Modulation of turbulent channel flow laden with contaminated microbubbles

Abstract

Examining the interaction between microbubbles and turbulence in vertical channel flow is done in this thesis. An Eulerian?Lagrangian approach based on pseudo-spectral direct numerical simulation is used. Babbles, due to their small size, are treated as solid spheres subject to gravity, added mass, pressure gradient, Basset, drag and lift forces, and they are momentum coupled with the fluid. A downward channel flow configuration of water at shear Reynolds number 〖Re〗_τ=360 and three different bubble diameters are considered and tested (d=110μm,220μm and 330μm) where the bubbles are considered to be non-deformable since they are of small Eotvos Eo number and with no-slip condition applies at bubble surface. As some previous studies, this examination confirms different bubbles distribution in the downflow configuration such as preventing bubbles from reaching the near-wall region. Because of the local momentum exchange with the carrier fluid as well as to the bubble distribution differences, significant decrease of both liquid flow rate and wall shear are observed. We discuss and analyze all the observed trends in this simulation.The Direct Numerical Simulation (DNS) is the mean used to study such a case. The results are compared with Kim et al. (1987) [30], which is considered as a reference to the turbulent simulation. Statistics related to velocity profile, particles profile and turbulence profile are simulated and discussed closely. This will make us try to understand the physics behind the behavior of the effect of microbubbles in a turbulent flow.