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Authors
Abstract(s)
Esta dissertação será desenvolvida no âmbito de várias unidades curriculares
leccionadas no mestrado integrado em Engenharia Naval ramo de Armas e Electrónica, e tem como objectivo contribuir para a produção de conhecimento científico
da Marinha. Sendo Portugal um país maioritariamente marítimo, tudo o que lhe
diz respeito tem interesse para o país e por isso torna-se importante um cada vez
maior e melhor conhecimento na área da acústica submarina, que serve de suporte
a muito do trabalho de investigação e caracterização do meio submarino.
O problema que ser pretende resolver é a modelação de raios acústicos submarinos segundo um modelo de geometria diferencial capaz de ter em conta as
heterogeneidades e movimentos do meio de propagação. Para se conseguir cumprir este objectivo serão estudadas as equações que definem estes fenómenos e será
criado um modelo que se irá testar em fontes hidrotermais. Mas é de relevância
referir que o mesmo pode ser aplicado a outros exemplos como as zonas costeiras,
com a condicionante de que o efeito só será visível a maiores distâncias (kms) e os
resultados não seriam tão fidedignos já que o modelo utilizado não tem em conta a
dissipação do som. Como é sabido, terá de ser considerada uma gama de frequências
suficientemente altas para que seja válida a aproximação geométrica.
Através de três diferentes expressões que relacionam a velocidade do som
com a temperatura, que em traços largos são as disponiveis presentemente e utilizadas em outros trabalhos, são analisados os comportamentos dos diferentes parâmetros e o impacto que têm nas trajectórias dos raios acústicos junto das fontes
hidrotermais.
Após o cálculo analítico, resolvem-se as equações obtidas num programa
MATLAB onde, através do código aqui desenvolvido, se pode ter acesso aos mais variados gráficos do trajecto que os raios descrevem, sendo que o "emissor"considerado
nestes gráficos não é nada mais do que o raio central de cada uma das ondas sonoras.
This dissertation will be developed within the scope of several curricular units taught in the integrated master’s degree in Naval Engineering in the speciality of Weapons and Electronics, and aims to contribute to the production of scientific knowledge in the Portuguese Navy. As Portugal is mainly a martime country, everything that concerns it is of interest to the country and that is why it is important to have greater and better knowledge in the area of underwater acoustics, which we know, supports several of the research and caracterization work of the underwater environment. The problem to be solved is the modeling of underwater acoustic rays according to a model of dierential geometry capable of taking into account the heterogeneities and movements of the propagation medium. In order to achieve this objective, the equations that define these phenomena will be studied and a model will be created that will be tested in hydrothermal sources. But it is important to mention that the same can be applied to other examples such propagation near coastal zones with the condition that the eect would be visible only at greater distances (kms) and the results would not be as reliable as the model used does not take into account the dissipation of sound in the water. As is know, a suciently high frequency range will be assumed for the geometric approximation to be valid. Through three dierent expressions that relate the speed of sound to temperature, which in broad lines respond are some of the ones presently available and usedin other works, the behavior of the dierent parameters and the impact they have on the trajectories of acoustic rays near hydrothermal vents are analysed. After the analytical calculation, the equations obtained in a MATLAB program are solved, where, through the code herein developed, allow access to the most varied graphics of the path that the rays describe. The "emitter"considered in these graphics is nothing more than the central ray of each sound wave.
This dissertation will be developed within the scope of several curricular units taught in the integrated master’s degree in Naval Engineering in the speciality of Weapons and Electronics, and aims to contribute to the production of scientific knowledge in the Portuguese Navy. As Portugal is mainly a martime country, everything that concerns it is of interest to the country and that is why it is important to have greater and better knowledge in the area of underwater acoustics, which we know, supports several of the research and caracterization work of the underwater environment. The problem to be solved is the modeling of underwater acoustic rays according to a model of dierential geometry capable of taking into account the heterogeneities and movements of the propagation medium. In order to achieve this objective, the equations that define these phenomena will be studied and a model will be created that will be tested in hydrothermal sources. But it is important to mention that the same can be applied to other examples such propagation near coastal zones with the condition that the eect would be visible only at greater distances (kms) and the results would not be as reliable as the model used does not take into account the dissipation of sound in the water. As is know, a suciently high frequency range will be assumed for the geometric approximation to be valid. Through three dierent expressions that relate the speed of sound to temperature, which in broad lines respond are some of the ones presently available and usedin other works, the behavior of the dierent parameters and the impact they have on the trajectories of acoustic rays near hydrothermal vents are analysed. After the analytical calculation, the equations obtained in a MATLAB program are solved, where, through the code herein developed, allow access to the most varied graphics of the path that the rays describe. The "emitter"considered in these graphics is nothing more than the central ray of each sound wave.
Description
Keywords
Acústica Submarina Aproximação Geométrica Raios Acústicos Fontes Hidrotermais Geometria diferencial