Evolution of a thermal plume in a thin vertical layer

An experimental investigation of the propagation of a thermal plume in a thin liquid layer under the influence of a point heating from below is carried out. The temperature field was visualized using an IR camera. The distribution of heat on the interface between salt glass and fluid was measured. Stages of the evolution of the thermal plume are described. A qualitative agreement with the known mechanism of motion of an axisymmetric plume was shown. The influence of a warm heat source on the speed of the thermal wave front was investigated. The necessity of taking into account this effect in the case of the slow development of the plume the duration of which exceeds the relaxation time of the heater by several times is noted. We have obtained the power law connecting the velocity of the wave front and effective heat output. The results are compared with experimental works of other authors, as well as with the proposed theory for the motion of the wave front away from the heat source and boundaries of the cavity. It is shown that the propagation velocity of the thermal front in a thin layer has a substantially lower rate in the absence of its lateral boundaries.