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Master's Dissertation
DOI
10.11606/D.3.2016.tde-11072016-093245
Document
Author
Full name
Gustavo Bochio
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2015
Supervisor
Committee
Assi, Gustavo Roque da Silva (President)
Conti, Mardel Bongiovanni de
Sbragio, Ricardo
Title in Portuguese
Estudo numérico do efeito de blocagem hidrodinâmica em um túnel de cavitação sobre o escoamento ao redor de um submarino.
Keywords in Portuguese
Escoamento
Hidrodinâmica
Submarinos (Projeto)
Túneis (Ensaios)
Abstract in Portuguese
O projeto de submarinos é um tema que vem se desenvolvendo há muitos anos. No Brasil, vivemos um momento de pleno avanço na área, sendo encabeçado pela Marinha do Brasil com o desenvolvimento do primeiro submarino de propulsão nuclear brasileiro. No decorrer desse projeto, diversos estudos devem ser desenvolvidos, dentre eles, ensaios com modelos em escala, que serão realizados em um túnel de cavitação. Durante estes experimentos, espera-se que surjam diversas fontes de incerteza, que podem comprometer os resultados obtidos, destacando-se o efeito de blocagem hidrodinâmica. Nesse contexto, esta dissertação apresenta uma investigação do fenômeno de blocagem no modelo de submarino DARPA SUBOFF na seção de testes de um túnel de cavitação. Para isso, simulações tridimensionais de média de Reynolds (RANS) foram realizadas para o modelo de submarino posicionado no túnel (sob blocagem) e sob condição de águas profundas (referência), para diferentes ângulos de ataque e número de Reynolds (Re) constante. Coeficientes de força e momento hidrodinâmicos foram obtidos e os métodos de correção de blocagem clássico e WICS foram empregados para obter fatores que pudessem corrigir esses valores. A eficiência de cada método foi avaliada comparando os valores corrigidos com os de referência. Os resultados mostraram que ambos métodos de correção são eficientes na recuperação de coeficientes de força e momento hidrodinâmicos para razões de blocagem inferiores a 10%, mas ressalvas são feitas quanto à utilização de cada um desses métodos, sendo o método clássico indicado para o estudo de geometrias simples e o método WICS para modelos mais complexos. Paralelamente, a topologia do escoamento ao redor do submarino foi estudada através do método dos pontos críticos, para avaliar se a blocagem hidrodinâmica pode causar alterações nas estruturas presentes no escoamento. A análise topológica permitiu avaliar a evolução nas estruturas do escoamento para os ângulos de ataque e Re simulados. Foram capturadas as linhas de separação no corpo e avaliada sua relação com a tensão de cisalhamento ao longo do casco. A blocagem hidrodinâmica não causou alterações drásticas na topologia do escoamento.
Title in English
Numerical study of the effect of hydrodynamic blockage in a cavitation tunnel in the flow around a submarine.
Keywords in English
Flow
Hydrodynamic
Submarines (Project)
Tunels (Tests)
Abstract in English
The Project of submarines has been in development for years. In Brazil, we are facing a moment of full progress in this area, leaded by the Brazilian Navy with the development of the first submarine with nuclear propulsion in the country. During this project, many studies will be developed, among them, experiments with scaled models, that will be performed in a cavitation tunnel. Throughout these experiments, many sources of uncertainty are expected to arise that may compromise the results obtained, one effect that stands out is the hydrodinamic blockage. In this context, this master's thesis presents an investigation of the blockage phenomenon in the submarine model DARPA SUBOFF placed in the test section of a cavitation tunnel. To accomplish this, tridimensional simulations of Reynolds-Averaged Navier Stokes equations (RANS) were performed to the submarine model placed in the tunnel (under blockage) and in deep water condition (reference), to a variety of angles of attack and a constant Reynolds Number (Re). Cofficients of hydrodynamic forces and moment were measured and the classic and WICS correction methods were used to obtain factors that could correct these values. The efficiency of these methods were evaluated comparing the corrected values with the reference ones.The results showed that both correction methods are efficients in the recovery of hydrodynamic forces and moment to blockage ratios below 10%, but reservations are made about the use of each method. The classic method is suggested when simple geometries are tested and the WICS method when more complex models are used. At the same time, the flow topology around the submarine was studied, using the critical point theory, to evaluate if the hydrodynamic blockage can cause changes in the structures in the flow. The topology analysis permited to assess the evolution of structures in the flow to the conditions of angle of attack and Re simulated. Separation lines were captured in the body and their relationship with the shear stress in the hull was evaluated. The hydrodynamic blockage did not cause drastic changes in the flow topology.
 
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GustavoBochio2015.pdf (25.60 Mbytes)
Publishing Date
2016-07-11
 
WARNING: The material described below relates to works resulting from this thesis or dissertation. The contents of these works are the author's responsibility.
  • BOCHIO, G., and ASSI, G. R. S. Numerical investigation of the effect of blockage on the hydrodynamic coefficients of a prolate spheroid. In ASME 2014 Fluids Engineering Summer Meeting (FEDSM2014), Chicago, 2014. ASME 2014 Fluids Engineering Summer Meeting (FEDSM2014)., 2014.
All rights of the thesis/dissertation are from the authors
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