Cavitation causes

High water velocities can result in erosion or corrosion due to the abrasive action of particles in the water and the breakdown of the protective film which normally forms on the inside surface of the pipe. Erosion can also result from the formation of flash steam and from cavitation caused by turbulence. Publishing data on limiting water velocities are in conclusive. Table 27.9 summarizes the available information. 

Cavitation caused by homogeneous nucleation at temperatures lower than the superheat limit. 

Cavitation caused by ultrasound-triggered destruction of gas pockets in ultrasound-responsive liposomes bubbles increases the permeability of cells and tissues, thus facilitating the transport of the drug or gene into the targeted cells and tissues. 

Erosion corrosion caused by high velocity flow, fretting caused by vibration of two surfaces in close contact, and cavitation caused by very high flow... 

Cavitation causes high noise levels and severe vibration. It can be suppressed [90] by the following methods ... 

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 often occurs in hydrodynamical equipment. Our research is concerned about cavitation near ship propellers. Here cavitation causes erosion, lift oscillations and sound. The purpose of our research is eventually to find scaling rules for the sound emission of propeller models to full scale noise. Several types of cavitation can be distinguished, see for example Knapp, Daily and Hammitt [ 1]. The occurence of those types depends on, for example, the cavitation number, free stream velocity and the angle of incidence. Here a division as scotched in figure 1 will be given. 

It is expected from experimental research that sheet-cloud cavitation causes most of the sound production by a cavitating ship propellor. Therefore Omta [ 2] analysed the sound production of a spherical bubble cloud analitycally. At MARIN the results of Omta where verified in a water tunnel [3]. In these experiments the sound radiation of a bubble stream, injected into the fluid near a two dimensional hydrofoil, was measured. These bubbles where injected both intermitted and continouosly, in order to distinguish a cloudy bubble stream and a continuous bubble stream. The remarkable result of this research was that no difference between the two, above mentioned, situations was observed. 

Reduced effectiveness of pumps and tanks (cavitation causes problems in metering accurately)... 

Velocity effects include erosion-corrosion, a form of attack caused by high velocity flow cavitation caused at even higher flow by the collapse of bubbles formed at areas of low pressure in a flowing stream and fretting that is caused by vibratory relative motion of two surfaces in close contact under load erosion-corrosion, cavitation, fretting). 

Figures 17.11-17.13 present the elimination process of these floccules on LiCo02 surface with ultrasonic-assisted hydrothermal method. According to analysis of products [53, 78,79], cavitation caused by ultrasound in hydrothermal environment cannot only lead to the production of free radicals but also the occurrence of microstreaming. The former can promote organic degradation, and the latter is able to accelerate the heat and mass transfer process accompanying the renovation process. Shock waves from cavitation in liquid-solid slurries produce high-velocity inter-particle collisions. Therefore, the agglomerates on the surface of the LiCo02 can easily be broken.

---