Magnetic buoyancy force acting on bubbles in nonconducting and diamagnetic fluids under microgravity

Abstract

The magnetic buoyancy force acting on a bubble in a one-dimensional magnetic field can be represented as Fϭ( G Ϫ L )͐H(dH/dx)dVol B , where G and L are the volume magnetic susceptibilities of the gas and liquid, respectively, and H is the magnetic field strength. Since ͉ L ͉ ӷ͉ G ͉ and most liquids are diamagnetic, this expression indicates that the magnetic buoyancy forces act in the direction of increasing magnetic field strength. Because the magnetic buoyancy force in a diamagnetic fluid is small, the motion of bubbles under normal gravity is difficult to study, but microgravity offers the possibility of detailed observations. Using a compact permanent magnet under microgravity conditions, N 2 bubbles in pure water ͑0.01 dyne s/cm 2 ) and in a 69:31 glycerol/ water mixture ͑0.21 dyne s/cm 2 ) were found to move in the direction of increasing H, and to be held stationary at the point of maximum H. The motion of the bubbles was also simulated with a theoretical model and was found to agree with measurements made under microgravity conditions. These results indicate that magnetic buoyancy can be used to control bubble motion. Since most fluids are diamagnetic, magnetic buoyancy can be used to control bubbles in many fluidic devices used in space applications.

New opportunities in science, materials, and biological systems in the low-gravity (magnetic levitation) environment (invited)

“…͑7͒ In multicomponent fluids, or where objects may be placed in fluids, or may crystallize from solution, one must consider both differentials in susceptibility and buoyancy in determining the effective acceleration. 23,25 ͑8͒ In the bores of room temperature access, water cooled resistive and helium cooled superconducting magnets, the temperature is generally less than room temperature, and may involve substantial spatial temperature gradients. The presence of air currents, and even strong air turbulence are clearly present in many cases.…”

Lateral and Axisymmetric Ferrofluid Oscillations in a Cylindrical Tank in Microgravity

“…Magnetic polarization forces are becoming increasingly popular in space technology as a means of controlling multiphase flows in reduced gravity environments. Applications include mass transfer [1][2][3][4][5], spacecraft propulsion [6][7][8], thermomagnetic convection [9,10], phase separation [11], sample holding [12], or diamagnetically-enhanced electrolysis [13], among others. The polarization force can be induced on natural liquids and magnetically-enhanced substances, which are classified as diamagnetic, paramagnetic, or ferromagnetic.…”

Magnetic phase separation in microgravity

“…This phenomenon is known as magnetic buoyancy and has been applied to terrestrial boiling experiments with ferrofluids 37,38 . Previous works on low-gravity magnetohydrodynamics have explored the diamagnetic manipulation of air bubbles in water 39,40 , the positioning of diamagnetic materials 41 , air-water separation 42 , protein crystal growth 43 , magnetic-positive positioning 44,45 , magnetic liquid sloshing 46,47 , and combustion enhancement 40 , among others. The application of Lorentz's force on liquid electrolytes has also been studied as a way to enhance hydrogen production [48][49][50] .…”