Wave Distortion Methodology for Experimental Mixed-Scale Testing of Underwater Vehicle Docking

Abstract Autonomous Underwater Vehicles (AUVs) are essential for a variety of marine applications but are typically constrained by battery capacity (limiting their range and duration) and necessary ancillary infrastructure. Recent advancements in Wave Energy Converter (WEC) technology offer the potential to extend AUV missions through docking and electrical power recharge. However, a significant challenge in utilizing wave-powered AUV systems is docking near the energetic ocean surface. This situation contrasts with traditional docking environments typically characterized by calmer, wave-minimal, deep-water conditions. Scaled physical model testing provides a robust methodology for proof-of-concept testing. However, laboratory testing WEC-AUV docking presents a complex mixed-scale challenge. Firstly, in the laboratory, water depth and wave conditions are at model scale, whereas the dock and AUV remain at field scale. Secondly, unlike field conditions where the dock is physically connected to a WEC, laboratory setups cannot generally accommodate a field-scale WEC. This paper presents a novel method to ‘distort’ wave and docking conditions within a wave tank to 1) accurately simulate subsea dynamics, and 2) a unique hardware-in-the-loop methodology to replicate WEC-AUV dock motions with ocean waves. The paper details the necessary theory required to distort wave and docking conditions to independently match the ocean’s water particle and dock acceleration or velocity amplitude. In addition, the approach ensures consistency in spectral shapes between lab and ocean settings and demonstrates an asynchronous testing procedure simulating dock motions in the wave tank.