Events

Two Phase Flows with Complexities

Date: Thursday 12 July 2018 14:00 - 15:00

Location: ENG324, SEMS, QMUL

Real two-phase flows can be much affected by departures from the basic model of two-phase flows that is commonly used (incompressible flows of perfectly clean fluids, without contact lines). This gives the potential of controlling flows, but may also be a concern if such "complexities" arise in applications and their effects are not known. In this seminar an overview is presented of computational studies of the effects of complexities, including contact lines, the presence of surfactants, and compressible two-phase flows. Often, computational methods are not available, and have to be developed as a secondary aim.
For flows with moving contact lines, the challenge faced is to develop a computational model that can be used for a broad range of flows, in 3D. To use coupling with theory in numerically unresolved region around a contact line requires is shown to give satisfactory results, but further work is needed to extend the existing theory, which is too limited.
Flow regime boundaries can be affected by surfactants, but not much is known about this generally. Much experimental evidence is available for sheared foams, wherein surfactants are used to stabilize a dense suspension of bubbles, but exactly how that works is not known. For this purpose we have numerically simulated a simple 2D model problem. Although a simple interface rheology was used, and under highly idealized conditions at that, the effective rheology of the suspension showed an interesting result regarding the role of work done through Marangoni stresses.
Next, an outline of current work on compressible two-phase flows, including collapsing bubbles and shock/bubble interactions. Most of the existing computational methods are for inviscid systems without thermal conduction, whereas these can play a role in applications. A computational method has been developed for the full compressible Navier-Stokes equations, and test results will be presented at the seminar.
The talk is concluded with an overview of some further activities, including transport of a passive scalar in two-phase flow and the instability of pressure-driven two-layer channel flows.

References
contact lines: Solomenko et al., J. Comput. Phys. 2017
surfactants: Titta et al., J. Fluid Mech. 2018
compressible flows: Capuano et al., J. Comput. Phys. 2018
passive scalars in bubbly flows: Loisy et al. J. Fluid Mech. 2018
instability of two-layer flows: O Naraigh & Spelt J. Fluid Mech. 2018.