Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Science, 1981. / Microfiche copy available in Archives and Science. Film reel in Science Library. / Bibliography: leaves 79-80. / by Peter John Vrolijk. / M.S.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Foi implementado, na linguagem Visual Basic 6, um programa computacional para a anÃlise do Golpe de ArÃete em adutoras, utilizando-se do MÃtodo das CaracterÃsticas e das equaÃÃes caracterÃsticas de equipamentos normalmente encontrados nos sistemas hidrÃulicos. Procurou-se desenvolver um aplicativo que possibilite ao usuÃrio visualizar o comportamento das ondas de sobrepressÃo e subpressÃo decorrentes do fenÃmeno transitÃrio, alÃm de verificar a influÃncia da chaminà de equilÃbrio e do tanque de alimentaÃÃo unidirecional (TAU) como dispositivos de alÃvio do golpe de arÃete. Aplicou-se o modelo computacional na anÃlise dos transientes hidrÃulicos gerados pelo desligamento do conjunto moto-bomba, e na avaliaÃÃo da eficiÃncia da chaminà de equilÃbrio e do tanque de alimentaÃÃo unidirecional como mecanismos de atenuaÃÃo dos picos de pressÃo. A validaÃÃo do modelo se deu atravÃs da comparaÃÃo dos resultados das simulaÃÃes com os dados obtidos nos testes realizados utilizando-se o CTran, software desenvolvido pela FundaÃÃo Centro TecnolÃgico de HidrÃulica da Escola PolitÃcnica da Universidade de SÃo Paulo. De acordo com a anÃlise estatÃstica, o programa desenvolvido apresentou resultados bastante satisfatÃrios na anÃlise do golpe de arÃete, possuindo uma interface de fÃcil utilizaÃÃo e visualizaÃÃo dos resultados, fato de fundamental importÃncia para que projetistas e estudantes compreendam o comportamento do fenÃmeno. / The main goal of this research is the development of the computer code designed to model the water hammer problem which occurs in water pipes. It was used the method of characteristics to numerically solve the differential equations which control the problem. The software developed allows the user to visualize the behavior oh the over and under pressure waves resulting from the occurrence of the transient problem. Other features of the developed software includes the possibility of analyzing the introduction of mechanisms to decrease the effects of the water hammer problem such as orifice tanks, one-way tanks, closed tanks and relief valves. The developed model was applied and validated to water conducts which was previously been analyzed by the software CTran, developed by the âEscola PolitÃcnica de Universidade de SÃo Pauloâ. The results were very satisfactory

Buffer tanks are widely used within the process industry to prevent flow variations from being directly propagated throughout a plant. The capacity of the tank is used to smoothly transfer inlet flow upsets to the outlet. Ideally, the tank thus works as a low pass filter where the available tank capacity limits the achievable flow smoothing. For infrequently occurring upsets, where the system has time to reach steady state between flow changes, the averaging level control problem has been extensively studied. After an inlet flow change, flow filtering has traditionally been obtained by letting the tank level deviate from its nominal value while slowly adapting the outlet to cancel out the flow imbalance and eventually bringing back the level to its set-point. The system is then again in steady state and ready to surge the next upset. By ensuring that the single largest upset can be handled without violating the level constraints, satisfactory flow smoothing is obtained. In this thesis, the smoothing of frequently changing inlet flows is addressed. In this case, standard level controllers struggle to obtain acceptable flow smoothing since the system rarely is in steady state and flow upsets can thus not be treated as separate events. To obtain a control law that achieves optimal filtering while directly accounting for future upsets, the averaging level control problem was approached using robust model predictive control (MPC). The robust MPC differs in the way it obtains flow smoothing by not returning the tank level to a fixed set-point. Instead, it lets the steady state tank level depend on the current value of the inlet flow. This insight was then used to propose a linear control structure, designed to filter frequent upsets optimally. Analyses and simulation results indicate that the proposed linear and robust MPC controller obtain flow smoothing comparable to the standard optimal averaging level controllers for infrequent upsets while handling frequent upsets considerably better.