Convection In Gallium Research Articles

Natural Convection of a Liquid Metal in Vertical Circular Cylinders Heated Locally From the Side

An experimental study is made of natural convection in gallium melts enclosed by vertical circular cylinders with localized circumferential heating. Heating is done in an axial band at the mid-height, and both ends of the cylinder are cooled. In the present study, the cylinder aspect (Ar = height/diameter) ratio ranges from 2 to 10, and the Rayleigh number (Ra) ranges from 9.0 × 104 to 3.0 × 107. The Prandtl number is 0.021. Temperature measurements are made at six axial levels around the circumference of the cylinder to study thermal convection in the melt. A numerical analysis is also conducted to supplement the experimental information. When Ra is small, the melt is in steady toroidal motion. Above a certain Ra, the flow becomes nonaxisymmetric as a result of a thermal instability, in the case of Ar larger than 3. With increasing Ra, the motion becomes oscillatory, mainly in the upper half. When Ar is smaller than 3, the toroidal flow becomes nonaxisymmetric and oscillatory at the same time beyond a certain Ra. The conditions for the appearance of oscillations and the oscillation frequencies are investigated in detail.