Control of bubbles in fluids by using magnetic buoyancy forces

Abstract

Magnetic force, i.e., magnetization force is body force and the function of density, and it is possible to induce buoyancy and convection similarly to the gravitational one. Magnetization force under 1D magnetic field gradient is generally shown by the product of density (p), mass magnetic susceptibility (x g ), magnetic field strength (H) and its gradient (dH/dy). Several experiments to control bubbles by using magnetic buoyancy forces were conducted under microgravity as follows: (1) Magnetic transport of bubbles: In pure water and glycerol/water mixture which are diamagnetic, the magnetic buoyancy force caused by a strong permanent magnet could transport bubbles toward a stronger magnetic field and to fix bubbles at the maximum point of magnetic strength. The transporting velocity was found to decrease with decreasing the radius of bubbles and increasing the viscosity. (2) Collision and fusion of two bubbles: It is almost impossible to observe the collision of bubbles clearly on the earth. the technique of magnetic control of bubbles nd microgravity condition made this observation possible. (3) Magnetic support of chemical reaction to produce bubbles (2H 2 O 2 →O 2 +2H 2 O on Pt catalyst). When small O 2 bubbles were removed from the surface of catalyst by magnetic buoyancy force, the decomposition reaction was observe to continue smoothly even under microgravity. On the other hand, in the absence of the magnet, the reaction was observed to stop under microgravity. Thus, the present study suggest the potential of using magnetic buoyancy forces to control bubbles in space experiments.