. Cavitation inception and internal flows with cavitation. Cavitation. unsteady flows across cavitating pump cascades, we can see that a plausible form of the transfer function for a pump would be (with reference to the notation of Figure 38) (39) the circumflexes, again, refer to the unsteady fluctuations. In the limit of zero frequency, the steady pump performance curve must have the result that. '12 (40) tan 3 for infinitesimal excursions about the operating point. When the frequency is not zero we may expect that z and z become complex and that z and z will become important The steady stat
. Cavitation inception and internal flows with cavitation. Cavitation. unsteady flows across cavitating pump cascades, we can see that a plausible form of the transfer function for a pump would be (with reference to the notation of Figure 38) (39) the circumflexes, again, refer to the unsteady fluctuations. In the limit of zero frequency, the steady pump performance curve must have the result that. '12 (40) tan 3 for infinitesimal excursions about the operating point. When the frequency is not zero we may expect that z and z become complex and that z and z will become important The steady state pump test then provides limiting estimates of z and z . Much of the early work on hydraulic system dynamics involving cavitating pumps has been based upon the idea that the term z . is pre- cisely a "compliance" effect and that z was zero. The compliance was then determined by making a best fit to field data of observed system oscillations (see, , Rubin 1966). It was, of course, not necessary to assume z to be zero except for simplicity. Later, Brennen et al., (1976) showed from limiting quasi-steady arguments based on field data, that the term corresponding to z was, indeed, important, and that this term, as well as z , could be estimated from quasi-steady cavitating cascade theory. As it turned out, these estimates, even when the effects of blade thick- ness were included, underestimated the results of field observations by a fair amount, particularly so for the compliance term. It had been shown previously by Brennen (Brennen 1973) that the compliance effect due to 82. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Acosta, Allan J. , 1924-; David W. Taylor Naval Ship Research and Development Center. Bethesda, Md. : David W. Taylor Naval Ship Research and Development Center
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