This paper describes a rigorous design method for supercavitating propellers (SCP). An optimum circulation distribution was calculated by Lerbs' lifting line theory. Lifting surface correction based on a vortex lattice method was directly made by using the most favourable load distribution based on a non-linear supercavitating flow theory. Three SCPs were designed and they all generated the required thrust at the design point except the highly loaded one. The efficiencies were reasonably high for all propellers. It is concluded that the method is one of the most promising and reliable tools for designing high performance SCPs.

A low-order potential based 3-D boundary element method (BEM) is presented for the analysis of unsteady sheet cavitation on supercavitating and surface-piercing propellers. The method has been developed in the past for the prediction of unsteady sheet cavitation for conventional propellers. To allow for the treatment of supercavitating propellers, the method is extended to model the separated flow behind trailing edge with non-zero thickness. For surface-piercing propellers, the negative image method is used, which applies the linearized free surface boundary condition with the infinite Froude number assumption. The method is shown to converge quickly with grid size and time step size. The predicted cavity planforms and propeller loadings also compare well with experimental observations and measurements.

methods

Design of high performance supercavitating propellers based on a vortex lattice method

Analysis of supercavitating and surface-piercing propeller flows via BEM

A 3-D panel method has been extended to model the flow around fully submerged supercavitating propellers and surface-piercing propellers. Overviews of the formulation and solution methodology is presented. Comparisons of the numerical predictions with measurements from experiments are given. Discussion of the numerical results, and initial work on modeling of impact flows are provided.

Numerical Modeling of Supercavitating and Surface-Piercing Propeller Flows

High-speed propulsor blades often experience moderate to substantial amounts of unsteady cavitation, and up to now have been designed via design methods for noncavitating blades combined with methods for the analysis of cavitating flows in a trial-and-error manner. In this thesis a numerical non-linear optimization algorithm is developed for the automated, systematic design of cavitating blades. The objective and constraint functions in the optimization process are expressed in terms of the design variables via linear approximations of the results from an existing lifting-surface analysis method, in the first stage of the algorithm, and quadratic approximations in the final stage. In this way the number of required geometries to be analyzed and the associated computational effort are minimized. The developed methodology is implemented in a modular manner so that future improvements in the modeling of cavitating flows can be readily incorporated. The proposed algorithm is validated with several known non-linear optimization test problems. The method is first applied to the design of efficient two-dimensional partially and supercavitating hydrofoil sections and the results are compared to those from a previously developed optimization procedure. Then, the method is applied to the design of propeller blades in uniform flow. The blade mean camber surface is defined via a cubic B-spline polygon net in order to facilitate the handling of the geometry, and to reduce the number of the design parameters. Non-cavitating blade geometries designed by the present method are directly compared to those designed via an existing lifting-line/lifting-surface design approach. Finally, the optimization algorithm is applied to the design of cavitating blades in non-uniform flow. The objective of the design is to obtain maximum propeller efficiency for given conditions by allowing controlled amounts of sheet cavitation. Several constraints on the unsteady cavity characteristics, such as the area of cavity planform and the amplitudes of the cavity volume velocity harmonics, are incorporated in the optimization technique. The effect of the constraints on the efficiency of the propeller design is demonstrated with various test cases. Thesis Supervisor: Spyros A. Kinnas Title: Assistant Professor Department of Civil Engineering, The University of Texas at Austin Acknowledgments There are a lot of contributions from many people to this thesis work. I first would like to express my greatest possible gratitude to my thesis supervisor, Professor Spyros Kinnas, at the University of Texas at Austin. He has always been encouraging me and giving me invaluable advices in every situation, even on weekends. I got several pieces of email every week from him and I knew he cared about my work. This pushed me to keep working hard. His contribution is so large that I almost feel as if he were a co-author of this thesis. I would also like to thank my "step" supervisor at MIT, Professor Jake Kerwin, for his insightful and friendly advices on both good (rarely) and bad (mostly) results. He made comments always in a humorous way. I sometimes didn't realize the funny point until Todd Taylor explained it for me. Professor Dimitris Bertsimas of the Sloan School of Management accepted to become a member of my thesis committee as an expert in optimization. He attended all the committee meetings and gave many useful comments from an optimization point of view, which I would have missed without him. Dr. Ki-Han Kim of DTMB traveled all the way from Washington D.C. sometimes via Minneapolis to MIT and provided many practical suggestions, which I believe made this thesis more valuable. I was really lucky to get to know smart Propnut members: Dr. Dave Keenan, Dr. Charlie Mazel, Dr. Ching-Yeh Hsin, Dr. Neal Fine, Dr. Mike Hughes, Dr. Tatsuro Kudo, Ms. Beth Lurie, Mr. Todd Taylor, Mr. Scott Black, Mr. Bill Milewski, Mr. Cedric Savineau, Mr. Wes Brewer, Dr. Bill Ramsey, Mr. Rich Kimball, Mr. Gerard Mchugh, Ms. Dianne Egnor, and Ms. Barbara Smith. Weekly group meetings were very helpful to get useful hints in my own research and to know other researches that were going on. Bill Milewski took time to review my thesis draft and gave me good suggestions on it. Dr. Takashi Maekawa has been a good friend and I enjoyed talking with him over lunch. Mr. Tatsuo Mori and Mr. Hideki Shimizu deserve credit for their friendship with me. I would like to thank my former supervisors at the University of Tokyo, Professors Koichiro Yoshida, Hiroharu Kato, and Hideyuki Suzuki for their encouragements. Professor Toshikazu Murakami of Tokai University is the person who made me consider studying at MIT, without whom I wouldn't even have started hydrodynamics research. Special thanks go to my host family, Dr. and Mrs. Seigo Matsuda, who made my stay in Boston always much easier and more enjoyable. Finally I would like to thank my wife, Naomi, for everything. I owe too much to her. Much of the computation was performed remotely on "cavity", a DEC Alpha 600(5/266) computer of the Ocean Engineering Group in the Department of Civil Engineering at the University of Texas at Austin. This research was supported by an international consortium of the following companies and research centers: Daewoo Heavy Industries Ltd., David Taylor Model Basin, El Pardo Model Basin, Hamburg Ship Model Basin, Hyundai Heavy Industries Co., Ltd., Ishikawajima-Harima Heavy Industries Co., Ltd., KaMeWa AB, Mercury Marine, Michigan Wheel Corporation, Outboard Marine Corporation, Rolla SP Propellers SA, Sulzer-Escher Wyss GmbH, Ulstein Propeller AS, Volvo-Penta of the Americas, and Widrtsili Propulsion Financial support for my stay at MIT was provided by the Technical Research & Development Institute, Japan Defense Agency.

Design of high performance supercavitating propellers based on a vortex lattice method

Citations

Analysis of supercavitating and surface-piercing propeller flows via BEM

Numerical Modeling of Supercavitating and Surface-Piercing Propeller Flows

Design of cavitating propeller blades in non-uniform flow by numerical optimization

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