Review of Computational Fluid Dynamics Analysis in Biomimetic Applications for Underwater Vehicles

Biomimetics, which draws inspiration from nature, has emerged as a key approach in the development of underwater vehicles. The integration of this approach with computational fluid dynamics (CFD) has further propelled research in this field. CFD, as an effective tool for dynamic analysis, contributes significantly to understanding and resolving complex fluid dynamic problems in underwater vehicles. Biomimetics seeks to harness innovative inspiration from the biological world. Through the imitation of the structure, behavior, and functions of organisms, biomimetics enables the creation of efficient and unique designs. These designs are aimed at enhancing the speed, reliability, and maneuverability of underwater vehicles, as well as reducing drag and noise. CFD technology, which is capable of precisely predicting and simulating fluid flow behaviors, plays a crucial role in optimizing the structural design of underwater vehicles, thereby significantly enhancing their hydrodynamic and kinematic performances. Combining biomimetics and CFD technology introduces a novel approach to underwater vehicle design and unveils broad prospects for research in natural science and engineering applications. Consequently, this paper aims to review the application of CFD technology in the biomimicry of underwater vehicles, with a primary focus on biomimetic propulsion, biomimetic drag reduction, and biomimetic noise reduction. Additionally, it explores the challenges faced in this field and anticipates future advancements

Low Energy, Passive Acoustic Sensing for Wireless Underwater Monitoring Networks

Ph. D. ThesisThis thesis presents the research conducted to develop low energy passive acoustic monitoring (PAM) algorithms. There are many signal processing techniques and machine learning systems which are capable of detecting and classifying target signals. However, this project aims to produce PAM detection and classification results using a low energy budget. The benefit of using this approach is that physical devices can be developed and deployed in open sea for several months using only battery power. This opens up the deployment area to very deep water where power sources are not readily available. Using passive acoustic communication to relay the detection data produced by the algorithm, it is expected that these systems could form an underwater network of sensor nodes. There are three targets for passive acoustic detection/classification included in this thesis, which are motorised surface vessels, cetacean clicks and cetacean whistles. The surface vessel detection method is based on a low energy implementation of Detection of Envelope Modulation On Noise (DEMON). Vessels produce high frequency modulated noise during propeller cavitation which the DEMON method aims to extract for the purposes of automated detection. The vessel detector design has different approaches with mixtures of analogue and digital processing, continuous and duty-cycled sampling/processing. The detector has been integrated with a low cost/power acoustic modem platform to provide acoustic communication of data in near real time. The vessel detector has been deployed at 20m depth for a total of 84 days in the North Sea providing a large data set, which the results are based on. Open sea field trial results have shown the detection of single and multiple vessels with a 94% corroboration rate with local Automatic Identification System (AIS) data. Results have shown additional information about the detected vessel, such as the number of propeller blades, can been extracted solely based on the detection data. The attention to energy efficiency has led to an average power consumption of 11.4mW enabling long term deployments of up to 6 months using only four alkaline C cells. Additional battery packs and a modified enclosure could enable a longer deployment duration. As the detector was still deployed during the first UK lockdown, the impact of Covid-19 on North Sea fishing activity has been captured in the results. Cetacean click detection is based on identifying and classifying the high frequency impulsive click trains created by cetaceans during navigation and foraging. A low energy method of detecting these vocalisations is proposed alongside a statistical based method of classification. The algorithm developed was tested using real recordings of cetacean activity and comparisons have been conducted against a commercially available cetacean monitoring system. The results show that the energy efficient algorithm produces comparable results to the commercial system when real recordings are processed. The cetacean whistle detection algorithm is based on a low energy phase locked loop (PLL) technique. PLL methodology has been adapted for this project to aid in developing a low energy approach to detecting cetacean whistles by tracking the sweeps in frequency they produce. Results are based on offline processing using real recordings of these animals. The results have shown a 75% success rate when comparing against human analysis of the recording. Future work includes the further development of the cetacean related algorithms into fully deployable, battery-powered, nodes for open sea field trails. The future work related to vessel detection includes adding a tracking feature to the passive acoustic monitoring technology.Engineering and Physical Sciences Research Council (EPSRC

The Victorian Naturalist

v.116 (1999

Aeronautical Engineering: A special bibliography with indexes, supplement 51

This bibliography lists 206 reports, articles, and other documents introduced into the NASA Scientific and Technical Information System in November 1974

A comparison study of biologically inspired propulsion systems for an autonomous underwater vehicle

The field of Autonomous Underwater Vehicles (AUVs) has increased dramatically in size and scope over the past two decades. Application areas for AUVs are numerous and varied; from deep sea exploration, to pipeline surveillance to mine clearing. However, one limiting factor with the current technology is the duration of missions that can be undertaken and one contributing factor to this is the efficiency of the propulsion system, which is usually based on marine propellers. As fish are highly efficient swimmers greater propulsive efficiency may be possible by mimicking their fish tail propulsion system. The main concept behind this work was therefore to investigate whether a biomimetic fish-like propulsion system is a viable propulsion system for an underwater vehicle and to determine experimentally the efficiency benefits of using such a system. There have been numerous studies into biomimetic fish like propulsion systems and robotic fish in the past with many claims being made as to the benefits of a fish like propulsion system over conventional marine propulsion systems. These claims include increased efficiency and greater manoeuvrability. However, there is little published experimental data to characterise the propulsive efficiency of a fish like propulsive system. Also, very few direct experimental comparisons have been made between biomimetic and conventional propulsion systems. This work attempts to address these issues by directly comparing experimentally a biomimetic underwater propulsion system to a conventional propulsion system to allow for a better understanding of the potential benefits of the biomimetic system. This work is split into three parts. Firstly, the design and development of a novel prototype vehicle called the RoboSalmon is covered. This vehicle has a biomimetic tendon drive propulsion system which utilizes one servo motor for actuation and has a suite of onboard sensors and a data logger. The second part of this work focuses on the development of a mathematical model of the RoboSalmon vehicle to allow for a better understanding of the dynamics of the system. Simulation results from this model are compared to the experimental results and show good correlation. The final part of the work presents the experimental results obtained comparing the RoboSalmon prototype with the biomimetic tail system to the propeller and rudder system. These experiments include a study into the straight swimming performance, recoil motion, start up transients and power consumption. For forward swimming the maximum surge velocity of the RoboSalmon was 0.18ms-1 and at this velocity the biomimetic system was found to be more efficient than the propeller system. When manoeuvring the biomimetic system was found to have a significantly reduced turning radius. The thesis concludes with a discussion of the main findings from each aspect of the work, covering the benefits obtained from using the tendon drive system in terms of efficiencies and manoeuvring performance. The limitations of the system are also discussed and suggestions for further work are included

Aeronautical Engineering: A special bibliography with indexes, supplement 48

This special bibliography lists 291 reports, articles, and other documents introduced into the NASA scientific and technical information system in August 1974