Hydrodynamic cavitation experimental

It is always important to choose an optimum design configuration of the hydrodynamic cavitation reactor so as to maximize the cavitational effects and achieve cost effective operation. In this section, we will discuss available reactor configurations and give some guidelines, based on theoretical analysis coupled with experimental results, for selection of optimum design and operating parameters for hydrodynamic cavitation reactors. 

Fig. 3.4 Schematic representation for experimental setup for the orifice plate hydrodynamic cavitation reactor...

Senthilkumar P, Sivakumar M, Pandit AB (2000) Experimental quantification of chemical effects of hydrodynamic cavitation. Chem Eng Sci 55 1633-1639... 

Mishra C, Peles Y (2006) An experimental investigation of hydrodynamic cavitation in micro-Venturis. Phys Fluids 18 103-109... 

The second contribution, written by Pareg Gogate and Anniruddha Pandit from the Institute of Chemical Technology in Mumbai, stresses important factors for efficient scaleup of cavitational reactors and subsequent industrial applications based on the theoretical and experimental analysis of the net cavitational effects. Guidelines for selection of an optimum set of operating parameters have been presented and hydrodynamic cavitation has also been discussed. 

Optimization of Hydrodynamic Cavitation Reactor Based on the Experimental... 

Combination of the hydrodynamic-cavitation reactors and sonochemical reactors where the cavity is generated using the hydrodynamic means and the collapse of the cavities is taking place in the sonochemical reactor. The distance between the two events (generation and collapse) will be a crucial design aspect in the expected synergism and should be established with theoretical simulations and/or experimental validation for a particular application. The developed reactor should be operated in a continuous mode and needs be tested for different cavitational transformations. 

Cavitation, the phenomenon that causes liquids to rupture and to form vaporous/gas cavities when subjected to sufficiently low pressures, can occur in any machine handling liquid when requisite hydrodynamic conditions develop (Fig. 1). Cavitation, in many cases, is an undesirable phenomenon in hydraulic machinery that can Umit performance, lower efficiency, introduce sever structural vibration, generate acoustic noise, choke flow, and cause catastrophic damage [1]. The pernicious effects of hydrodynamic cavitation on conventional fluid machinery have been recognized and actively researched in the last century. Present knowledge (experimental and analytical) of cavitation has contributed immensely toward improving the design of conventional-scale fluid machinery. 

The high temperatures and pressures created during transient cavitation are difficult both to calculate and to determine experimentally. The simplest models of collapse, which neglect heat transport and the effects of condensable vapor, predict maximum temperatures and pressures as high as 10,000 K and 10,000 atmospheres. More realistic estimates from increasingly sophisticated hydrodynamic models yield estimates of 5000 K and 1000 atmospheres with effective residence times of <100 nseconds, but the models are very sensitive to initial assumptions of the boundary conditions (30-32). 

The prediction of the inception of cavitation is, of course, closely related to nucleation theory, but has generally been studied experimentally by modeling with reference to the hydrodynamic flow field (El, L7, S15). The usual criterion is the Prandtl cavitation number (M6),... 

Explosion hydrodynamics is related to the investigation of a wide range of unsteady processes developing under pulse loading of liquids, such as wave processes, bubble cavitation and high-rate cumulative jet flows. These phenomena are possible to be analysed in detail only by the combined investigations, both experimental and theoretical, with developing appropriate physical and mathematical models. This approach will be demonstrated below on the examples of some principal results and will refer mainly to the so-called surface effects and the problem of wave field parameters control. 

This paper presents the results of a theoretical study of the oil film forces, arising from combined hydrodynamic squeeze and wedge actions, in a dynamically loaded bearing. In particular, it shows how the non-linearity of the force-journal velocity relationship is dependent upon cavitation. Simple equations for the total oil film force components, at any given eccentricity ratio, are fitted to the predicted force-velocity data. These equations introduce five velocity coefficients, which take account of the non-linear behaviour. Application of these equations to a fast journal orbit analysis, including comparison with experimental results, is described in reference (5). 

K. K. Shalnev, Experimental Studies of the Intensity of Erosion Due to Cavitation, in Proceedings of Symposium on Cavitation in Hydrodynamics Held at the National Physical Laboratory on Sept. H 17, 1956. London H. M. Stationery Office, 1956. (Paper 22)... 

From these theoretical considerations and the experimental investigations, it is evident that the hydrodynamic ear forces generated by microstreaming around resonant bubbles are sufficiently strong to cause degradation of very large macromolecules My, > 10 ) under conditions vdiere transient cavitation is absent. 

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