Supercavitating motion of a wedge in a jet

The problem of determining the free surface of a jet incident on a rigid wedge and the bound- ary of a cavity behind the wedge is considered. The single- and double-spiral-vortex models by Tulin are used to describe the flow at the rear part of the cavity. The location of the wedge in the jet and the sides lengths are arbitrary. This circumstance makes the flow domain doubly connected for the single-vortex model whilst it is simple connected for the double-vortex model. Both the models are solved in closed form by the method of conformal mappings. The maps are expressed through the solutions to certain Riemann-Hilbert problems. For the former model, this problem is formulated on a genus-1 Riemann surface. The double-vortex model requires the solution to a standard Riemann-Hilbert problem on a plane. It is found that the drag and lift are practically the same whilst the jet surface, the cavity boundary at the rear part and the deflection angle of the jet at infinity are different. Also, the problem of determining the parameters for the conformal mapping in the singlevortex model has two solutions. It is shown that one of the solutions leads to a non-physical shape of the cavity and needs to be discarded. The case of a wedge in a channel with a free surface is also analyzed.http://deepblue.lib.umich.edu/bitstream/2027.42/84229/1/CAV2009-final21.pd

Method of Riemann surfaces in modelling of cavitating flow

This dissertation is concerned with the applications of the Riemann-Hilbert problem on a hyperelliptic Riemann surface to problems on supercavitating flows of a liquid around objects. For a two-dimensional steady irrotational flow of liquid it is possible to introduce a complex potential w(z) which allows to apply the powerful methods of complex analysis to the solution of fluid mechanics problems. In this work problems on supercavitating flows of a liquid around one or two wedges have been stated. The Tulin single-spiral-vortex model is employed as a cavity closure condition. The flow domain is transformed into an auxiliary domain with known boundaries using the conformal mapping method. After that the problems have been reduced to the solution of Riemann-Hilbert problems on elliptic or hyperelliptic Riemann surfaces. The final step is to solve a system of transcendental equations which is accomplished numerically. The numerical results are presented. To the best of the author’s knowledge no numerical results were available for non-linear problems on supercavitating flows in multiply connected domains before

Modelling, testing and design, of a surface piercing propeller drive

In collaboration with Marinetech South Ltd., Defence, Evaluation and Research Agency, Haslar and Teignbridge Propellers Ltd.Available from British Library Document Supply Centre-DSC:DXN036584 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

The Hydrodynamic and Hydroelastic Responses of Rigid and Flexible Surface-Piercing Hydrofoils in Multi-Phase Flows

Ventilation and vaporous cavitation are multi-phase flows with critical effects upon the performance, stability, and controllability of high-speed marine vessels. The entrainment of air from the free surface (ventilation) or the formation of water-vapor-filled voids (cavitation) can cause dramatic reductions in the efficiency of lifting surfaces, large dynamic loads, and strongly hysteretic flows. This thesis investigates the hydrodynamic and hydroelastic performance of surface-piercing hydrofoils through experiments on three hydrofoil models (one rigid and two flexible), which were tested in a towing tank and in a free-surface cavitation tunnel. The results reveal four distinct flow regimes, which are defined by their parametric stability regions. The concept of flow stability is used to describe transitional flow and resulting hysteresis to yield a holistic description of ventilation on surface piercing hydrofoils. These concepts are used to develop scaling relations for the washout of ventilated cavities. Hydrodynamic loads are shown to vary as functions of the attack angle, immersion depth, forward speed, cavitation number, and flow regime. Flexibility of the hydrofoil model modifies the hydrodynamic loads and stability regions through hydroelastic coupling. Flow-induced vibration and lock-in are shown to result from coherent vortex shedding at all speeds tested. Fitted transfer functions are used to develop reduced-order models and to estimate modal parameters of a flexible hydrofoil, demonstrating that both modal resonance frequencies and modal damping ratios are dependent upon immersion depth, forward speed, and flow regime. A robust shape-sensing strut is also developed to measure the textit{in-situ} structural motions of deformable lifting-surfaces in real time. The work presented in this thesis contributes significantly toward the study of multi-phase flows and fluid-structure interactions through the establishment of experimental methodologies, the construction of a versatile experimental platform with original instrumentation, and the collection and thorough interpretation of a large, rich dataset. The insights gained from the work significantly improve our understanding of ventilation, cavitation, and their interactions with structural dynamics, thereby aiding future researchers and designers to perform robust experiments, validate numerical solvers, and design safe, efficient, and controllable marine devices.PHDNaval Architecture & Marine EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/135891/1/cmharwoo_1.pd

A cumulative index to Aeronautical Engineering: A special bibliography, January 1976

This publication is a cumulative index to the abstracts contained in NASA SP-7037 (54) through NASA SP-7037 (65) of Aeronautical Engineering: A Special Bibliography. NASA SP-7037 and its supplements have been compiled through the cooperative efforts of the American Institute of Aeronautics and Astronautics (AIAA) and the National Aeronautics and Space Administration (NASA). This cumulative index includes subject, personal author, corporate source, contract, and report number indexes

Aeronautical Engineering: A special bibliography with indexes, Supplement 35, September 1973

This special bibliography lists 614 reports, articles, and other documents introduced into the NASA scientific and technical information system in August 1973

A cumulative index to Aeronautical Engineering: A special bibliography, January 1975

A cumulative index to the abstracts contained in NASA SP-7307 (41) through NASA SP-7037 (52) is presented. Subject, personal author, corporate source, contract, and report number indexes are included

Large sailing ships : a fluid dynamic investigation

Imperial Users onl