Investigations on mixing phenomena in single-phase flows in a T-junction geometry

Being of importance for thermal fatigue problems in nuclear power plants, turbulent mixing phenomena have been investigated in a T-junction of 50 mm pipes. As a generic case study, demineralised and tap water at room temperature and atmospheric pressure are mixed at the T-junction. The mixing pattern downstream of the T-junction is examined by two 16×16 electrode wire-mesh sensors on the basis of the difference in liquid conductivities. A dimensionless mixing scalar (concentration) distribution over the sensor plane is obtained with high time and spatial resolution. Experiments in different configurations with respect to the sensor positions, position of the tap and demineralised water inlet and for a range of combinations of the flow rates in the run and branch pipe have been carried out. Placing two sensor right behind each other in the mixing region, flow velocity measurements are also possible by correlating the sensor signals. The experiments are accompanied by numerical simulations using the code CFX-10 based on Reynolds-averaged modelling. The phenomenology of the mixing phenomena is well reproduced by the simulations, when the SST turbulence model is employed. Reasonably good quantitative agreement is obtained as well.