Design Of Underwater Vehicle Research Articles

Enhancing stability and performance of flexible membrane structures in wake flows through jet flow control

This study investigates jet flow control on flexible membrane structures placed in the wake of a stationary cylinder to enhance performance and stability. Flexible membranes, found in both nature and engineering, often face nonlinear disturbances where passive deformation is insufficient. Inspired by adaptive fish fins, we explore active flow control strategies using a high-fidelity fluid–structure interaction solver to simulate the dynamics of a flexible membrane downstream of a cylinder. High-momentum jet flows with different momentum coefficients are applied at membrane leading edge to modulate the boundary layer flow features. Numerical simulation results reveal that jet flow control can weaken the wake interference effect on the membrane dynamics, resulting in lift improvement and flow-induced vibration suppression. The flow separation within the boundary layer is suppressed by high-momentum jet flows, thereby enhancing lift performance and stability. The reason of the flow-induced vibration suppression is attributed to the redistribution of the vibration energy in high-order structure modes excited by jet flows. Our results demonstrate that jet control has great potential for optimizing the performance and stability of flexible membrane structures in complex flow environments, providing valuable insights into the design of next-generation intelligent underwater vehicles and ships with flexible membrane propulsion systems.

Design and Implementation of a Bone-Shaped Hybrid Aerial Underwater Vehicle

Design and Implementation of a Bone-Shaped Hybrid Aerial Underwater Vehicle

Mechanical properties and failure behavior of additively manufactured Al2O3 lattice structures infiltrated with phenol-formaldehyde resin

The lightweight design and load-bearing capacity of underwater vehicles remain perennial focal points. Ceramic lattice structures (CLSs) offer significant weight reduction while maximizing structural strength; however, their inherent brittleness poses a limitation. To optimize the performance of CLSs for underwater vehicle applications, a biomimetic Al2O3/phenol-formaldehyde (PF) resin composite structure (APCS) was proposed and fabricated by infiltrating additive-manufactured Al2O3 lattice structures (ALSs) with PF. Comprehensive assessments of the quasi-static mechanical properties were conducted using both experimental and simulation methods. The specific compressive strength and specific energy absorption of the APCSs under quasi-static compressive loading exhibited remarkable improvements, with the maximum values achieved from the body-centered cubic (BCC)/PF structure increasing by ∼15.23 and ∼307.93 times, respectively. In contrast to ALSs, the failure process of APCSs was gradual, with the confining pressure introduced by the PF promoting transverse crack propagation and layer-by-layer failure, thereby strengthening the ceramic lattice. Toughing mechanisms (i.e., crack arrest, crack deflection, and branching) were also observed in the APCSs. Furthermore, the simulation results aligned well with the experimental results, providing an in-depth analysis of internal damage and crack propagation. The improvements introduced by the composite structure in this study provide a reliable approach for obtaining lightweight and strong materials, thereby accelerating the application of ceramic-based materials in underwater vehicles.

Numerical simulations of bio-inspired approaches to enhance underwater swimming efficiency

The present study discusses the numerical simulation results of swimming similar to manta rays. The complex three-dimensional kinematics of manta rays were implemented to unravel the intricacies of its propulsion mechanisms by using the discrete vortex method (DVM). The DVM replaces the requirement for a structured grid across the computational domain with a collection of vortex elements. This method simplifies grid generation, especially for intricate geometries, resulting in time and effort savings in meshing complex shapes. By modeling the pectoral fins with discrete panels and utilizing vortex rings to represent circulation and wake, the study accurately computes the pressure distribution, circulation distribution, lift coefficient, and thrust coefficient of the manta ray. This study focuses on the modulation of aerodynamic performance by altering the span length and the length change ratio during the downstroke and upstroke motion (SV). The manta ray's three-dimensional vortex configurations comprise a combination of vortex rings, vortex contrails, and horseshoe vortices. Analysis of the three-dimensional vortex structure indicates the presence of multiple vortex rings and horseshoe vortex rings at higher SV values, while adequate formation of horseshoe vortices is not observed at lower SV values. In terms of propulsive performance, both lift and thrust increase with SV, while the propulsive efficiency demonstrates its peak at SV = 1.75. The analysis reveals that at higher SV values, the net thrust generated primarily originates from the tip of the fins. Moreover, the study illustrates a significant enhancement in propulsive efficiency, particularly in association with optimal Strouhal numbers ranging between 0.3 and 0.4. The key findings of this study may be used in efficient design of agile autonomous underwater vehicles for marine exploration and surveillance applications.

Rapid data-driven individualised shape design of AUVs based on CFD and machine learning

ABSTRACT The shape design of autonomous underwater vehicles (AUVs) has an essential influence on their hydrodynamic performance. In this study, a data-driven approach is proposed based on computational fluid dynamics (CFD) and machine learning to efficiently design the hydrodynamic shape of AUVs with different sailing velocities, angles of attack (AOAs) and volumes. Based on the data-driven approach, a shape optimisation design for AUVs is established. Moreover, the variation of optimal shape with the design constraints of AOA, velocity and volume is also explored, and the results prove that a relatively larger body with a sharper head is more beneficial for the Myring shape AUVs sailing with a higher velocity and a larger AOA. The results of CFD calculations and those of the data-driven approach are compared, and a circulating flume test is carried out to prove the reliability of CFD method. The comparison verifies the reliability of the optimisation result.

A New Multi-Mechanism Synergistic Acoustic Structure for Underwater Low-Frequency and Broadband Sound Absorption

The acoustic absorption characteristics of anechoic coatings attached to the surface of underwater vehicles are closely related to their acoustic stealth. Owing to the essential property of local resonance, the narrow sound-absorption band cannot meet the underwater broadband sound absorption requirements. To this end, a multi-mechanism synergistic composite acoustic structure (MMSC−AS) was designed according to the integration of multiple acoustic dissipation mechanisms in this paper. Then, the acoustical calculation model for MMSC−AS was developed by using the graded finite element method (G-FEM), and the feasibility and the correctness of the established acoustical calculation model were verified. The underwater sound absorption behaviors of MMSC−AS were studied, and the optimization of the sound absorption characteristics of the MMSC−AS was also carried out. The results indicated that the calculation accuracy of the G-FEM was better than that of the FEM under the condition of the same mesh elements. Moreover, there were many sound wave regulation mechanisms in the MMSC−AS, and the synergy between the mechanisms enriched the mode of sound acoustic energy dissipation, which could widen the absorption band with effect. This study provides theoretical and technical basis for breaking through the challenge of low-frequency and broadband acoustic structure design of underwater vehicles.

Design and Analysis of Self-Energising Unmanned Underwater Vehicle (UUV)

This research focuses on the development of a self-energizing underwater vehicle that utilizes wave energy to power its circuit. The objective of the research work is to demonstrate the feasibility of harnessing renewable energy sources in an underwater environment and showcase the potential for sustainable power generation. To ensure the structural integrity of the vehicle under water, rigorous simulation analysis has been conducted using ANSYS software. The hull design has undergone thorough scrutiny to determine its ability to withstand water pressure at depths of up to 5 meters. The simulation results confirm that the submarine's hull design is robust and capable of withstanding the expected operating conditions. This study holds great significance in the field of marine engineering as it explores alternative energy sources for underwater applications. By harnessing wave energy, this work contributes to the development of sustainable technologies that can potentially revolutionize underwater operations. The use of renewable energy sources minimizes environmental impact and reduces reliance on traditional power sources. Throughout this research, challenges were encountered, including optimizing the turbine system efficiency, ensuring reliable power transfer, and maintaining the structural integrity of the submarine. These challenges were addressed through careful design considerations and iterative improvements. The knowledge gained from this study can be applied to various underwater applications such as marine exploration, environmental monitoring, and data collection. Future research and development should focus on enhancing the turbine design, integrating advanced power management systems, and conducting field tests to validate the system's performance in real-world-scenarios.

Analysis of Available Yawing Moment of an Autonomous Underwater Vehicle Model in Simulation Frame

Research endeavors on the design and control techniques of Autonomous Underwater Vehicles (AUVs) have been going on for a long time. In the present study, the yaw motion of a small submerged underwater vehicle is investigated and visualized as a direct result of changes in the rudder tilt angle and forward velocity. The numerical analysis is performed in ANSYS-Fluent software. The turbulent flow field has been modeled using Shear Stress Transport (SST) k-ω model. A grid independence test has been conducted to ensure the validity of the findings. The forces on the rudder and the available yaw moment have been obtained for different combinations of the AUV’s rudder tilt angle and forward velocity. The trend has intuitively been consistent and agreed with the basic concept of hydrodynamics

Generating high-efficiency swimming kinematics using hydrodynamic eigenmode decomposition

This paper explores the use of hydrodynamic eigenmode decomposition as a means of generating optimal swimming kinematics of slender three-dimensional bodies. The eigenvectors of the unsteady hydrodynamic system are used as basis functions for the response to external forcing, such as perturbations generated by the deformation of the body. Exploiting the orthogonality of the modes, we show that swimming according to a single appropriately selected hydrodynamic eigenmode results in high-efficiency swimming. To demonstrate this result, we use an inviscid three-dimensional vortex lattice model to investigate the hydrodynamic eigenmodes of a selection of geometries. We find that for all of the body geometries tested, hydrodynamic efficiency far exceeding that of pure heaving or pitching can be achieved. All eigenmodes tested produce high-efficiency motion, as long as the beat frequency is higher than the mode's “cut-in” frequency for thrust generation. The eigenmodes show qualitative similarity to swimming patterns observed in nature and also correspond well to the existing classifications of undulatory and oscillatory swimming. This study demonstrates that the hydrodynamic eigenmode analysis can generate high-efficiency swimming kinematics based only on information about the body and wake geometry, and as such, this method has significant potential for further development and application to autonomous underwater vehicle design.

Adaptive Finite-Time Trajectory Tracking Control for Coaxial HAUVs Facing Uncertainties and Unknown Environmental Disturbances

In this paper, the problems of system design, dynamic modeling, and trajectory tracking control of coaxial hybrid aerial underwater vehicles (HAUVs) with time-varying model parameters and composite marine environment disturbances are investigated. It is clear that a stable transition between different media remains a challenge in the practical implementation of amphibious tasks. For HAUVs, accurate dynamic modeling to describe complex dynamic variations during vehicle takeoff from underwater to air is a huge challenge. Meanwhile, due to the rapid changes in model parameters and the external environment, vehicles are likely to fall into the sea during the cross-domain process. An integrated continuous dynamic model considering hydrodynamic changes is established by introducing a linear switching coefficient during the process of trans-medium motion. A nonsingular fast terminal sliding-mode control (NFTSMC) algorithm combined with adaptive technology is used to design the position and attitude of the controller. With no previous knowledge of external interferences and lumped uncertainties of the HAUV, the adaptive NFTSMC (ANFTSMC) algorithm achieves the control objectives; at the same time, the inherent chattering problems of sliding mode control (SMC) are weakened. The finite-time stability of the global system is proven strictly using a series of mathematical derivations based on Lyapunov theory. The effect of the controller applied is analyzed through a series of simulations with representative working conditions. The results show that the proposed ANFTSMC can realize a “seamless” air–water trans-medium process, which proves the superiority and robustness of the proposed control algorithm.

Kalypso Autonomous Underwater Vehicle: A 3D-Printed Underwater Vehicle for Inspection at Fisheries

Abstract In fish farms, a major issue is the net cage wear, resulting in fish escapes and negative impact on fish quality, due to holes and biofouling of the nets. To minimize fish losses, fisheries utilize divers to inspect net cages on a weekly basis. Aquaculture companies are looking for ways to maximize profit, and reducing maintenance costs is one of them. Kefalonia Fisheries spend 250,000 euros yearly on diver expenses for net cages maintenance. This work is about the design, fabrication, and control of an inexpensive autonomous underwater vehicle (AUV) intended for inspection in net cages at Kefalonia Fisheries S.A. in Greece. Its main body is 3D printed, and its eight-thruster configuration grants it six degrees-of-freedom. The main objective of the vehicle is to limit maintenance costs by increasing inspection frequency. The design, fabrication, electronic components, and software architecture of the AUV are presented. In addition, the forces affecting kalypso, mobility realization, navigation, and modeling are quoted along with a flow simulation and the experimental results. The proposed design is adaptable and durable while remaining cost-effective, and it can be used for both manual and automatic operations.

An adaptive neural network with nonlinear FOPID design of underwater robotic vehicle in the presence of disturbances, uncertainty, and obstacles

An adaptive neural network with nonlinear fractional-order PID (ANNFOPID) controller design is proposed for underwater robotic vehicle (URV) to solve the path tracking problem. The path tracking problem is caused by disturbances and unknown uncertainties of the underwater vehicle dynamic model. The disturbances were presented with the URV model to evaluate the performance of the ANNFOPID controller to reject the disturbances. At the same time, an obstacle avoidance model has been presented with ANNFOPID controller to evaluate the controller ability to maneuver around different obstacle locations. A radial base function (RBF) has been used to estimate both of the disturbances and the unknown uncertainties of the dynamic model. An improved slime mould algorithm (ISMA) is presented to invent a new trajectories for the underwater vehicle and enhance the ability of the URV to overcome the obstacles problems. At the end, the results obtained show that the ANNFOPID controller present an outstanding performance in comparison with other existing works to overcome the disturbances, unknown uncertainties, and obstacles problems effectively.

Theoretical Study of Supercavitation Bubble Formation Based on Gillespie’s Algorithm

Understanding the creation and development of a supercavitation bubble is essential for the design of supercavitational underwater vehicles and applications. The pressure field of the supercavitation bubble is one of the most significant factors in these processes, and it should be taken into account in the analysis. The underwater vessel is surrounded by a supercavitation bubble which is, in fact, an inhomogeneous fluid containing cavities (also described as microbubbles). The distribution of the cavities in the supercavitation volume dictates the pressure field and thus determines the stresses and forces that act on the vessel and affect its motion and stability. In this research, we suggest a new approach to studying the bubbles’ formation and learning about the cavities’ distribution in the low-pressure volume that envelops the underwater vehicle. We used Logvinovich’s principle to describe a two-dimensional ring of fluid that is created at the front edge of the supercavitation body and moves downstream along the vessel. To describe the distribution of the cavities we used Gillespie’s algorithm, which is usually used to describe biological and chemical systems. The algorithm succeeded in describing the random movement of the cavities in the cross-section under various conditions and also in describing their distribution and effects on the macroscopic system. A few factors of the physical characteristics of the fluid and the flow conditions were examined (the initial bubble supply, and the rate coefficients of creation and collapse). The results led to the conclusion that with an examination of those factors and using Gillespie’s algorithm, predictions of the distribution and thus the development of supercavitation could be achieved. The main finding of the analysis was that asymmetric development of the bubbles took place, in spite of the symmetry of the physical problem, as observed in high-resolution experiments.

Optimum design of acoustic stealth shape of underwater vehicle model with conning tower

We present an optimization algorithm for achieving optimal acoustic stealth performance during designing an underwater vehicle shape in the free field using COMSOL-MATLAB integrated software. A component superposition method based on phase interference is adopted to simplify and decompose a nonaxisymmetric complex underwater vehicle model into two main parts: the hull and the conning tower. The shape of underwater vehicle hull is described mathematically with a sequence of undetermined coefficients for optimization. The basic mathematical principle of the proposed method is Kirchhoff approximation, also called planar element method (PEM). Additionally, some examples and experimental results show that this method can realize the automatic optimization design of acoustic stealth shapes for underwater vehicle model in a given frequency band and acoustic incident angle range. The underwater vehicle design has a smooth appearance with low target strength (TS) or angle detection rate for most detection angles and frequency bands after optimized.

Self-Propelled Swimming of a Flexible Propulsor Actuated by a Distributed Active Moment

The self-propelled swimming of a flexible propulsor is numerically investigated by using fluid-structure interaction simulations. A distributed active moment mimicking the muscle actuation in fish is used to drive the self-propulsion. The active moment imposed on the body of the swimmer takes the form of a traveling wave. The influences of some key parameters, such as the wavenumber, the amplitude of moment density and the Reynolds number, on the performance of straight-line swimming are explored. The influence of the ground effect on speed and efficiency is investigated through the simulation of near-wall swimming. The turning maneuver is also successfully performed by adopting a simple evolution law for the leading-edge deflection angle. The results of the present study are expected to be helpful to the design of bio-inspired autonomous underwater vehicles.

A study on the cavitating flow around an elliptical disk-shaped cavitator for non-body-of-revolution underwater vehicles

Supercavitation has been recently presented as an effective method for the drag reduction of underwater vehicles. However, maintaining the supercavitating state requires a lot of energy, making vehicles difficult to control. Therefore, it is necessary to design an underwater vehicle with low drag in the fully wetted state while being able to move at ultra-high speed in the supercavitating state. In this study, a detachable fairing design for underwater vehicles is proposed, which has the advantage of increasing the total voyage and avoiding the problem of difficult steering in the supercavitating state. On the other hand, the study of non-body-of-revolution (non-BOR) has become a prevalent area of interest in the shape design of underwater vehicles. The cavity generated by an elliptical disk-shaped cavitator is studied numerically. It is found that the cavity profile on the cross-section near the cavitator is approximately elliptical. The cavity length of an elliptical disk-shaped cavitator is almost the same as that of a disk-shaped cavitator when they have the same inflow area. Based on these two characteristics, the parameters of the internal elliptical disk-shaped cavitator are optimized, which provides a promising strategy for the issue of cavitators increasing drag in a fully wetted state.

Drag reduction of turbulent boundary layer over sawtooth riblet surface with superhydrophobic coat

The application of drag reduction tech holds great significance to energy saving. To achieve better drag reduction, we investigated the flow characteristics of the turbulent boundary layer (TBL) over a composite surface made of sawtooth riblets with superhydrophobic coat (rib&SHS), a superhydrophobic surface (SHS), and a smooth surface using particle image velocimetry. The results showed that the drag reduction rate of the composite surface was higher than that of the superhydrophobic surface at the same Reynolds number. When the Reynolds number reached 2015, the drag reduction effect of SHS was almost ineffective (drag reduction was only 1.2%), whereas rib&SHS maintained satisfactory results (drag reduction was 20.2%). By proper orthogonal decomposition (POD), the second-order POD mode showed the tilt angles of the interface of Q2 and Q4 events inside the TBL over rib&SHS, and SHS were reduced compared with the smooth surface in the drag reduction cases. With drag reduction of rib&SHS and SHS, the hairpin vortexes were lifted away from the wall and the distances of vortexes within hairpin vortex packets decreased. Compared with SHS, rib&SHS had a greater effect on hairpin vortexes and hairpin vortex packets because the riblets made the Q2 events of rib&SHS weaker than that of SHS. So, the rib&SHS has a higher drag reduction rate and a larger drag reduction Reynolds number range than the SHS. It can be used to guide the drag reduction design of underwater vehicles.

Jaya optimization algorithm implemented on a new novel design of 6-DOF AUV body: a case study

The novel Jaya Optimization Algorithm (JOA) was utilized in this research to evaluate the efficiency of a new novel design of Autonomous Underwater Vehicle (AUV). The Three Proportional Integral Derivative (PID) controllers were used to obtain the optimum output for the AUV Trajectory, which can be considered as a main side of the research for solving the AUV Performance. The optimization technique has been developed to solving the motion model of the AUV in order to reduce the rotations of trajectory for the AUV 6-DOF Body in the axis’s in x, y and z for the overall positions, velocity were measured in 50 seconds as the velocity compared with the simulated time, and to execute the optimum output for the dynamic kinematics model based on the Novel Euler-6 DOF AUV Body Equation implemented on MATLAB R2021a Version.

Comparative Analysis of the Self-Propelled Locomotion of a Pitching Airfoil near the Flat and Wavy Ground.

In this paper, a pitching airfoil near flat and wavy ground is studied by numerical simulations. The kinematic features of the airfoil and the flow field around it are analyzed to reveal unsteady vorticity dynamics of the self-propelled airfoil in ground effect. The optimal pitching periods at different initial heights above flat ground are obtained, which make the pitching airfoil achieve the maximum lift-to-drag ratio. Compared with flat ground, at the same initial height, the optimal pitching periods vary with the shape of ground. The structure and the strength of the wake vortices shedding from the airfoil are adjusted by the wavelength of ground. This leads to the changes of amplitude and occurrence times of the peak and valley of lift and drag force. The results obtained in this study can provide some inspiration for the design of underwater vehicles in the ground effect.

High-Precision Numerical Research on Flow and Structure Noise of Underwater Vehicle

This paper presents the results of research on the noise generated by an underwater vehicle in the operational state. The study combines the large eddy simulated turbulence model and Lighthill’s acoustic analogy theory and extracts the transient flow field data as the excitation conditions for acoustic calculations. The results of the numerical calculations of the external acoustic field were obtained under vehicle wall pressure pulsation condition, Lighthill volume excitation condition, and the vibration excitation condition of the underwater vehicle. It is found that the noise is concentrated at the front and tail of underwater vehicle, and its level is closely related to the form of vortex shedding. The peak frequency of structural radiation noise of underwater vehicle is consistent with its peak frequency of mean square vibration velocity. The basis for selecting the boundary conditions of the sound field according to the incoming flow conditions is also evaluated. The research results provide a reference for the noise reduction design of underwater vehicles, thus improving their concealment in combat.