Experimental study on the evolution of a thermally forced convective boundary layer through 3D PTV and temperature measurements

Transport and mixing features of stratified fluids while free convection occurs are investigated by means of a laboratory model. The experimental apparatus is designed for simultaneously providing temperatures through thermocouples and Lagrangian particle trajectories by using a fully three dimensional image analysis technique (3D Particle Tracking Velocimetry). Characteristic structures have been observed in the convective boundary layer: growing domes, flat regions of large horizontal extent, and cusp-shaped regions of entrainment. Dome characteristic dimensions are of the same order of magnitude as the mixing layer height, while their lifetime is less or equal to the time a fluid particle would need to complete a whole cycle moving through the rising dome and returning in the down-welling region. The comparison with literature data shows a good agreement with measurements taken both at bench and real scale, demonstrating the applicability of laboratory investigation for the atmospheric boundary layer monitoring.