ON THE THERMOCAPILLARY MOTION OF DROPLETS UNDER REDUCED GRAVITY

Surface tension driven motion of liquid droplets in a liquid matrix possessing a temperature gradient is demonstrated in a near gravity-free environment. The experiment was performed in a sounding rocket providing approximately 7 min of reduced gravity. It is shown that the droplet velocity increases with the droplet size as was suggested by a linearized analysis of N. O. Young, J. S. Goldstein, and M. J. Block (J. Fluid Mech. 6, 350 (1959)). The results are discussed in view of a numerical model, which takes the nonlinear terms of the governing equations into account. For the case of creeping flow and negligible convective heat transport, i.e., for vanishing Reynolds and Peclet numbers, the numerical model has been confirmed by the result of Young et al. Comparison between theory and experiment indicates that the predicted droplet speed values are too high. Possible tentative reasons for this discrepancy are discussed. © 1991.