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Thesis: Nav. E., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017., Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017., Cataloged from PDF version of thesis., Includes bibliographical references (pages 49-50)., The fluid-dynamic design of hydrofoils to support marine crafts at high speeds has received growing interest in recent years. Physics involved in the design of high-speed surface-piercing hydrofoils is complex involving three different fluid phases (air, water and vapor) and complex fluid dynamic mechanisms like unsteady cavitation and ventilation and their interaction. For speeds considerably higher than the incipient cavitation speed, the hydrofoil sections need to be adapted and design to exploit cavitation instead of avoiding it. This is particularly true for surface piercing hydrofoils that in addition to cavitation are affected by ventilation from the free surface. This thesis presents main results of an investigation into the relative formation of ventilation and cavitation regions of surface piercing super cavitating hydrofoils (SPSCHs), with special attention to the effects of cavitation number. A series of 3D multi-phase Reynold Averaged Navier-Stokes Equation (RANSE) simulations of varying cavitation number reveal the dependence of the ventilation and cavitation regions on the cavitation number, angle of attack, and distance from the free surface. The RANSE simulations are validated against an analytical estimate based on an appropriate lifting line method at near zero cavitation numbers, and against empirical results obtained through tow tank testing at higher cavitation numbers. The analytical and empirical validation bound the range of cavitation numbers considered in this study from [sigma]= 0.05 to [sigma]= 2.37., by Timothy Spaulding Dutton., Nav. E., S.M.

Thesis: Nav. E., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018., Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018., Cataloged from PDF version of thesis., Includes bibliographical references (pages 99-100)., Computer automated design of complex physical systems is often limited by the computational resources required for the high precision solvers. Determining an optimum design necessitates high accuracy simulations due to the multi-dimensional design space and the interconnectedness of the constraint and objective quantities. This paper will present an automated framework for iterating through a design loop that includes both physics-based computer simulations and surrogate model training using machine learning techniques. To alleviate the computation burden and efficiently explore the design space, a surrogate model for each quantity of interest that cannot be found deterministically will be utilized. Further reduction of the computational cost is accomplished by utilizing both low- and high-fidelity data to build the response surfaces. These response surface models will be trained using multi-fidelity Gaussian process regression. The models will be iteratively improved using Bayesian optimization and additional high-fidelity simulations that are automatically initiated within the design loop. In addition, Bayesian optimization will be used to automatically determine the optimum kernel for the Gaussian regression model. The feasibility of this framework is demonstrated by designing a 2D super-cavitating hydrofoil and comparing the optimum shape found with a known benchmark design. This automated multi-fidelity Bayesian optimization framework can aid in taking the human out of the design loop, thus freeing manpower resources and removing potential human bias., by Benjamin W. Parker., Nav. E., S.M.

Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017., Cataloged from PDF version of thesis., Includes bibliographical references (page 17)., Flapping foils were tested to produce large, transient forces in still water. These swift, onetime strokes take advantage of added mass/inertial effects and large, stably attached vortices to avoid delay due to the realization of a jet wake for propulsion [1]. Previous work has produced trajectories, characterized by heave and pitch, for which the lift and thrust profiles were confirmed. Two trajectories were reproductions from previous studies, and the lift and thrust force profiles match those produced before. An additional trajectory was tested, which produced a much different profile. All three trajectories included a smooth sweeping motion, but the third trajectory included a subsequent sharp change in pitch. This sharp change in pitch, or pure rotation, produced sharp force peaks and oscillations in thrust, in addition to force peaks from the sweeping motion which resembled the other two trajectories' profiles. Further work includes confirming the lift and thrust coefficients and exploring additional trajectories or optimizing current trajectories for producing large, transient forces for underwater vehicle propulsion and control., by Miranda Kotidis., S.B.

Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017., Cataloged from PDF version of thesis., Includes bibliographical references (page 39)., Flapping foils are the standard engineering approximation for many biological actuators in air and water, but these devices typically provide propulsion at the cost of parasitic oscillatory forces. The addition of in-line motion to a flapping foil trajectory can improve the control of the fluid force. Previous work has shown that by actuating the heave, surge, and pitch motions of a foil and iteratively optimizing the results, the lift and thrust forces on the foil can be precisely and independently controlled. In this thesis, the same experiment is modified to include solely passive pitch to determine if similar force control performance can be achieved without either a fully actuated pitch motion or an optimization process. In the new experiment, the fluid forces naturally drive the pitch motion for most of the flapping cycle, until the foil reaches a maximum pitch angle, which is set with a mechanical stopper. The hydrodynamic forces are recorded for a range of trajectories that include forwards in-line, backwards in-line, and no in-line motion. Lift force control improves over that of the fully actuated system, but thrust force control is not achieved to the same level of performance. Further work can be done to determine whether simple pitch angle control can be implemented to improve thrust force control without the addition of the optimization process., by Fiona Grant., S.B.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016., Cataloged from PDF version of thesis., Includes bibliographical references (pages 277-284)., The performance of marine vehicles is largely influenced by interactions with the flow around their hull, both self-generated and environmentally driven. To improve performance through flow control, a detailed, real-time measurement of the near-field flow is necessary, yet such sensing capability is presently unavailable. Looking to nature for inspiration, fish employ the distributed pressure and velocity sensing capability of their lateral line sensory organ to mediate navigation and control behaviors that, if replicated, could benefit engineered systems. Through a series of towing tank and field experiments, it was found that while distributed pressure measurements on marine vehicles enabled the detection of near-body flow phenomena, the size, cost, and mounting requirements of commercial sensors lead to sparse arrays and substantial gaps in the characterization of the flow field. To address the challenges associated with obtaining spatially-dense pressure measurements on curved surfaces in marine environments, a new waterproof and conformal pressure sensor array was developed based on a closed-cell piezo resistive foam composed of carbon black-doped-silicone composite (CBPDMS foam). The response of the CBPDMS foam sensor arrays was characterized using periodic hydrodynamic pressure stimuli from vertical plunging and water waves, and a piecewise polynomial calibration was developed to describe the sensor response. The sensitivity and frequency response of the sensor arrays was also documented through a series of biologically-inspired hydrodynamic stimuli, including the flow from a dipole source, and the Karmin vortical wake flow behind a circular cylinder. The CBPDMS foam sensor arrays have significant advantages over existing commercial sensors for distributed flow reconstruction and control. They are found to have sensitivity on the order of 5 Pascal, frequency range of 0.5-35 Hertz, are contained in a waterproof and completely flexible package, and have materia, by Jeff Ernest Dusek., Ph. D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2001., Includes bibliographical references (leaves 147-153)., by Georgios Papaioannou., S.M.

Thesis: M.B.A., Massachusetts Institute of Technology, Sloan School of Management, 2014. In conjunction with the Leaders for Global Operations Program at MIT., Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014. In conjunction with the Leaders for Global Operations Program at MIT., Cataloged from PDF version of thesis., Includes bibliographical references (page 77)., A pragmatic approach is taken at analyzing and improving Sales and Operations Planning in a project based, engineer-to-order product line. Variability of product and components configurations and long lead times of the sales process and of material procurement during project execution place additional planning challenges in comparison with a standardized high volume product business. The study focuses on improving the visibility on future customer orders and on reducing the procurement lead time of project material. Due to the nature of the market and the customers of the studied product line, incoming orders timing is very uncertain when viewed on a project by project basis. However, there is a specific dynamic when the sales pipeline is analyzed on aggregate: Tenders that end up converting into a customer order will do so sooner rather than later. Historical data and observations are used to develop and propose a probabilistic model that connects today's open tenders to the expected new business out of those tenders. The organization is able to use this model to estimate what the current activity of the sales force can produce in terms of new business. The expected benefit is that the organization can act proactively if there is an expected reduction in incoming business from a specific region or major customer; it can also make targeted efforts to increase sales activity towards that region or customer. To increase its competitiveness when bidding for new projects, the organization has embarked on an effort to reduce the overall project execution lead time. A significant portion of this lead time is waiting time for project specific material (which comprises the biggest part of the BOM in money terms). A supplier flexibility scheme is proposed, under which a material order is placed in two phases: first the desired delivery time and the component rough specification are specified, and later on the exact specs are given to the supplier. An optimization model that, by Andreas Christogiannis., M.B.A., S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010., Cataloged from PDF version of thesis., Includes bibliographical references (p. 126-132)., This Masters thesis, conducted in support of the All Electric Ship (AES) early design effort, presents two computational programs for analysis and simulation: a full-scale, end-to-end AES simulator and an analytical performance and stability assessment tool for the ship's propulsion drive; the integrated power system (IPS). The AES simulator incorporates high order techniques for the hull modeling with low order, low effort models for the propellers, IPS, and prime movers, culminating in a fully-coupled, end-to-end, simulation environment, which is still practical for high effort studies like uncertainty quantification or optimization. The most appealing characteristic of this program is the time domain hull model with combines nonlinear maneuvering equations, seakeeping equations, and second order wave force equations. This allows for the prediction of propeller elevation and inflow velocity in random seas, and effectively the high fidelity modeling of propeller load schedules. This capability is vital for AES design where propeller load fluctuations can lead to large electrical power transients onboard. To demonstrate the capability of the AES simulator, ship trails are run in calm and random seas. IPS state evolutions are given to show the propagation of load disturbances. Monte Carlo methods are applied to assess transients in the inherently random sea environment. The IPS assessment tool attempts analytical quantification of the performance and stability of the Purdue MVDC Testbed, a scaled IPS composed of analagous elements: electric machinery, power converters, MVDC distribution, and bus voltage/induction motor torque control schemes. The thesis details the applicable nonlinear equations and the tools for identifying system equilibrium points. Then, small displacement theory is used to attain linear state space matrices valid near the operating points, from which traditional stability and performance techniques can be applied. Methods for closed loop analysis, by Kyle Schmitt., S.M.

Includes bibliographical references (p. 211-216)., Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and the Woods Hole Oceanographic Institution), 2008., Inspired by the swimming abilities of marine animals, this thesis presents "Finnegan the RoboTurtle", an autonomous underwater vehicle (AUV) powered entirely by four flapping foils. Biomimetic actuation is shown to produce dramatic improvements in AUV maneuvering at cruising speeds, while simultaneously allowing for agility at low speeds. Using control algorithms linear in the modified Rodrigues parameters to support large angle maneuvers, the vehicle is successfully controlled in banked and twisting turns, exceeding the best reported AUV turning performance by more than a factor of two; a minimum turning radius of 0.7BL, and the ability to avoid walls detected > 1.8BL ahead, are found for cruising speeds of 0.75BL/s, with a maximum heading rate of 400/s recorded. Observations of "Myrtle", a 250kg Green sea turtle (Chelonia mydas) at the New England Aquarium, are detailed; along with steady swimming, Myrtle is observed performing 1800 level turns and rapidly actuating pitch to control depth and speed. Limb kinematics for the level turning maneuver are replicated by Finnegan, and turning rates comparable to those of the turtle are achieved. Foil kinematics which produce approximately sinusoidal nominal angle of attack trace are shown to improve turning performance by as much as 25%; the effect is achieved despite limited knowledge of the flow field. Finally, tests with a single foil are used to demonstrate that biomimetically inspired inline motion can allow oscillating foils utilizing a power/recovery style stroke to generate as much as 90% of the thrust from a power/power stroke style motion., by Stephen Carl Licht., Ph.D.

Thesis (S.M. in Naval Architecture and Marine Engineering; and, S.M. in Ocean Systems Management)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, June 2007., "May 2007.", Includes bibliographical references (p. 51)., Vortex Induced Vibrations (VIV) is a major concern of the offshore oil industry. This problem leads to fatigue failure in the marine risers and causes costly replacement of the risers. Appendages such as helical strakes have proven that VIV can be eliminated but at the cost of increased drag. Increased drag reduces the time that the riser can operate. This thesis looks at adding airfoils to cylinders to both eliminate VIV as well as reducing drag. Two sets of tests were performed at the MIT Towing Tank to determine the effectiveness of these airfoils. The first tests utilized a flexible to model a riser. The second set of tests used a rigid cylinder to better understand the dynamics of the system. The airfoils were able to achieve both goals when the airfoils are aligned with the flow. Future work needs to be completed to study the airfoils when they are not aligned with the flow., by Evan J. Lee., S.M.in Naval Architecture and Marine Engineering; and, S.M.in Ocean Systems Management

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007., Includes bibliographical references (p. 73-75)., Unmanned underwater vehicles have various missions within civilian, military and academic sectors. They have the ability to explore areas unavailable to manned assets and to perform duties that are risky to humans. In particular, UUVs have the ability to perform bearings-only tracking in shallow areas near shorelines. This thesis presents a guidance algorithm for this particular mission. This thesis first presents a Modified Polar Extended Kalman Filter for the estimation problem. Bearings-only tracking is a nonlinear problem that requires some sort of estimator to determine the target state. The guidance algorithm is developed based on the relative positions of the observer and the target. In order to develop the guidance algorithm, the effectiveness of a variety of course maneuvers are presented. The effectiveness of these maneuvers are analyzed both quantitatively and qualitatively. The results from this analysis is incorporated into the final guidance algorithm. This thesis also evaluates the developed guidance algorithm through a series of simulation experiments. The experiments explore a variety of scenarios by varying speed, geometry and acoustic environment. The results of the experiments are analyzed based on estimation errors and detection time. The final conclusions indicate that some of the geometries are more favorable than others. In addition, the degree of noise in the acoustic environment affects the range of the UUV's sensors and the UUV's ability to perform bearings-only tracking for an extended period of time. In addition, the desired speed ratio is one in which the observer is either the same speed as or slower than the target., by Danica Lee Middlebrook., S.M.

Thesis (S.M. in Naval Architecture and Marine Engineering ; and, S.M. in Ocean Systems Management)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006., Includes bibliographical references (leaves 54-55)., The M.I.T. Towing Tank has served as an invaluable research and educational platform for over 50 years. The hands-on learning experiences of towing tank tests have helped countless students to grasp the concepts and theories that are taught in the classroom environment. A recent upgrade of the M.I.T. Towing Tank increased the accuracy and capabilities of the facility, but also provided new capabilities to help create an Internet-based, distance learning tool. This new program has enabled M.I.T. to share its towing tank with students from other schools and universities via the Internet. The educational value of this tool was tested via an online set of experiments, performed by a partnered university, and has demonstrated the many benefits derived by this new capability. The upgrades to the facility have also increased the value of the M.I.T. Towing Tank for educational and commercial research. In recent years, the research interests at M.I.T. have significantly diversified, leading to new demands and capabilities being placed on the towing tank. As a result of the upgrades, the towing tank is now a highly flexible platform, on which a variety of research may be performed., by Matthew L. Unger., S.M.in Naval Architecture and Marine Engineering ; and, S.M.in Ocean Systems Management

Thesis (Nav. E. and S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2004., Leaf 185 blank., Includes bibliographical references (leaves 172-174)., Diesel and gas turbine electric ship propulsion are of current interest for several types of vessels that are important for commercial shipping and for the next generation of war ships. During the design process of a platform, a choice has to be made between two different fundamental concepts regarding propulsion; a conventional arrangement, and a diesel or gas turbine electric propulsion. For both concepts, the electrical installation is present and the demand for additional electric energy becomes a dominant parameter. In both cases, the selection of the prime mover significantly influences the effectiveness of the design. In this thesis, the simulation modeling of a complete propulsion system will be attempted, with overall emphasis on the prime movers. In the first part a diesel engine is considered. The time delay between changing a set point for the revolutions of the engine and the change of the real revolutions is often modeled as a first order system. However, this modeling is too simple to describe the real behavior of the diesel engine. More complex models exist, but in general they are too complex, describing the full thermodynamic behavior of diesels., (cont.) So there is a need for a model that is more advanced than a first order system and less complex than complete thermodynamic models. Such a model has been derived, based on the Seiliger (thermodynamic) process. The results of the model show that the diesel engine behaves like a second order system when operating in the governor area and more like a first order system in the constant torque (overload) area. The simulation model of a diesel engine can be regarded as an explanation of the real engine operation, which combines the mathematical relationship between the relative components and can be used to simulate dynamic loading of the diesel engine. In the second part, a development of a nonlinear gas turbine model for loop- shaping control purposes is presented. The nonlinear dynamic equations of the gas turbine are based on first engineering principles. In order to complete the model, constitutive algebraic equations are also needed. These equations describe the static behavior of the gas turbine at various operating points., (cont.) The complete, substituted nonlinear model is presented along with its model verification results based on a simulator and measured data. A mathematical description for the electric part of the propulsion and energy generation system with respect to numbers of components such as generators and thruster drives is attempted. Other electrical loads may be represented with an aggregate load. Based on the control functions focus on power production, advanced dynamic models shall be used for the generators and simplified static models shall be used for thruster drives and other loads. The final model shall be in a state-space vector form, suitable for control design. As a conclusion, a reliability analysis on the decision for the electric propulsion system is utilized based on market data, speed and electric energy requirements studies. The purpose of this study is to justify the employment of innovative and efficient electric propulsion systems for the future needs of the commercial and naval ship industries., y Charalambos Soultatis., Nav.E.and S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2000., Includes bibliographical references (leaf 66)., Model testing to date has not incorporated the simulation of realistic propulsion in the testing of closed loop control of ships. The development of a DDG-51 hull model for these tests is described, and the preliminary data from the sensor suite to be used for feedback control is analyzed. Based on the short duration of tests, the angular rate sensors are relied upon to correct for gravitational contributions in pitch while stabilized roll is used for sway correction. Signal noise, integration errors and sensor drift are bandpass filtered out in selected sensor channels. The preliminary results of double integrated position in global coordinates correlate well with experimental observations, and recommendations for continued development of the ship model are made., by Albert Wu., S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2004., Includes bibliographical references (v. 2, p. 587-601)., Flow-structure interaction is a generic problem for many engineering applications, such as flow--induced oscillations of marine risers and cables. In this thesis a Direct Numerical Simulation (DNS) approach based on spectral/hp elements is employed. Structural motion implies changes on the boundaries of the flow domain. An Arbitrary Lagrangian Eulerian (ALE) scheme is incorporated to efficiently move the mesh without remeshing. Efficient three-dimensional simulations with periodicity in at least one space direction are achieved using Hybrid Fourier-Jacobi expansions. Both 2D and 3D formulations can treat an arbitrary number of oscillating bodies. Due to the large computational demands of the resulting systems parallel computing is used with MPI. Numerical experiments are run and systematic data sets are obtained for flow around two cylinders. Stationary cylinders in tandem and side-by-side arrangements are examined parametrically over spacing and Reynolds number. Parametric studies of tandem cylinders in prescribed motion and free oscillation are also conducted. For tandem cylinders, sudden changes in the forces occur at a critical spacing where a transition from reattachment to binary vortex regime occurs., (cont.) A hysteresis effect is observed for spacings near the nominal critical, where for given Reynolds number there are two possible solutions depending on the initial conditions. Discrepancies in the prediction of the critical spacing using 2D and 3D simulations are identified and explained. The three-dimensional effects are found to cause a weakening of the strength of the primary vortices and a delay in the inception to) binary vortex regime. When the cylinders oscillate in prescribed motion, the phase angle of the oscillations can alter significantly the hydrodynamic work on the downstream cylinder. For spacings smaller than the critical spacing, the lock-on range of frequencies is wider than that of a single cylinder. As the oscillations amplitude increases however, pockets of non-lock-on regions are found within the Arnold synchronization regions. A shift towards higher frequencies in the synchronization range is found for the in-phase oscillations compared to the anti-phase oscillations. A consistent change is found in the spanwise correlations. For the elastically mounted two-degree of freedom tandem cylinders it is found that the synchronization range of the upstream cylinder is wider when its latest shed pair of vortices intercepts the downstream cylinder., (cont.) A shifting of the synchronization curve on the reduced velocity axis is observed and explained in terms of the natural shedding frequency of the corresponding stationary system of cylinders., by Georgios V. Papaioannou., Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2000., Includes bibliographical references (p. 75-76)., A robotic mechanism is described, called Robopike. The robot has fork length equal to 82cm, and contains 5 motors, a computer and a wireless modem for communication during testing. Details of the construction and testing methods are provided. The testing covered only a small part of the extensive parametric range, and resulted in speeds up to 0.11 body lengths per second and turns of 350 in two seconds. The kinematics of the robot are quantified and analyzed. A non-dimensional number, the Maneuvering Strouhal Number (Stm) is defined based on observations from live fish and previous theoretical developments. Recommendations for further improvements in the maneuvering performance of flexible hull vehicles are derived based on the Maneuvering Strouhal Number (Stm)., by John Muir Kumph., S.M.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1996., Includes bibliographical references (leaf 132)., by John Muir Kumph., B.S.