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This study presents comparative assessment of four cavitation devices (three venturis and an orifice) in terms of cavitational yield. A fourfold approach was adopted for assessment, viz. CFD simulations of cavitating flow, simulations of individual cavitation bubble dynamics, high speed photographs of cavitating flow and model reaction of potassium iodide oxidation. Influence of design parameters of cavitation devices on nature of cavitation produced in the flow was studied. Number density of cavitation bubbles in the flow and interactions among bubbles had critical influence on cavitation yield. Orifice gave the highest cavitational yield per unit energy dissipation in flow (despite lower working inlet pressure) due to low density of cavitation bubbles in flow. On contrary, occurrence of large cavitation bubble clouds in venturi flow had adverse effect on cavitational yield due to high interactions among cavitation bubbles resulting in interbubble coalescence and recombination of oxidizing radicals generated from cavitation bubbles. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4705–4716, 2017

This work presents CFD-based optimisation of the important geometrical parameters of a cavitating venturi. The parameters for optimisation were selected based on the analysis of the steps involved in the cavitation process like cavity inception, cavity growth, and cavity collapse. It was seen that the ratio of the perimeter of the venturi to the cross-sectional area of its constriction quantifies the possible location of the inception of the cavity. The ratio of the throat length to its height (in the case of a slit venturi) controls the maximum size of the cavity and the angle of the divergence section controls the rate of collapse of a cavity. Based on the numerical study, it was concluded that a slit venturi (˛= 2.7) with the slit length equal to its height (1:1) and a half angle of divergence section of 5.5 • is an optimum geometry for best cavitational activity.Ce travail présente l'optimisation CFD-basée des paramètres géométriques importants d'un venturi cavitation. Les paramètres d'optimisation ontété choisis basés sur l'analyse desétapes impliquées dans le processus de cavitation comme la création de cavité, la croissance de cavité et l'écroulement de cavité. On l'a vu que le rapport du périmètre du venturià la section transversale de sa constriction (˛) quantifie l'emplacement possible de la création de la cavité. Le rapport de la longueur de gorgeà sa hauteur (dans le cas d'une fente venturi) contrôle la taille maximale de la cavité et l'angle de la section de divergence contrôle la vitesse de l'écroulement d'une cavité. Basé sur l'étude numérique, on a conclu qu'une fente venturi (˛= 2,7) avec la longueur de la fenteégaleà sa hauteur (1:1) et un demi-angle de la section de divergence de 5,5 est une géométrie optimum pour la meilleure activité de cavitation.

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