COMBINED RESIDUAL NATURAL AND MARANGONI CONVECTION IN A LIQUID SPHERE SUBJECTED TO A CONSTANT AND VARIABLE MICRO-GRAVITY FIELD

The combined effect of thermal Marangoni convection induced by a gradient of temperature imposed upon the free surface of a liquid sphere and the residual natural convection stemming from the still existing micro-gravity field in an orbiting space laboratory has been investigated. The case of a constant and linearly dependent axial residual gravity field has been considered, for which the Stokes equation in the approximation of Boussinesq have been solved. By the introduction of a dynamic Bond-number derived as the ratio of the Grashof number to the Reynolds number based upon the Marangoni flow the predominance of Marangoni- or natural convection could be determined. Streamlines, radial- and angular velocity distributions have been obtained analytically. The combined effect of Marangoni- and natural convection is of importance for space processings. In addition the isothermal lines are presented for various imposed temperature distributions at the free surface of the liquid sphere.