Experimental analysis of submerged flapping foils; implications for autonomous surface vehicles (ASVs)

Abstract

Abstract-Autonomous surface vehicles (ASVs) have proven effective as ocean observing platforms for maritime operations. In most cases it is advantageous to operate ASVs for extensive missions in order to maximize their cost effectiveness. Such long endurance missions require ASVs to be capable of scavenging ambient energy from the surrounding ocean environment.Submerged flapping foils are currently utilized as an effective mechanism to convert ocean wave energy directly into propulsion. The authors propose a novel setup whereby these foils can heave relative to the surface vehicle and, through the application of a power take off (PTO) system, can recover a proportion of the incoming wave energy.Experiments were performed to investigate the coupled response between a surface vehicle and submerged flapping foils within the context of generating power and propulsion from incoming waves onboard ASVs. Results show that the response of a surface vehicle with submerged flapping foils is particularly sensitive to design parameters such as the longitudinal location of the foils and the seakeeping characteristics of the surface vehicle. Through optimising the PTO system, this setup could recover a useful proportion of wave energy for ASV platforms.

Forward Speed Prediction of a Free-Running Wave-Propelled Boat

“…In suitable wave conditions, the wave-induced flapping motion of submerged flapping foils combined with the incident wavy flow results in a time-average thrust force. This thrust can be used to augment the existing propulsion [1], [2], significantly reducing fuel consumption, or used as the primary propulsor [3], [4], eliminating the necessity to carry propulsive energy reserves (e.g., fuel or batteries) for entire journeys. This approach has significant potential for marine vessels, especially for small unmanned vessels, such as autonomous surface vehicles (ASVs), where low cost, low power, and long endurance systems are required.…”

Estimating the Longitudinal Center of Flotation of a Vessel in Waves Using Acceleration Measurements

“…The particulars of the free-running vehicle used are given in Table I. The autonomous surface vehicle, which had two submerged foils for propulsion along the towing tank [28], was tested in head and following regular waves, which were kept at a constant wave height of 0.12 m. The wave frequency was increased from 0.5 Hz to 0.8 Hz at increments of 0.1 Hz as summarised in Table II. The ASV was stationed at the carriage 30 m from the wavemaker and progressed towards the wavemaker in head waves before being turned around and tested in following waves. The period for each run varied from 60 to 180 seconds depending on the forward speed of the ASV and the wave [29].…”

A review of unmanned surface vehicle development

“…Since USVs are capable of both radio and acoustic transmissions, they may be used as communication hubs for network systems between air, sea, and underwater environments, as well as for aiding underwater navigation (Manley, 2008;Manley & Hine, 2011;German et al, 2012). Furthermore, USVs may be designed to operate at sea for months, if not years (Manley & Hine, 2011;Tsourdos e al., 2014;Bowker et al, 2016). Based on these factors, support ships for marine operations may be required only for vehicle launch and recovery, with the rest of the missions being executed and monitored from a ground control station over satellite communication.…”