Fluid manipulation and control is crucial for space exploration. Motivated by the “Thermocapillary-based control of a free surface in microgravity" (ThermoSlosh) experiment (Salgado Sánchez et al. in Acta Astronautica 205:57–67, 2023), we conduct here a detailed numerical analysis of interfacial dynamics in a two-dimensional cylindrical cell, half-filled with different silicone oils or a fluorinert, and subjected to thermal forcing and vibrations. The effect on the free surface dynamics of the applied temperature difference, vibrational amplitude, fluid viscosity, and contact angle is analyzed; both static and dynamic contact angle models are considered. Results strongly suggest that thermocapillary flows can be used to control the interface orientation within the cell, while supplemental vibrations can be added to increase the system responsiveness. This control can be further improved by using classical proportional-integral-derivative feedback to adjust the cell boundary temperatures in real-time. The proportional and derivative gains of the controller can be selected to optimize the stabilization time and/or energy cost, while the integral contribution is effective in reducing the steady-state error. Overall, the present analysis highlights the potential of using the thermocapillary effect for fluid management in reduced gravity, and evaluates different types of experimental tests that can be executed in the frame of the ThermoSlosh microgravity project.

Direct simulations on the dynamics of a liquid film coating on the outer surface of a vertical fiber are performed in the present paper. A domain mapping technique has been used on solving the Navier-Stokes problem in stream function form and predicts the dynamics of the various flow regimes with remarkable accuracy. We investigated the morphologies that develop in the coating flow down fiber and analyze the effects of Bond number and fiber diameter on the maximum liquid film height and drop speed. The results showed that the Bond number and fiber diameter have a significant effect on the instability. The transition between the Plateau-Rayleigh and convective regimes occurs at the conditions when the flow transitions from absolutely to convectively unstable.

A three-dimensional (3D) numerical simulation of a two-phase flow liquid/liquid is performed in a rectangular microchannel with a T-junction. The volume of fluid (VOF) method was used under ANSYS Fluent to capture the interface between the two phases. The dynamic mesh adaptation technique together with the assumption of symmetry plane helps us to reduce the computational cost. The study focuses on the flow patterns and hydrodynamics of plugs. So, the influence of the flow rate ratio $$q$$ , the capillary number $$Ca$$ , and the viscosity ratio on the liquid film, the plug/droplet shape, and velocity are examined here. Particularly, the plug/droplet lengths predicted by the simulation show good agreement with the experimental and correlation available in the literature. The results revealed six distinct flow patterns by dispersing water in a continuous phase of silicone oil. By decreasing the flow rate ratio as well as the viscosity ratio, the liquid film thickness increases in the corners and side planes. In turn, this greatly impacts the liquid film velocity and the plug velocity. Furthermore, capillary number (based on two-phase flow velocity) is also shown to have a greater impact than viscosity ratio and flow rate ratio on plug shape, with the curvature radii of the tail always larger than the front one.

In this paper, an electrodynamic levitation gravity compensation system based on a new type of annular Halbach array permanent magnet is proposed. The magnetic levitation force model is established using the equivalent expansion method, and the reliability of the model is verified by comparing the results of numerical calculation and simulation analysis. Through magnetic field simulation experiments, the effects of rotating speed and air gap on magnetic levitation force and eddy current loss are analyzed. The control model of the electric magnetic levitation system considering the vertical speed is investigated, and the hybrid control method of force and position is used to realize the stable magnetic levitation control. Finally, an experimental platform is built to verify the feasibility of the electric magnetic levitation system. The results show that the magnetic levitation force can be improved and the eddy current loss can be reduced by setting the rotating speed and air gap reasonably.