To measure vibration characteristics induced by cavitating flow, a model pump made of stainless steel is designed; besides a transparent model pump of Plexiglass is also made to visualize the cavitating flow versus cavitation number decreasing.
The corresponding cavitation number is defined as in
In study of cavitating flow, a dimensionless parameter [sigma] is often used to characterize the extent of cavitation, namely, cavitation number, defined as [sigma] = 2 ([p.sub.[infinity]] - [p.sub.c)]/[rho][V.sup.2], where [rho] is the density of water, [p.sub.[infinity]] is the ambient pressure at infinity, [p.sub.c] is the cavity pressure, and V refers to the velocity of vehicle [4].
According to fluid dynamics exerted on different parts of supercavitating vehicle, the dynamic model [7] can be established with cavitation number [sigma] and feedback control gain of fin deflection angle k as variable parameters:
The cavitating flow regimes related to the
cavitation number, [sigma] = 0,59, and [sigma] = 0,64 defined the value of the saturation pressure [P.sub.c].
where: K =
cavitation number, [P.sub.w] = pressure at the cylinder wall, [P.sub.v] = vapor pressure of the coolant, ??
In view of the desired and anticipated range of
cavitation numbers and with the selected range of test section flow velocities, the range of test section static pressure was chosen to be 0.5 to 60 psia (3.5 to 415 kPa, 0.03 to 4 atmospheres), specified to apply at a point at the top of the downstream end of the test section.