Research On The Basic Theory Of Water Hammer And Water Hammer Wave

Water hammer always led to the damage of the pump, valves, and the guide blade of the hydroturbine, the burst of the pressure pipeline, a great deal of water leakage and so on, which has been much attention all the time as one of the important effect factors on the security of pressure pipeline system. Currently the classical water hammer theory used widely has been a history of more than one hundred years, and the calculation methods were emerging in an endless stream afterwards. However, the basic differential equations used in water hammer calculation have been some problems to solve, and the water hammer theory need to be further verified and consummated.In this thsis, the traditional water hammer theories and mathematic models were introduced firstly, some problems and the possible reasons were pointed in the theories.Then, on the basic of correcting the wrong concepts, the mathematical calculating models of the closed equations used in water hammer were improved, completed and calculated. Comparing with the calculation of the traditional water hammer equations, the rationality and reliability of the closed equations which have been completed were checked. Meanwhile, the varying pattern of the pipeline section area, liquid density, fluid velocity and the response to the result of changes in water hammer pressure when water hammer happened were calculated and analysed.In the theoretical research, on the attributes of water hammer, using the research object which can reflect the propagation characteristic of water hammer wave exactly, the theory of water hammer was reduced and studied scrupulously through the application for the principle of mass conservation and the theorem of momentum.Finally, based on the fact that water hammer was simulated and calculated accurately, the variation of water-hammer wave speed was caught and researched seriously.The chief opinions are:1.Some conceptual issues existed in the traditional equation of water hammer calculation when it was established,which especially can’t reflect the decay law of water hammer exactly. The closed equations which has been completed and used in the water hammer calculation in this paper can not only simulate the peak pressure fluctuations in the inner system accurately when water hammer happened, but also can reflect the decaying process of water hammer waves precisely.2.The pipeline section area and liquid density changed inconstantly when water hammer occured. But relative to the change of water hammer pressure,the variation of the pipeline section area and liquid density was very tiny.3.The study of the theory in this paper showed that the correct formulas of water hammer waves may not be deduced by the general approach now, which need to be further explored through other methods.4.Through catching and computational simulation to the change law of the water-hammer wave speed, the dissertation showed that water-hammer wave speed was not a constant along pipeline, which changed as the pressure, density, pipeline section changed, wherever the water hammer wave arrived.