Numerical Investigation on Turbulence and Bubbles Distribution in Bubbly Flow Under Normal Gravity and Microgravity Conditions

Abstract

Two-phase flows of gas and liquid are increasingly paid much attention to space application due to excellent properties of heat and mass transfer, so it is very meaningful to develop studies on them in microgravity. In this paper, gas-phase distribution and turbulence characteristics of bubbly flow in normal gravity and microgravity were investigated in detail by using Euler-Lagrange two-way model. The liquidphase velocity field was solved by using direct numerical simulations (DNS) in Euler frame of reference, and the bubble motion was tracked by using Newtonian motion equations that took into account interphase interaction forces including drag force, shear lift force, wall lift force, virtual mass force and inertia force, etc. in Lagrange frame of reference. The coupling between gas-liquid phases was made with regarding interphase forces as a momentum source term in the momentum equation of the liquid phase. Under the normal gravity condition, a great number of bubbles accumulate near the walls under the influence of the shear lift force, and addition of bubbles reduces turbulence of the liquid phase. Different from the normal gravity condition, in microgravity, an overwhelming majority of bubbles migrate towards the centre of the channel driven by the pressure gradient force, and bubbles have little effect on the turbulence of the liquid phase.

Numerical Investigation on the Flow Instability of Dispersed Bubbly Flow in a Horizontal Contraction Section

“…The standard k-ω model is used for both the water and gas phases. Turbulence kinetic energy, k, and the specific dissipation rate, ω, can be calculated by solving the transport equations given in Equations ( 9) and (10):…”

“…In most cases, the bubbles that disperse in the continuous water phase vary widely in distribution, shape and size, which is known as the bubbly flow. Due to the abundant number of small bubbles, the flow mechanism of two-phase flow is much more complicated than that found in single-phase flow and includes the effects of: discontinuity of properties at the phase interface [6]; bubble merge and annihilate [7,8]; forces acting on the gas-liquid interface [9,10]; flow instability [11,12]; and bubble-induced turbulence [13,14].…”

The Nonlinear Phenomenon in Modal Analysis of Liquid Tank

“…Because the liquid can flow freely in structure, so when constrained in different location, the wet plates of tank are changed. Now, some research have pointed out that the gravity plays an important role in the vibration of structure with liquid [5][6]. So as for the liquid tank which will take nonlinear after liquid filled [7], a one-room tank and four-room tank are modeled to study the behavior of tank model when it is constrained in different location.…”