Vibrational Effects on Diffusion Experiments

Main task of diffusion experiments in liquids is to avoid additional transport induced by convection. Even under microgravity conditions aboard a space vehicle, diffusion measurements can be disturbed. Additional transport due to residual accelerations and vibrations can only be analysed under low gravity conditions. For the 28th ESA Parabolic flight campaign (May 2000), modified for the 31st ESA Parabolic flight campaign (October 2001) and for the 34th ESA Parabolic flight campaign (April 2003), a model experiment using water as liquid was developed. Because of the short term of a parabola, the analogy between diffusive mass transport and the faster heat transport was used. The angle between the 4mm or 10mm thin capillary and the direction of acceleration ranged between 0∘ and 90∘. For an oscillation amplitude of 100mm, the increase of the frequency up to 1 Hz led to a slight increase of the additional transport. Experiments with 1.7 Hz showed an additional transport of maximum 50%. An effect of the angle between the capillary and the acceleration vector was in the order of the error.