Mathematical models for sonochemical effects induced by hydrodynamic cavitation #20

Abstract

Hydrodynamic cavitation has emerged as a potential alternative for acoustic cavitation. Extensive research in past two decades has demonstrated the efficacy of hydrodynamic cavitation for enhancement of numerous physical/chemical processes. Proper design and scale-up of the hydrodynamic cavitation reactors require deep mechanistic insight into the physics/chemistry of radial motion of cavitation bubble (or cavitation bubble dynamics) that leads to generation of the sonochemical effects. Development of mathematical models for bubble dynamics in hydrodynamic cavitation is therefore a crucially important component of efficient design of hydrodynamic cavitation reactors. In this chapter, a review of the developments of mathematical models for the hydrodynamic cavitation by our research group has been given. This chapter essentially presents a summary of five major studies published by our group, in which models for radial motion of cavitation bubbles in hydrodynamic cavitation were developed with successive incorporation of various physical aspects such as liquid compressibility, turbulent pressure fluctuations, bubble/bubble and bubble/flow interactions, and heat and mass transfer across bubble interface. Simulations of hydrodynamic cavitation carried out with these models have indicated relative influences of different design and process parameters on the radial motion of the bubbles. These models have helped in the identification of the conditions under which the radial motion in hydrodynamic cavitation resembles the one observed in acoustic cavitation. The major factor governing production of sonochemical effect by cavitation bubbles is pressure recovery profile, which in turn is influenced by three design and process parameters, viz., recovery (or discharge) pressure, permanent pressure head loss, and cavitation number. The simulations of hydrodynamic cavitation have also provided suitable guidelines for design, optimization, and scale-up of the hydrodynamic cavitation reactors for applications in different physical/chemical processes. This chapter is expected to be a useful source of collective information and critical analysis of the mathematical models for hydrodynamic cavitation to the research community in the field of hydrodynamic cavitation.