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ON THE ROLE OF INFLOW TURBULENCE FOR MIXING IN A T-JUNCTION

Eric Severac
Institute of Fluid Mechanics, Dresden University of Technology,George-Bähr-Str. 3c, D-01062, Germany

Robert Schadwill
Institut fur Stromungsmechanik Technische Universitat Dresden George-Bahr-Str. 3c 01062 Dresden, Germany

Jochen Frohlich
Institute for Technical Chemistry und Polymer Chemistry University of Karlsruhe; Institute of Fluid Mechanics, Dresden University of Technology, George-Bähr-Str. 3c, D-01062, Germany

Résumé

Large Eddy Simulations are performed in a T-junction to analyze the influence of the turbulence level of the inlets on the thermal mixing inside the pipe in the framework of predicting the thermal fluctuations acting on the pipe walls due to turbulent mixing. The Smagorinsky model and the simplest temperature model are tested an a coarse mesh against existing experimental data. The influence of the turbulence is then investigated at lower Reynolds number with four simulations featuring a block profile at the two inlets, two fully turbulent pipe flow from separate "precurssor" simulations, one block profile for the main inlet and one precursor for the side inlet, and vice versa. It results that the turbulence level at the inlets has little influence on the mean flow in the core of the pipe, but a major inlfuence on the turbulence level close to the walls and inside the recirculation zone. This modify greatly the mixing process, changing the position of the mixing zone in the radial direction, and the global temperature mixing in the cross section. It is also to be reported that the two inlets do not have the same influence and the mixing process is accelerated when the side inlet is more turbulent than the main inlet.