This article presents the results of a comprehensive experimental study of amphibious vehicle dynamics during surf zone transits. The motions and loads of multi-mode vehicles traversing breaking waves is relevant to operators, designers, and simulators seeking to extend the operation of existing and new platforms into the littorals. Here we present the results from a first-of-its-kind experimental campaign to quantify the dynamics of a free-running amphibious model during surf zone transit.The amphibious vehicle studied was the IIHR Model Quadski, a model-scale free-running craft prototyped at The University of Iowa. Testing was conducted in a wave basin facility, equipped with an artificial beach to produce model-scale breaking waves up to heights of 37 centimeters. Vehicle attitudes, wave elevations, and maneuvering inputs were recorded during repetitious crossings of varied wave conditions in outbound, inbound, and oblique transit trajectories.Analysis of high-level statistics and pairwise comparisons show that decreased momentum entering the surf zone from shore resulted in significantly longer transit times and additional wave encounters, even with equal waterjet thrust. Furthermore, vehicle dynamics during seaward transits were considerably larger in amplitude and shorter in period than landward transits.