| Microgravity conditions pose unique challenges for fluid handling and heat transfer applications. By controlling (curtailing or augmenting) the buoyant and thermocapillary convection, the latter being the dominant convective flow in a microgravity environment, significant advantages can be achieved in space based processing. The control of this surface tension gradient driven flow is sought using (1) rotation and (2) magnetic field, and the effects of these are computationally studied in two separate parts. In the first part, the main parameters are the solutal Marangoni number Mc, representing the surface tension gradient force and the Taylor number Ta representing the rotational effect. For given values of Mc, certain values of Ta were detected where the Sherwood number Sh, representing the convective solute flux, and the convective flow effects are noticeably reduced. These results can provide conditions under which convective flow transport approaches the diffusion limited transport, which is desirable, for example in the production of higher quality protein crystals. In the second part, a two-fluid layer system, with the lower fluid being a non-conducting ferrofluid, is considered under the influence of a horizontal temperature gradient. To capture the deformable interface, a numerical method to solve the Navier-Stokes equations, Heat equations and Maxwell's equations was developed using a hybrid Level Set/Volume-of-Fluid technique. The convective velocities and heat fluxes were studied under various regimes of the thermal Marangoni number Ma, the external field represented by the magnetic Bond number Bom, and various gravity levels, Fr. Regimes where the convection were either curtailed or augmented were identified. It was found that the surface force due to the step change in the magnetic permeability at the interface could be suitably utilized to control the instability at the interface. |
