3D Unsteady RANS Computation of the Mixing on a T-junction


Turbulent mixing is a very common phenomenon in industrial processes. It is well know that the turbulence model has a massive impact on the accuracy of a turbulent flow, principally when it is used in processes of turbulent mixing. For this reason, this paper aims to investigate the impact of two specific turbulence models on calculating a mixture of gas-gas, using a 3D T- junction geometry. The differences between the calculation with two RANS based model, the kw-SST and SAS are investigated here. A mixture of Air and N2  is performed. The sensibility of the refinement of the mesh of calculation is assessed to calculate the discretization error. A comparison of results obtained with the distinct models of turbulence is made with available experimental data. In this comparison it is showed that the SAS model, due to its capability of capturing some vortexes that SST couldn’t, offers a better accuracy, with an error maximum bellow the 7%, in comparison to the experimental data.

Keywords: T-juntion, Turbulent mixing, RANS, CFD

[1] E. L. Paul, Atiemo-Obeng and S. M. Kresta, Handbook of Industrial Mixing - Science and Pactice, Jihn Wiley Sons, 2003.

[2] M. Mory, “Micromixing and Macromixing,” John Wiley and Sons, 2011.

[3] J. Ottino, “Mixing, chaotic advection, and turbulence,” Annual Review of Fluid Mechanics, vol. 22, pp.207-253, 1990.

[4] P. J. Ortwerth, “Mechanism of mixing of two nonreacting gases,” 1971.

[5] J. Tu, G. H. Yeoh and C. Liu, Coputational Fluid Dynamics: A practical approach, Elsevier, 2008.

[6] S. Cândido, J. Páscoa, A. Tomé, A. Amorim and S. Weber, “CFD ANALYSIS OF FLOWSTRUCTURES IN A MIXING CHAMBERA,” in Internacinal Mechanical Engineering Congress and Exposition IMECE, USA, 2019.

[7] I. ANSYS, “Fluent Theory Guide,” 2013.

[8] F. R. Menter, “American Institute of Aeronautics and Astronautics,” Two-equation eddtviscosity turbulence models for engineering aplications, pp. 1598-1605, 1994.

[9] F. R. Menter, “Two-equation eddy-viscosity turbulence models for engineering aplications,” American Institute of Aeronautics and Astronautics, vol. 32, pp. 1598-1605, 1994.

[10] F. Menter and Y. Egorav, “A scale-adaptive simulation model using two-equations models,” Aerospace Sciences Meeting and Exhibit, vol. 43, 2005.

[11] J. B. W. Kok and S. van der Wal, “Mixing in T-junction,” Appl. Math Modelling, p. 20, 1996.

[12] I. B. Celik, “Procedure for Estimation and Reporting of Discretization Error in CFD Applications,” Journal of Fluids Engineering Editorial Policy.