Three-dimensional structure of turbulent flow in mixing T-junction

Experimental results on the turbulent mixing of hot and cold airflows in a T-junction are reported, which simulates the HVAC unit used in an automobile air conditioning system. Experiments are conducted keeping Reynolds number and temperature of the main flow at 2.5 x 10(4) and 12 degrees C, respectively, and the velocity of the branch flow (60 degrees C) is changed for three velocity ratios of 0.5, 1 and 2. The flow from the branch is separated at the edge of the T-junction and forms a large separation bubble. Longitudinal vortices are formed around this separation bubble, thus the flow field has a three-dimensional structure. In spite of such a complex flow field, the mean temperature in the thermal mixing layer shows quite uniform distributions in the spanwise direction, and the strong turbulence produced around the separation bubble does not work effectively to the thermal mixing of hot and cold airflows.