Session: 06-08-02 Model Tests

Submission Number: 156599

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

Autonomous Underwater Vehicles (AUVs) are essential for a variety of marine applications but are typically constrained by battery capacity, limiting their range and duration. Recent advancements in Wave Energy Converter (WEC) technology offer the potential to extend AUV missions by harnessing wave power. A significant challenge in utilizing wave-powered AUV systems is docking near the energetic ocean surface, a situation that contrasts with traditional docking environments typically characterized by calmer, wave-minimal conditions. The integration of an AUV docking port with a WEC requires careful consideration of the dynamic wave environment.

This paper presents a novel method to adapt wave conditions within a wave tank to accurately simulate those of the ocean, facilitating effective AUV docking tests under controlled conditions. We developed equations to distort wave conditions in the laboratory to match the ocean's water particle velocity and acceleration, maintaining a constant non-dimensional parameter kh, which combines the wave number (k) and the water depth (h). This approach ensures that the ratios of horizontal to vertical water particle velocities and accelerations, as well as the shape of the spectrum density of random waves, are consistent between the lab and ocean settings.

Testing AUV docking in the wave tank presents a complex mixed-scale challenge. In the laboratory, wave conditions are scaled down, whereas the dock and AUV remain at full scale. In addition, unlike oceanic conditions where the dock is physically connected to a Wave Energy Converter (WEC), our laboratory setup cannot accommodate a full-scale WEC. To address this, we developed a method for simulating dock motions in the wave tank. Our approach involves scaling up wave conditions from the wave tank to ocean conditions, predicting dock/WEC motions through numerical simulation, and then scaling down these motions for wave tank applicability. The simulated dock motions are synchronized with waves in the wave lab to create a complete dynamic environment for AUV docking.

Extensive wave tank testing validated our methodology, confirming the effectiveness of our approach in distorting wave conditions to simulate real ocean dynamics. The results were subsequently used to refine and validate AUV docking algorithms.

Presenting Author: Bryson Robertson Oregon State University

Presenting Author Biography: Bryson Robertson, Ph.D.: Director, Pacific Marine Energy Center, Associate Professor of Civil and Construction Engineering, OSU. His research is focused on wave energy converter (WEC) numerical and experimental modeling, the development of open-source WEC prototypes, grid value propositions for wave and offshore wind energy, and improved characterization of relevant ocean conditions. Dr. Robertson received his Ph.D. (2013) in Environmental Engineering from the University of Guelph & Queens University, and his B.Eng in Mechanical Engineering from the University of Victoria (2005). He is a Technical Board member for the Testing Expertise and Access for Marine Energy Research (TEAMER) and is a committee member with Int. Electrotechnical Commission’s (IEC).