Numerical studies on bubble dynamics in an unsteady turbulence of the venturi bubble generator applied to TMSR

In the online fission gas removal system applied to TMSR, the venturi bubble generator was developed to produce the dispersed bubbles from the reactor coolant. It is essential to establish the critical condition of bubble breakup for the bubble generation. Numerical simulations of the bubble dynamics in an unsteady turbulent flow in the bubble generator are performed with Volume-of-fluid (VOF) and Large-eddy-simulation (LES). The flow fields with similar turbulent characteristics in the bubble generator are established in the cavity to track the bubble dynamics. The dynamic boundary conditions are set to simulate the bubble dynamics in the two patterns of flow including shearing flow and rotational flow. The critical Weber number of the bubble ranges from 0 to 10. Weber number is always fluctuating in a certain range before bubble breakup. The dynamic characteristics of the bubble shape factor in this complex unsteady flow can be modeled by a one-dimensional damped oscillator model. The bubble oscillation in unsteady turbulence can be predicted by combining the dimensionless number of time and the Weber number. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

This study investigated the critical breakup condition of bubbles generated by a venturi bubble generator in the online fission gas removal system applied to TMSR, and explored the bubble dynamics in unsteady turbulent flow through numerical simulations. The dynamic characteristics of bubble shape factor can be modeled by a one-dimensional damped oscillator model, and bubble oscillation in unsteady turbulence can be predicted using a combination of dimensionless time and Weber number.