As the U.S. Navy develops new technologies which enhance automation and reduce crew size onboard naval vessels, unmanned vehicles will become increasingly valuable in conducting maritime operations. Effective launch and recovery systems (LARS) are necessary for unmanned vehicles to efficiently conduct operations at sea. The Towed Body system is a LARS with a wide range of applications for unmanned vehicle operations. The Towed Body can be evaluated as a small vessel with horizontal and vertical control surfaces. Since it is being towed, the directional stability of the Towed Body requires unique consideration due to the presence of the towing force. This thesis examines the effect of varying the longitudinal location of the vertical control surfaces, as well as the effective aspect ratio, size, and number of vertical control surfaces. The results identify critical stability values for the various fin configurations.

Denna uppsats handlar om eskortbogsering och hur lotsars inställning är till att använda sig av detta. Den metod som använts är kvalitativ och ansatsen hypotetiskt deduktiv. Utifrån intervjuerna med lotsar som genomfördes i Göteborgs hamn märktes generellt att lotsarna är positivt inställda till att använda sig av eskortbogsering även om deras åsikter i vissa fall går isär om vilka fartyg som reglerna skall omfatta. I uppsatsen görs även jämförelser med en tidigare amerikansk studie gjord på området Puget Sound, som sedan används som underlag för Göteborgs hamn och Västkusten.  Slutsatsen är att lotsarnas inställning till användning av eskortbogseringen kommer säkert att vara densamma med tanke på att sjöfarten som bransch växer och transporterna världen över ökar. Det kan antas att kraven på säkerhet kommer att höjas. I detta fall kan det betyda att fler hamnar kan komma att ta efter Göteborg när det gäller krav och regler angående eskortbogsering. / This paper deals with escort towing and the pilots’ attitudes towards the usage of this. The method used is qualitative and the approach is hypothetico-deductive.  Results from the interviews conducted with pilots in Gothenburg harbor gave an impression that, in general, the pilots favored the use of escort towing although their opinions sometimes differed on what type of ships should be included and excluded by escort regulations. To further the study, a comparison has been made to an earlier American report on the Puget Sound area by using it as a basis for the Port of Gothenburg and the West Coast. The conclusion is that the pilots' attitudes towards escort towing will surely be the same given that the shipping industry is growing as well as transportation worldwide is increasing. With this in mind, it can be assumed that the requirements of safety will increase. In this case, it is believed that more ports may take after Gothenburg in terms of requirements and rules regarding escort towing.

Thesis (M.S.)--Rochester Institute of Technology, 2007. / Typescript. Includes bibliographical references (leaves 113-117).

Thesis (M.S. in Systems Engineering)--Naval Postgraduate School, June 2008. / Thesis Advisor(s): Whitcomb, Clifford. "June 2008." Description based on title screen as viewed on September 2, 2008. Includes bibliographical references (p. 63-65). Also available in print.

No description available.

Deltastream is an on-going project carried by Tidal Energy Limited since almost twenty years. It is a tidal energy converter with a triangular shape and one turbine on each tower. It has gone through many evolutions of design but a first prototype will be installed in the end of 2014 at Ramsey Sound. The deployment and recovery operations will be carried out with a single lift point through a heavy lift frame. Two issues have to be tackled during the operation: the rate of flooding of the ballasts and the tension on the lift crane cable. The most favourable sea state must be found in order to minimise the crane cable tension as well as the best inlets and outlets configuration for the ballasts system. In order to tackle those issues, preliminary analytical work was conducted on the demonstrator to assess the stability during the flooding process. A scaled model was designed and built in order to be tested in a wave-towing tank. The results from the tests highlight that the deployment and the recovery operations are safe for both the barge and Deltastream for the range of wave conditions tested in the tank. However, the sea state has an important impact on the proceeding of the operations, especially the period of the waves.

Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, March 2005. / Thesis Advisor(s): Fotis Papoulias. Includes bibliographical references (p. 63-64). Also available online.

Slender structures in fluid flow exhibit a variety of rich behaviors. Here we study the equilibrium shapes of perfectly flexible strings that are moving with a uniform velocity and axial flow in viscous fluid. The string is acted upon by local, anisotropic, linear drag forces and a uniform body force. Generically, the configurations of the string are planar, and we provide analytical expressions for the equilibrium shapes of the string as a first order five parameter dynamical system for the tangential angle of the body ($theta$). Phase portraits in the angle-curvature ($theta,partial_s theta$) plane are generated, that can be shown to be $pi$ periodic after appropriate scaling and reflection operations. The rich parameter space allows for different kinds of phase portraits that give rise to a variety of curve geometries. Some of these solutions are unstable due to the presence of compressive stresses. Special cases of the problem include sedimenting filaments, dynamic catenaries, and towed strings. We also discuss equilibrium configurations of towed cables and other relevant problems with fixed boundary conditions. Special cases of the boundary value problem involve towing of neutrally buoyant cables and strings with pure axial flow between two fixed points. / Master of Science

Dissertação(mestrado) - Universidade Federal do Rio Grande, Programa de Pós-Graduação em Engenharia Oceânica, Escola de Engenharia, 2008. / Submitted by Lilian M. Silva (lilianmadeirasilva@hotmail.com) on 2013-04-19T22:08:47Z No. of bitstreams: 1 Desenvolvimento De Uma Instalação Experimental Para Estudo De Fenômenos De Interação Fluido-estrutura.pdf: 1830430 bytes, checksum: fbf20ca5696e6496fdf803ca403c6632 (MD5) / Approved for entry into archive by Bruna Vieira(bruninha_vieira@ibest.com.br) on 2013-06-03T19:29:51Z (GMT) No. of bitstreams: 1 Desenvolvimento De Uma Instalação Experimental Para Estudo De Fenômenos De Interação Fluido-estrutura.pdf: 1830430 bytes, checksum: fbf20ca5696e6496fdf803ca403c6632 (MD5) / Made available in DSpace on 2013-06-03T19:29:51Z (GMT). No. of bitstreams: 1 Desenvolvimento De Uma Instalação Experimental Para Estudo De Fenômenos De Interação Fluido-estrutura.pdf: 1830430 bytes, checksum: fbf20ca5696e6496fdf803ca403c6632 (MD5) Previous issue date: 2008 / O estudo experimental de problemas de interação fluido-estrutura é de fundamental importância para o entendimento dos processos dinâmicos envolvidos. Esses processos podem ser bastante complexos em função da alta não-linearidade do problema, especialmente para os casos em que o acoplamento entre a dinâmica do fluido e a dinâmica da estrutura é forte, ou para casos em que ocorram instabilidades dinâmica tanto no fluido quanto na estrutura. O estudo experimental de fenômenosde interação fluido-estrutura necessita de instalações de laboratório capazes de impor movimento relativo entre o fluido e a estrutura. Neste contexto, nesta dissertação apresentam-se o projeto, a construção e a avaliação de um canal de reboque otimizado para o estudo da interação fluido-estrutura em corpos rombudos cilíndricos de alta razão de aspecto. A instalação consiste de um canal de 16 m de comprimento com seção transversal 0,71m de largura por 0,79 m de altura e de uma plataforma de reboque para movimento da estrutura sobre o fluido. Além do movimento retilíneo, a plataforma de reboque é capaz de impor, simultaneamente, movimentos oscilatórios em até dois grupos de estruturas de forma independente. Esta capacidade permite o estudo da influência da amplitude, da freqüência e da fase do movimento oscilatório na interação entre o fluido e as estruturas. A dissertação contém uma discussão sobre a formulação geral dos problemas de interação fluido-estrutura e os principais parâmetros adimensionais relevantes. São tratados os problemas específicos da instalação experimental tais como especificação dos parâmetros hidrodinâmicos, projeto das estruturas de suporte do canal e da plataforma de reboque, o projeto mecânico da plataforma de reboque e uma breve descrição do sistema de controle dos movimentos da plataforma, bem como apresentam-se a descrição dos ensaios de avaliação de desempenho do sistema e a discussão dos resultados. Finalmente, a dissertação apresenta as conclusõesdos aspectos construtivos e capacidade da instalação em uma faixa do número de Reynolds, bem como as sugestões para trabalhos futuros. / The experimental study of fluid-structure interaction problems is of fundamental importance for the understanding of the dynamic phenomena involved. The dynamics of these phenomena can be very complex as a result of the high non-linearity of the problem, in particular for the cases with strong coupling between the dynamic of the fluid and the dynamic of the structure, or in cases in which instabilities in the fluid or in the structure are present. The experimental study of fluid-structure interaction requires laboratory facilities capable of impose relative motion between the fluid and the structure. In this context, that work presents the design, the construction and the evaluation of a towing canal optimized for the study of the interaction fluid-structure in cylindrical bluff bodies of high aspect ratio. The facility consists of 16 m long canal with cross section 0.71 m of width by 0.79 m of height and a towing platform for the motion of the structure in the fluid. In addition to the linear motion, the towing platform is capable of impose simultaneously independent transverse oscillatory motion in up to two structure groups. This capacityallows the study of the influence of the amplitude, of the frequency and of the phase of the oscillatory motion in the interaction between the fluid and the structure. This work presents a discussion on the general formulation of the fluid-structure interaction problems and on the main dimensionless parameters that are relevant to the problem. Next, it deals with the specification of the experimental facility such as hydrodynamic parameters, design of structures for supporting the canal itself and the towing platform, the mechanical design of the towing platform and a brief description of the system of control of the towing platformmotions. Next, it presents the description of the evaluation tests for the platform performance and the discussion of the results. Finally, the work presents the conclusions of the aspects of capacity building and installation on a range of Reynolds number, as well as suggestions for future work.

Calm water towing tank experiments consisting of resistance tests and static and dynamic planar motion mechanism (PMM) tests are performed for a surface combatant with primary focus on the effects of hurricane scale headwinds. The experiments are designed to gain a better understanding of the physics of ship response to wind and to provide a validation dataset for an unsteady Reynolds-averaged Navier Stokes (RANS)-based computational fluid dynamics (CFD) code used for computing both air and water flow around a ship. Hurricane scale wind speeds are chosen to maximize the measurable effect of wind on ship forces and motions for a more definitive analysis and comparison with CFD. The geometry is the 1/48.9 scale fully appended ONR Tumblehome model 5613, which has length L = 3.147 m and is equipped with a superstructure. Tests are performed in a 3.048 × 3.048 × 100 m towing tank with wind generated by a custom built wind carriage towed ahead of the ship model. Air-stream velocity measurements indicate a maximum relative wind speed magnitude of 9.38 m/s with 6 - 7% uniformity and RMS values of approximately 4.5%. The effects of three wind speeds on static and dynamic forces, moment, and motions are analyzed. Results show that wind contributes significantly to surge force (approximately 46% at Fr = 0.2). Resistance data shows agreement with CFD computations with errors averaging approximately 4%. The drag coefficient above water is approximately 0.3 and generally decreases with increasing ship speed. Sway force and yaw moment are largely affected when the ship experiences oblique orientation to the flow. Forces and moment exhibit quadratic scaling with wind speed. Roll is the most sensitive motion to wind and is counteracted by it up to 1.8° for PMM test conditions. In addition, harmonic amplitudes of forces and moment data from dynamic tests are used to determine hydrodynamic derivatives for all three wind conditions following a mathematical model. The effect of wind on hydrodynamic derivatives is significant with changes on the order of 10 - 100%.