Browsing by Author "Jeans, Tiger"
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Item An evaluation of force estimation models for axisymmetric hull and sail configurations in translation at drift(University of New Brunswick, 2019) Carson, Meghan Ashley; Jeans, Tiger; Holloway, GordonAn evaluation of current in-plane and out-of-plane force and moment models was performed for a generic submarine model at drift. Computational solutions were developed for an axisymmetric hull and sail configuration at small to moderate drift angles, and the results were validated through comparison with experimental results. Existing research provides either qualitative explanations of the flow patterns created, or quantitative results for the overall forces and moments on the full submarine configuration. Using Computational Fluid Dynamics (CFD) fills a gap in the current literature by providing force and vorticity distributions on the body. The existing algorithm was found to adequately predict the in-plane sideforce and rolling moment coefficients at all drift angles, while the yawing moment coefficient is overestimated. The out-of-plane force and moment coefficients for downforce and pitching moment are accurately estimated for angles of drift at or below 10°. At higher angles, these coefficients are significantly over-predicted, mainly due to particular model assumptions. This study has found that the interference effects of the sail on the hull forces, the downforce ahead of the sail trailing edge, and the interaction of individual vortex structures have a significant effect on the total forces experienced by the submarine. By incorporating these results in the existing force model, the maneuverability of submarines with sails could be better predicted, contributing to the safe operation of these underwater vehicles.Item Analysis of a cycloidal wave energy converter using unsteady Reynolds averaged Navier-Stokes simulation(University of New Brunswick, 2014) Caskey, Christopher J.; Jeans, TigerA computational fluid dynamic study was completed to investigate the two-dimensional wave generation and cancellation characteristics of the Atargis Cycloidal Wave Energy Converter (CycWEC). The numerical modeling was based on the unsteady Reynolds average Navier Stokes (URANS) equations and determined the free surface fluctuations using the volume of fluid method. A specialized hybrid grid design was required to accurately resolve the complex viscous flow field resulting from one or more hydrofoils rotating beneath the free surface at a constant angular velocity. The research progressed incrementally from single and two-hydrofoil wave generation concluded with two-hydrofoil wave cancellation. Unlike previous inviscid simulations, the URANS simulations were able to model nonlinear free surface interactions and viscous effects, allowing shaft torques to be numerically predicted for first time. It also provided complete velocity and pressure fields which previous experimental work could not. A grid refinement and time step sensitivity study are completed to increase simulation accuracy and computational efficiency. Fluctuations of wave height, surface pressure distribution, hydrodynamic force, and device efficiency from generated and cancelled wave fields are examined in detail for various hydrofoil pitch angles. For two-hydrofoil wave generation with large pitch angles URANS simulations predicted 94% of the required shaft power is transferred directly to the generated wave field. When operated as an energy extraction device the URANS simulations predicted that up to 92% of the incident wave field was cancelled and 82.7% of the average incident wave power was converted to useful shaft power.Item Computational analysis of the free surface effects on a BB2 submarine undergoing horizontal maneuvers(University of New Brunswick, 2018) Torunski, Brodie; Gerber, Andrew; Jeans, TigerItem Design of fairings for an underwater robot(University of New Brunswick, 2016) Chen, Wenliang; Nabuurs, John; Taylor, Jacob; Jeans, TigerDefence Research and Development Canada (DRDC) Atlantic is having a one-half scale prototype of a large 3 degree of freedom robot built, which is designed to be mounted on the hull of Victoria Class submarines. This robot has a manipulator arm to aid in the deployment and recovery of Autonomous Underwater Vehicles (AUVs). This report presents the complete design and construction procedures for the fairings for the underwater manipulator. The objective of this design is to reduce the drag on the robotic arm by implementing a fairing that covers both the retractable portion of the arm and the arm manipulator mechanism. A final design alone with manufacturing and construction procedures are presented so that the design may be built in the future. A CFD analysis of the self-aligning fairing was performed, in which preliminary results were obtained. The accuracy of these could be achieved through mesh refinement to improve the solution at the boundary layer. A nine time reduction in drag was achieved when the robotic arm is stationary versus the non-faired version of the robotic arm. The goal of zero net lift was not met. Recommendations are provided on how a version of this design could be built that would produce no net lift. Keywords: Fairing, Design, Autonomous Underwater Vehicle, Underwater Robot, Submarine, Self-aligning, Hydrofoil.Item Dynamic model development and simulation of an autonomous active AUV docking device using a mechanically actuated mechanism to recover AUVs to a submerged slowly moving submarine in waves(University of New Brunswick, 2014) Gillis, Colin; Carretero, Juan; Dubay, Rickey; Jeans, Tiger; Watt, GeorgeAutonomous Underwater Vehicles (AUVs) are presenting an ever expanding range of applications that enhance human capabilities and mitigate human risk. Development of a successful subsurface autonomous launch and recovery system would expand the functional use of AUVs in many fields. Defence Research and Development Canada (DRDC) is leading a collaborative project with the University of New Brunswick (UNB) to develop such a system that would recover AUVs to a slowly moving submerged submarine. This thesis provides an overview of the design, dynamic modelling, and preliminary control in simulation of an electro-mechanically actuated AUV dock concept, which operates without using hydrodynamic fluid power to provide motive force. The device is partially faired and has a R⊥R⊥P serial manipulator architecture. In short, the device is referred to as the mechanically actuated RRP serial manipulator. High speed actuation of the device is required to compensate for relative trajectory errors between the submarine and AUV during significant sea states in littoral waters. Hydrodynamic forces present in water cannot be ignored and will be modelled using the Morison Equation. Unimodal Linear Wave Theory is used to simulate AUV kinematics, establishing end effector design trajectories, as well as providing wave kinematics for hydrodynamic modelling. Alterations to the recursive Newton-Euler derivation of manipulator dynamics are explained, and results of simulations are presented. Model Predictive Control (MPC) of the mechanically actuated RRP serial manipulator is simulated using a Dynamic Matrix Control (DMC) architecture. The dynamic models are verified analytically and provide accurate evaluation without lose of generality. Dynamic modelling shows the actuator loads for the proposed device are significant. Drag is the largest contributer and indicates the device must be streamlined. The link diameter used for simulation is overly conservative and should be optimized to reduce its size, this will decrease the required actuator loads. The control simulation shows the DMC controller is a robust design for tracking, however it needs to be combined in a cascading architecture to control both position and velocity for precise control. Overall, the mechanically actuated RRP serial manipulator is a viable design but requires further modelling and development. The device becomes more promising as it is streamlined and reduced in overall length.Item Dynamic modelling and control of an active autonomous wing dock for subsurface recovery of AUVs(University of New Brunswick, 2015) Currie, Jason; Carretero, Juan; Dubay, Rickey; Jeans, Tiger; Watt, GeorgeThe development of robust autonomous launch and recovery (L&R) capabilities for autonomous underwater vehicles (AUVs) would allow a massive broadening of AUV mission scope in all fields. As proposed by Defence Research and Development Canada (DRDC) Atlantic, this project is concerned with the creation of an active third-body autonomous docking system for recovery of AUVs to submerged submarines. This thesis defines the concept of a hydrodynamically actuated wing dock as one solution, and presents the research objectives and methods surrounding its analysis. The wing dock will employ active pitch control to produce lift for motion of the docking system. The recursive Newton-Euler equations of motion typical of manipulator kinematics are used to describe the wing dock. The procedure is modified to account for hydrodynamic forces and a passive rotational joint. A new model for hydrodynamic force distribution is developed to account for asymmetric lift distributions present during docking operations. A model predictive controller (MPC) is also proposed to handle the non-linear, state dependant responses of the end effector to pitch input. Instrumentation of an existing small-scale, partial fidelity prototype was improved and calibrated for testing conducted at DRDC’s Dartmouth facilities. Collected data supports the developed hydrodynamic force models, and confirms a wing is capable of the required end effector trajectories while under motion control by an MPC. Further data is available for validation of the developed forward dynamic simulations once they are complete. The current state of these simulations, recommendations for future work, and some performance observations conclude this thesis.Item Experimental investigation of Canadian East and West Coast fish farm hydrodynamic wake properties and its implications for Integrated Multi-Trophic Aquaculture(University of New Brunswick, 2015) Turner, Adam; Jeans, Tiger; Reid, GregorThe objective of this research was to determine the hydrodynamic properties of salmon cage arrays. Drag and wake properties of aquaculture cage arrays have been studied to further understand the movement of released nutrients from cages as a means to improve Integrated Multi-Trophic Aquaculture (IMTA) performance. Experiments have taken place with 1:15 scale model arrays (2x3) of both circular cages typically used on the East Coast of Canada, and square cages typically used on the West Coast of Canada. The models were deployed for experimentation at the large recirculating flume tank, located at the Fisheries and Marine Institute of Memorial University in St. Johns, Newfoundland. Drag measurements were completed for individual cages within the array with respect to current velocity. Results show the highest drag for the first row of cages, with drag reducing significantly through rows two and three. A wake velocity study behind individual cages within the array and in the wake of the entire array was completed to observe velocity deficits, wake topology, wake recovery and turbulence in the flow field. Results show high velocity deficits directly behind cages within the array, causing flow to be accelerated around and below the cages. The presence of a shear layer in the wake of the cages is observed to cause high levels of turbulence downstream. Finally, dye release was used as a tool to visualize the large scale topology of the flow field and help confirm measured results.Item Hydrodynamic loads on axisymmetric bodies with casings in translation(University of New Brunswick, 2017) Marshall, Cory Robert; Jeans, Tiger; Holloway, Gordon; Watt, GeorgeA comprehensive study was performed of hydrodynamic forces and moments on submarine hull geometries with casings in steady translation using an enhanced database consisting of experimental and computational results. The objective was to develop a hydrodynamic load estimation method that allows for the rapid simulation of the performance characteristics of underwater vehicles. This is an important step in determining the safe operating envelope of submarines. Accurate potential flow and viscous flow results of the geometries of interest were performed at varying incidence and orientation angles. The simulations were verified by a mesh refinement study and validated against analytical solutions and experimental data. Potential flow was found to be a useful predictor of the effects of geometric asymmetric on the out-of-plane and in-plane force distributions and moments. The viscous simulations showed that casings, and hull asymmetries in general, have significant effects on the separation lines, surface pressure distributions, and wake topologies. These effects caused large variations in the in-plane loads and introduced out-of-plane loads. Increasing the casing width produced the largest changes in the in-plane and out-of-plane loads and wake topology. Previous models were found to be unsuitable for the prediction of the in-plane loads on hulls with casings mainly due to their reliance on slender body theory. An alternative model was developed, which combined potential flow with viscous contributions to obtain the hydrodynamic impulse. The tail plane impulse, and therefore the hydrodynamic force, could be approximated with the first nine Fourier modes of the orientation angle. The hydrodynamic moment predictions were found to be accurate. The model was found to have difficulty in predicting the in-plane moment for small asymmetries such as a narrow casing.Item Micro air vehicle design(University of New Brunswick, 2015) Davis, Matthew; Small, Mitchell; Tong, Matthew; Jeans, Tiger; Losier, YvesItem Modelling unresolved bathymetry in tidal flow simulations(University of New Brunswick, 2014) John, Stanley; Jeans, Tiger; Gerber, AndrewInstallation of a tidal turbine at a site requires detailed information of the bathymetry and the surrounding flow field for its deployment and efficient operation. Increasingly, Computational Fluid Dynamics (CFD) is being used to predict the local unsteady flow field. Bathymetry data is generally of a different resolution than required for CFD meshing, and requires special treatment for incorporation into the meshing process. This process results in resolved and unresolved bathymetry features that may be important in obtaining accurate CFD predictions. This issue is explored at a tidal site located in Minas Passage which connects the Minas Basin to the Bay of Fundy. Bathymetry processing is considered in conjunction with a high resolution Detached Eddy Simulation (DES) of turbulent tidal flow obtained using a 26 million node mesh. This particular site has a steep ridge which results in significantly large unresolved data relative to the mesh size, specifically at the ridge. A methodology is suggested to separate the unresolved data into sub grid and supra grid scales. The sub grid data is modelled using the sand grain roughness model while supra grid data is modelled using the proposed form drag model. Predicted results are compared to Acoustic Doppler Current Profiler (ADCP) measurements for one tidal site under ebb conditions for an inlet velocity of 4 m/s. The improved model gives results closer to the experimental data as compared to the sand grain roughness model.Item NACA wing design(University of New Brunswick, 2015) MacArthur, Jesse; Uzoanya, Chimezirim; Young, Jonathan; Jeans, TigerItem Numerical investigation of leading edge radio effects on MULDICON flow characteristics(University of New Brunswick, 2017) Maye, Ryan, Gregory; Jeans, TigerItem Numerical simulation of ducted and non-ducted tidal turbines using actuator line method(University of New Brunswick, 2018) Baratchi, Farhad; Jeans, Tiger; Gerber, AndrewElectricity generation using tidal turbines is a relatively new technology in the renewable energy field. These turbines, due to their harsh and complex operational environment, must be engineered to operate with low maintenance and high efficiency. Therefore, significant research and development is being undertaken to achieve these operational goals, and high fidelity numerical tools such as CFD are being applied to the problem. However, tidal flows are very site-specific and only in-situ simulations can give a reliable estimate of a turbine's performance and the imposed forces on its components. In this thesis, the actuator line (AL) method is investigated as a method feasible for in-situ simulation of tidal turbines in high resolution CFD simulations. The AL method does not require a detailed treatment of the turbine blade geometry but incorporates its rotational effects on the flow. It therefore becomes more computationally efficient while also maintaining the ability to include dynamic loads and wakes. Therefore, in this work the AL method has been developed in a heterogeneous CPU/GPU parallel architecture and its implementation has been validated by simulating a well-studied non-ducted tidal turbine at different tip speed ratios (TSRs) in straight and yawed flows and investigating the turbine's parameters and wake. Next, considering the popularity of the ducted design in tidal turbines, and the fact that presently there appears to be no study on applying the AL method to ducted turbines, an important goal of this work has been to extend the AL method for simulations of ducted turbines. This has been done by investigating two ducted tidal turbines and revising the method based on the unique features of ducted turbines. This in particular includes using the grid-based distribution of blade elements and the cylindrical projection of the imposed force on each blade element. Improving the projection process by using the local chord length as the length scale for the projection factor and providing a guideline for choosing this factor have also been carried out. This thesis also includes comprehensive discussions on generated wakes and predicted power and thrust coefficients for these two turbines in different conditions.Item Predicting the transient hydrodynamic loads on submarine hulls in unsteady maneuvers(University of New Brunswick, 2020) Doyle, Robert Andrew; Jeans, Tiger; Holloway, GordonSubmarine maneuvering analysis requires accurate and computationally efficient methods to predict the hydrodynamic loading on a vehicle. During maneuvers in a viscous fluid, this loading will have unsteady contributions from both the added mass of the surrounding fluid, and from motion history effects due to the shedding of vorticity into the wake. Despite this, the majority of models for submarine hydrodynamics assume quasi-steady loading, which neglects the motion history effect. This assumption is primarily made due to our limited understanding of unsteady submarine hydrodynamics. This work presents an analysis of the flow around unappended, maneuvering submarine hulls. This was accomplished using Computational Fluid Dynamics simulations of the flow around the hull. These simulations were validated by comparison against experimental data for an Unmanned Underwater Vehicle of similar geometry to a submarine hull. A range of maneuvers were simulated to explore the effect of unsteady motion. These maneuvers were restricted to planar motions without rotation, and included steady translations, impulsive accelerations, sustained accelerations, and sinusoidally oscillating maneuvers. The hulls studied range in slenderness from 7.5 < l/D < 9.5, with a Reynolds number of Re = 3.14e6 and reduced frequencies from k = f l/2U = 0.01 to k = 0.3. Motion history effects were seen to vary in significance with reduced frequency, and have a maximum impact at moderate values of 0.12 < k < 0.2. This analysis was conducted using both classical techniques and modern vorticity based methods. It was demonstrated that the vorticity based analysis allows for the decomposition of unsteady forces without the need for external data. A slender body approximation of the vorticity based description was developed and demonstrated to have good accuracy for all cases. An existing quasi-steady force estimation model was extended to include unsteady motion. This model used indicial function theory and the vortex-based force description. The unsteady model improved predictions relative to the quasi-steady assumption for reduced frequencies above k ≈ 0.1, but significantly increased the computational cost.Item Simulation and force modeling for a submarine with a hull + sail configuration in a steady turn(University of New Brunswick, 2023-03) Farooq, Ahmed; Jeans, TigerThe effect of turning on a submarine in a hull and sail (H+S) configuration is investigated by RANS based numerical simulations at a fixed Reynolds number of 23×10 6 . The two geometric parameters in the problem are (i) the turning ratio, given by R/ℓ, where R is the turning radius of the hull center of buoyancy and ℓ is the hull length. The turning ratio is varied from 1 to 10 covering a full range of turns from very tight ones where the submarine turns within a hull length to ten times hull length (which can also be seen to be an asymptotic approximation of ∼ ∞). (ii) the pivot point of the submarine is assumed to be at λp/ℓ = 0.25 where λp is the distance of the pivot point from the nose of the submarine. Kinematic constraints fix the yaw angle for the center of buoyancy for a given turning ratio (the local yaw angle varies along the hull length for a submarine in a turn). The resulting forces and moments which include both in-plane yaw forces and also out-of-plane pitch forces are obtained and compared to the analytical models used in DSSP, (see Mackay [43]) showing fair agreement. In general, it has been found that the axial drag force, the yaw force and the pitch forces increase with the tightness of the turn. However, the behavior of the moments is more complex and while the roll moment increases monotonically with the tightness of the turn, the pitch and yaw moments show an initial increase and then fall as the turn is made tighter with a peak at R/ℓ ∼ 1.5. Parametric studies have been run to investigate the effect of sail height Sh/ℓ and the pivot point location λp/ℓ. A reduced sail height, predictably, reduces the yaw force and moment. The effect of pivot point position is more complicated because as it approaches the center of buoyancy, the entire sail experiences negative incidence resulting in a reversal of the direction of the yaw force on the sail.Item Simulation, design, and analysis of the hybrid magnetic attitude and thermal control systems for the violet nanosatellite mission(University of New Brunswick, 2021-11) DiTommaso, Alexander Maurice Pietro; Jeans, Tiger; Petersen, BrentDue to the accelerating growth of the nanosatellite industry, there is a gap to fill for more innovative, cost-effective attitude and thermal control solutions. Passive Magnetic Attitude Control (PMAC) systems are capable of aligning a spacecraft within ten degrees of the local geomagnetic field vector and have minimal mechanical complexity. The VIOLET CubeSat (2U), requires a solution with more pointing options due to the area of the ionosphere to be imaged by the Spectral Airglow Structure Imager (SASI) payload. A novel and cost-effective solution has been developed, named the Hybrid Magnetic Attitude Control (HMAC) system. This system utilizes PMAC components with the addition of five air-core magnetic torque coils aligned with the body-fixed axes of the nanosatellite. The attitude dynamics of VIOLET are simulated by the Smart Nanosatellite Attitude Propogator (SNAP) Simulink® tool box, which all relevant environmental and orbital conditions are considered. VIOLET is unique in the fact that it is a 2U, dual payload nanosatellite with an unusually high thermal output of its communications system. The small form factor coupled with high thermal output is a critical problem to solve to achieve mission success. Siemens NX Space Systems Thermal is being utilized to create a Finite Element Model (FEA) to properly model the thermal behavior of the nanosatellite for both Worst Case Hot (WCH) and Worst Case Cold (WCC) scenarios. The design of the Thermal Control System (TCS) progressed concurrently with the analyses to define heat paths throughout VIOLET, to ensure sub-system components will not exceed their acceptable temperature ranges.Item The effect of wing tip blowing on the spanwise pressure distribution at the University of New Brunswick(University of New Brunswick, 2001) Jeans, Tiger; G., Holloway