Numerical Simulation Of Hydrodynamic Cavitation Based On FLUENT

Cavitation is a weeny gas bubbles (or called gas nucleus) suddenly growing phenomenon, which arosed by local low pressure (lower than saturated steam pressure at the same temperature) in the liquid. Cavitation is classified into four types based on the mode of its generation: acoustic cavitation, optic cavitation, particle cavitation and hydrodynamic cavitation. Hydrodynamic cavitation occurs in many cases, such as in piping with diameter suddenly changed, and in waterpower mechanism. Using extreme condition (high temperature, high pressure, strong bow wave and high speed jetflow) arosed by hydrodynamic cavitation could strengthen many technologic processes. So, hydrodynamic cavitation is widely applied in many fields.Along with the development of computational fluid dynamics (CFD), numerical simulation is applied more and more widely due to its high efficiency, low cost and well adaptability. In this thesis, the CFD software FLUENT is used to simulate the flow fields of cavitation in the venturi. The influences of the operation parameters and physical characters and structures on cavitation effect are investigated, and some conclusions are educed.1. In FLUENT, the standard k-ε model and the cavitation bubble dynamics model could be used to simulate the hydrodynamic cavitation in the venturi.2. When outlet pressure is constant, increasing inlet pressure could enhance cavitation effect.3. The saturated steam pressure of the liquid increases when temperature increases, which is propitious to engendering cavitation. And at the same time, the gas dissolved in the liquid decreases, which is not propitious to engendering cavitation. At about 40℃, the vapor fraction of the cavitation core area is the least, and cavitation effect is the weakest.4. The viscosity of the liquid restrains cavitation effect. The more viscous the liquid is, and the weaker cavitation effect is.5. The influence of the surface tension on cavitation is not evident.6. When the gas dissolved in the liquid is very little, cavitation effect enhances along with the increasing of the gas. And when the gas increases to some degree, cavitation effect weakens along with the increasing of the gas.7. When the wall roughness of the venturi increases, the vapor fraction of the cavitation core area also increases.8. The gular diameter and inlet angle and outlet angle of the Venturis have an important influence upon hydrodynamic cavitation. And according to the results of the simulation, several strategies for the optimization of venturi are proposed.