An investigation on the bubbly flow of a Venturi channel based on the population balance model

Abstract

AbstractIn this paper, the bubbly flow characteristics of a Venturi channel was revealed by using the population balance model (PBM) within the framework of computational fluid dynamics (CFD) numerical simulation and focused on the bubble size distribution and pressure drop △P of different regions. The simulation results indicated that bubble breakup mainly occurred in the diverging section of the Venturi channel, and the average diameter of the daughter bubbles davg in the sidewall region was much smaller than that in the central region. Through the correlational analysis between the bubble size distribution and turbulent flow field, the bubble breakup in the diverging section was positively related to the turbulent flow. Considering the influence of geometric parameters on davg and △P, the davg decreased and △P increased with the increasing of the diverging angle β. As the throat diameter D increased, the davg increased and △P decreased gradually. In order to quantify the bubble breakup characteristics, the concept of bubble breakup ratio τ is introduced and defined as the ratio of inlet average bubble diameter di to the outlet average bubble diameter do. Through dimensionless transformation, the fitting relationship between τ or △P and angle ratio a was Sinusoidal function (SINE), respectively, and was Boltzmann with the throat length‐diameter ratio b. Due to the relationship of first‐order linear function between τ and △P, the bubble breakup ratio can be obtained by measuring the pressure drop of the Venturi tube, which was significant to the practical engineering application.