Cavitation inception

The final estimation of the value of ay may appear tedious and several assumptions are made in its derivation, but experimental evidence suggests that it may be used with reasonable accuracy to assess the levels of potentially damaging cavitation erosion. In small valves with nominal bores up to 65 mm cavitation inception occurs in intermittent bursts when the value oy is approximately unity. The cavitation becomes continuous and audible as Oy is reduced to about 0.6, but the risk of damage does not become significant until the value falls below 0.4. As a design criterion the condition of light, steady noise has been described by Tullis as the critical level and is sug-... 

Ida M, Naoe T, Futakawa M (2007) Suppression of cavitation inception by gas bubble injection A numerical study focusing on bubble-bubble interaction. Phys Rev E 76 046309... 

During the last four decades, measurements of weak nuclei (i.e., gas nuclei) in liquids have become especially important in view of their influence on cavitation inception (e.g., ref. 57-59). Understandably, the gas nuclei concentration is closely coupled with the free gas content of the liquid (ref. 58, 60). (A distinction is made commonly in the engineering literature between free gas content and dissolved gas content. The free gas content is that portion of gas which has the normal physical properties of bulk gas. In practical situations, the free gas concentration within the liquid is usually several orders of magnitude lower than the dissolved gas concentration (ref. 58).) Many investigators have developed instruments to detect this free gas content (ref. 58,60) and the freestream gas nuclei concentration associated with it (e.g., ref. 58-60). 

F.G. Hammitt, D.M. Ericson, J.F. Lafferty and M.J. Robinson, Gas content, size, temperature, and velocity effects on cavitation inception in a venturi, Amer. Soc. Mech. Engin. paper 67-WA/FE-22,1968. 

A. Keller, The influence of the cavitation nucleus spectrum on cavitation inception, investigated with a scattered light counting method, J. Basic Engng. 94 (1972) 917-925. 

D.M. Oldenziel. New instruments in cavitation research, in W.B. Morgan and B.R. Parkin (Eds.), International Symposium on Cavitation Inception, American Society of Mechanical Engineers, New York, 1979, pp. 111-124. 

H. B. Marschall, K. A. Mprch, A. P. Keller, and M. Kjeldsen, Cavitation Inception by Almost Spherical Particles in Water, paper presented at the Fourth International Symposium on Cavitation, California Institute of Technology, Pasadena, CA, June 20-23, 2001. 

Strasberg, M., The Influence of Air-filled Nuclei on Cavitation Inception. David Taylor Model Basin, Navy Dept., Rept. No. 1078, 1957. 

Bapat, P.S. and A.B. Pandit, Insight into an Acoustic Cavitation Inception Role of Sound Energy and Water Medium, Ultrason. Sonochem., Forwarded for Publication, (2006). 

The effect of polymeric additives on collective phenomena, associated with the dynamics of bubbles, can be illustrated by the example of hydrodynamic cavitation, caused by abrupt decrease in local pressure (in flows around bodies, after stream contraction, in jets). It has been found that the use of polymers permits to decrease the cavitation noise, lower the cavitation erosion, and delay the cavitation inception. For example, adding a small amount of POE to a water jet issuing from the orifice caused the decrease of the critical cavitation number, K , by 35-40%. In experiments with rotating disk flic value of K, was decreased by 65% with addition of 500 ppm POE. Note, however, that these features are linked not only to the changes in individual bubble dynamics, but to the influence of macromolecules on the total flow regime as well. In particular, phenomena listed above are... 

Cavitation is the process of nucleation in a liquid and subsequent formation of gas/vapor phase when the pressure falls below a critical value. Researchers studying cavitation address topics ranging from the initial appearance of cavities in liquids (cavitation inception) to the development of large-scale cavities (supercavitation). 

Liquids undergoing tensions in stressing waves have been frequently investigated. A main goal of these investigations has been the determination of the threshold for cavitation inception and its dependence on various parameters. In this paper special attention will be paid to the details of the breaking dynamics of the liquid. Such dynamics are strongly influenced by cavitation nuclei which are almost always present in ordinary liquids. 

Cavitation studies in polymer solutions have centered on jet cavitation, cavitation inception on rotating disks, propellers, pumps and turbines. Jet cavitation studies,[20] show that the cavitation index can be reduced to a half of the previous value when small quantities of Polyox are present in the flow. The cavitation inception index is defined... 

In summary, this overview article discussed two types of micro-and nanoscopic surface bubbles. The first type—gas entrapped in controlled surface defects—serves as nucleation sites in cavitation experiments. For these bubbles cavitation inception and the result-... 

Fig. 2. Definition of the cavitation inception point (flow rate Qc) when pumping slurries. Hw and Hm are heads for water and slurry, respectively. The influence of cavitation, He, is defined as a 3% reduction of the head (Hm) developed in slurry service.

The fluid temperatures during the water and slurry experiments varied from 35 to 39°C, giving the vapor pressure, pvp. The atmospheric pressure, patm, was 101.9 kPa. The measured flow rates and gauge suction pressures, pgs are related to the cavitation inception criterion in Fig. 2. The NPSHR- value in m of slurry at Qc is then calculated as follows ... 

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