Engineering Marangoni Flows (EMA)

Abstract

This final report covers the work which has been carried out within the project Engineering Marangoni Flows in the period from July 1, 2009 to December 31, 2010. The project is concerned with the development of numerical methods for and the computation of flows in a non-isothermal liquid bridge. To that end the Reynolds number for the onset (critical point) of three-dimensional hydrothermal waves is computed, three-dimensional numerical simulations carried out, and the dynamics of liquid-suspended particles are studied. In particular, the influence of a coaxial gas flow on the critical point is investigated. These investigations are in support of the JEREMI experiment which is planned to be carried out onboard the International Space Station beginning in 2015. In order to investigate the various factors influencing the stability of the bassic flow, comprehensive stability boundaries have been calculated. The critical Reynolds numbers were found to strongly depend on the material and geometry parameters. In particular, a re-stabilization of the basic flow has been discovered. Therefore, it is possible that hydrothermal waves are suppressed in favor of the steady axisymmetric state even if the Reynolds number is increased. Moreover, a complex nonlinear dynamics may result. Simulations of the flow and heat transfer in the liquid bridge have been successfully carried out using three independent software packages; Fluent, OpenFOAM and Nek5000. These simulations have included modeling of the deformation of the free surface with the software package OpenFOAM using a sharp interface method. A numerical code was developed which calculates the trajectories of particles moving in the thermocapillary flow. It is of advantage to do this in the rotating frame of reference that moves with the hydrothermal wave. It was shown that the interaction between individual moving particles and the liquid–gas interface represents a very efficient mechanism to de-mix and form particle accumulation structures. The patterns found numerically are in qualitative agreement with corresponding experimental results and more importantly for the experiments supported by this work, the particle model is able to reproduce particle accumulation structures on the time scale found in other (ground based) experiments.