Bubble distribution in a turbulent pipe flow

In the gas-liquid turbulent bubbly pipe flows, the prediction of the spatial distribution of the phases is crucial for the design of the thermohydraulic loops. This prediction remains difficult because of the coupled effects of the bubble drift velocity (due to gravity), the turbulence of the liquid phase, the dynamics of the bubbles and the vicinity of a wall. Up to now, no satisfactory model does exist, especially in micro gravity conditions. In order to analyse the role of the gravity and the turbulence of the liquid phase upon the bubbles distribution, experiments and numerical simulations are performed under normal gravity conditions and in micro gravity. They consist of a lagrangian tracking of single bubbles in a turbulent pipe flow. The experimental and numerical results show that, on earth, under the action of the lift force, the bubbles move radially towards the pipe wall in vertical upward flow, towards the pipe centre in downward flow. In micro gravity, in absence the drift velocity, the lift force vanishes. The action of the large turbulent eddies is dominant on the bubble dispersion and the radial bubble distribution is more homogeneous.