Numerical Study of Cavitation within Orifice Flow
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Cavitation generally occurs when the pressure at certain location drops to the vapor pressure and the liquid water evaporates as a consequence. For the past several decades, numerous experimental researches have been conducted to investigate this phenomenon due to its degradation effects on hydraulic device structures, such as erosion, noise and vibration. A plate orifice is an important restriction device that is widely used in many industries. It serves functions as restricting flow and measuring flow rate within a pipe. The plate orifice is also subject to intense cavitation at high pressure difference, therefore, the simulation research of the cavitation phenomenon within an orifice flow becomes quite essential for understanding the causes of cavitation and searching for possible preventing methods. In this paper, all researches are simulation-oriented by using ANSYS FLUENT due to its high resolution comparing to experiments. Standard orifice plates based on ASME PTC 19.5-2004 are chosen and modeled in the study with the diameter ratio from 0.2 to 0.75. Steady state studies are conducted for each diameter ratio at the cavitation number roughly from 0.2 to 2.5 to investigate the dependency of discharge coefficient on the cavitation number. Meanwhile, a study of the flow regime transition due to cavitation is also carried out based on the steady state results. Moreover, a transient study is done to clarify the relationship between cavitation at the orifice and cavitation at the downstream pipe wall. Several conclusions can be made from this numerical study. The discharge coefficient of the orifice plate is independent of cavitation number; As cavitation number decreases, cavitation tends to be more intense and the flow regime transit to super cavitation eventually; In addition to cavitation occurring at the orifice edge, it also initiates at downstream pipe wall.
Yang, Pengze (2015). Numerical Study of Cavitation within Orifice Flow. Master's thesis, Texas A & M University. Available electronically from