OpenFOAM modeling of thermal mixing in a T-junction geometry using RANS and LES models

The discussion of mixing two fluids with different temperatures in T- junction is undoubtedly one of the most important studies in the field of Computational Fluid Dynamics (CFD). In the T-junction of pipelines, there is a possibility of the unexpected failure of the pipe material because, as a rule, mixing in this form of geometry occurs turbulently with fluctuations in temperature, pressure, and velocity. The creation of cyclic thermal stresses on the walls causes thermal fatigue and as a result, is associated with the failure of the pipe material. Calculating temperature changes in the field of safety of power equipment is very important because the non-uniformity of temperature at the surface of pipelines causes serious problems. the Organisation for Economic Co-operation and Development (OECD) / Nuclear Energy Agency (NEA) has organized a benchmark study to investigate thermal fatigue damage by conducting thermal mixing tests on a T-junction. High-quality experimental data concerning hydrodynamics and heat transfer were used to validate CFD codes. In this paper, the thermal mixing test is modeled using the OpenFOAM code, in which turbulence is simulated by the Reynolds Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) models. The averaged values of temperature and velocity calculated by RANS and LES methods are close to each other in general, although the LES method predicts values that are slightly closer to experiment.