Transport characteristics of thermal plume driven by turbulent mixing in stairwell

A set of experiments was conducted to study the transport characteristics of thermal plume driven by turbulent mixing in a 1/3 scale stairwell with single opening. The opening location was varied at the stairwell height direction to obtain different air supply conditions. When the thermal plume moves upwardly in the vertical stairwell, the interface between the upper cold layer and the lower hot layer is unstable. The gravitational instability leads to the turbulent mixing in the two layers. The location of the thermal plume front is determined using the temperature increases at different measuring points. Based on the dimensional analysis, the plume front location can be expressed as a function of time and effective gravitational acceleration. The velocity of thermal plume in stairwell is lower than those in hollow shafts, resulting from the block and cooling effects of stair steps. The comparison of the experimental and calculated plume front locations shows good agreement with the maximum error less than 20%. The results could improve the understanding of thermal plume movement driven by turbulent mixing in stairwells.