Estudo da atenuação de sinal de vazamento de água em tubos de PVC com longarinas metálicas longitudinais
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Data
2020-07-16
Autores
Lima, Luis Paulo Morais
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Universidade Estadual Paulista (Unesp)
Resumo
A água potável é um recurso indispensável e, por isso, é importante que se evite desperdícios por quaisquer causas, dentre elas, vazamento em redes de distribuição. Porém, a detecção de vazamento em tubulações subterrâneas é dificultada devido ao material plástico do qual geralmente são feitos os tubos. Isso porque este material atenua as ondas mecânicas geradas pelos vazamentos e que servem, justamente, de sinal para que se possa detectá-los e localizá-los. Este trabalho propõe um novo tipo de tubo para reduzir o efeito natural, porém indesejável, da atenuação. Trata-se do mesmo tubo de plástico acrescido de longarinas metálicas longitudinais que tem a função não de enrijecê-lo, mas de serem meios menos atenuantes para as ondas mecânicas. Esta proposta foi modelada matematicamente acoplando-se uma casca cilíndrica fina a uma viga que transmite ondas de flexão e compressão. As equações de movimento para uma longarina acoplada ao tubo foram obtidas e, a partir delas, foi determinada a relação de dispersão do sistema, a qual foi usada para avaliar a atenuação do novo tubo. Simulações numéricas usando o Método dos Elementos Finitos foram feitas para validar os resultados teóricos sem preencher o tubo com água. Os resultados do modelo mostraram uma melhora bastante expressiva para ondas longitudinais na casca, com redução de 96% da atenuação. Esta predição, entretanto, está superestimada devido a uma limitação do modelo, que não admite transmissão de energia entre a casca e as longarinas, a qual resultaria em mais atenuação. Por fim, algumas sugestões de trabalhos futuros são feitas para que o modelo seja corrigido e se torne mais realista.
Water is an indispensable resource, and as such it is important that waste of any source is avoided, among them, by leakage in distribution networks. However, leakage detection in underground pipes is difficult due to the plastic material of which pipe is usually made. That is because plastic materials attenuate the mechanical waves generated by the leakage which are used as signal to detect and locate their source. This work proposes a new type of pipe to reduce this however natural, still undesirable effect. The pipe is the same plastic-made one with added longitudinal metallic stringers which are not supposed to stiffen it, but to be a less attenuating medium for the mechanical waves. This proposal was mathematically modeled coupling a thin cylindrical shell and a beam capable of conveying flexural and compressional waves. The equations of motion for a stringer coupled to the pipe were obtained and, from them the system's dispersion relationship was derived, which was used to evaluated the attenuation in the new pipe. Numerical simulations using the Finite Element Method were carried out to validate theoretical results without filling the pipe with water. The theoretical results show an expressive improvement for longitudinal waves in the shell, with a reduction of 96% of the attenuation. This prediction, however, is overestimated because the models does not account for the transmission of energy between the shell and the stringers, which would result in more attenuation. At last, some suggestions for future works are made to correct and make the model more realistic.
Water is an indispensable resource, and as such it is important that waste of any source is avoided, among them, by leakage in distribution networks. However, leakage detection in underground pipes is difficult due to the plastic material of which pipe is usually made. That is because plastic materials attenuate the mechanical waves generated by the leakage which are used as signal to detect and locate their source. This work proposes a new type of pipe to reduce this however natural, still undesirable effect. The pipe is the same plastic-made one with added longitudinal metallic stringers which are not supposed to stiffen it, but to be a less attenuating medium for the mechanical waves. This proposal was mathematically modeled coupling a thin cylindrical shell and a beam capable of conveying flexural and compressional waves. The equations of motion for a stringer coupled to the pipe were obtained and, from them the system's dispersion relationship was derived, which was used to evaluated the attenuation in the new pipe. Numerical simulations using the Finite Element Method were carried out to validate theoretical results without filling the pipe with water. The theoretical results show an expressive improvement for longitudinal waves in the shell, with a reduction of 96% of the attenuation. This prediction, however, is overestimated because the models does not account for the transmission of energy between the shell and the stringers, which would result in more attenuation. At last, some suggestions for future works are made to correct and make the model more realistic.
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Palavras-chave
Propagação de ondas, Casca cilíndrica enrijecida, Detecção de vazamentos, Wave propagation, Stiffened cylindrical shell, Leakage detection