| Summary: | 碩士 === 國立成功大學 === 航空太空工程學系 === 83 === PISO algorithm is adopted to calculate the flow field in a
suddenly contracted injector orifice under a certain range of
Reynolds numbers. In the present study PISO algorithm demons-
trates to possess good numerical stability in using large time
steps for steady flows. It also has well-accepted transient
accuracy to be an alternative choice for unsteady flows. As far
as the steady flow of the injector orifice is concerned, a re-
circulation zone is predicted to occur in the vicinity of the
entrance of the orifice to form vena contracta at certain Rey-
nolds number. The length of the recirculation zone increases
with the increasing Reynolds number. The local pressure,
however, descends as the Reynolds number increases. Since
cavitation occurs as the local pressure drops down to the vapor
pressure, the minimum pressure in the flow field is predicted
under various Reynolds numbers. In a comparision between this
minimum pressure and the vapor pressure at the given operating
condition, the flow condition at which and location where
cavitation incepts are identified.
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