Analysis of flow instabilities in convex and concave floating zones heated by an equatorial ring under microgravity conditions

The fluid-dynamic environment that occurs inside the melt is very sensitive to the geometrical aspect ratio AF (length/diameter) of the floating zone and to the volume factor S (ratio of the volume of the liquid zone and the volume of the corresponding cylindrical configuration: convex S>1, concave S<1). The role played by the geometrical constraints and degrees of freedom of the Marangoni toroidal rolls in determining the azimuthal structure and the stability of the flow field is discussed.