Effect of bubble size on Lagrangian pressure statistics in homogeneous isotropic turbulence

Abstract

The study of bubble's behavior in turbulent flows is fundamental to the understanding of many engineering applications that are concerned with bubbly/two-phase flow. In turbomachinery, for example, tiny gas nuclei present in the liquid may grow to macroscopic size if the instantaneous pressure dips below the vapor pressure for a time long enough to incite cavitation events. In this paper, the Lagrangian pressure statistics of finite sized bubbles in homogeneous isotropic turbulence is investigated using highly-resolved direct numerical simulations of the Navier-Stokes equations at Reλ = 150. A modified Maxey-Riley equation is used for Lagrangian tracking of bubbles in the turbulence field. The Lagrangian pressure statistics (probability density function, frequency of low-pressure events and their duration) are analyzed as functions of the bubble size. The overall picture that emerges is consistent with finite-sized bubbles being driven towards vortex cores, resulting in an average pressure further below the mean value and longer and more frequent low-pressure events as the considered size is increased.