Laminar starting plume temperature field measurement

The temperature field of an axisymmetric laminar starting plume was measured for the first time, using an interferometric measurement technique and Abel inversion data reduction. The measurements revealed that the column of buoyant fluid following the cap has almost the same temperature distribution as the steady plume, confirming an aspect of Turner's model of the starting plume cap for the laminar case. Besides the temperature peak on the axis corresponding to the steady plume peak, an off-axial peak in the middle of the cap and an unexpected axial peak near the cap leading edge were observed. The former peak is a result of the entrained ambient fluid while the latter is unexplained but is probably associated with the instability previously observed. Temperature gradients near this peak, are estimated to be as high as 20°C/mm.