T型管在工業工程中被廣泛應用。為認識T型管冷熱流體混合的相關機理，以國立清華大學T型管裝置為類比物件開展了數值研究。通過使用大型商業CFD軟體Fluent，模擬T型管內的冷熱流體在不同流速比下熱混合和熱振盪現象，分別使用穩態RANS湍流模型模擬流體熱混合特性，和使用瞬態LES分析熱振盪的頻率特性。通過模擬研究發現，不同流速比下T型管內流體呈現出不同流態，在支主管流速比較大的情況下，T型結處會發生回流現象；揭示了不同管路佈置(下游帶彎管)對T型管下游溫度波動的持續的影響。類比結果與實驗資料符合良好。

T-junctions are widely used in engineering. Based on experiments already done by NTHU, this research continue to use the commercial CFD software, Fluent ,to simulate the phenomenon of thermal mixing and thermal stripping of fluids with different temperature in T-junction at different flow rates. The steady state turbulence model RANS is used to simulating the flow characteristics of thermal mixing, and the unsteady state turbulence model LES is used to analyze the frequency characteristics of thermal stripping. It is found that the fluid in the T-junction exhibited different flow pattern at different flow ratios. Under the condition that the flow rate of the branch pipe to main pipe is relatively large, reverse flow occurs at the T-junction. The simulation results presented in average temperature are in good agreement with experimental data. The simulation also reveals that downstream elbow has a constant influence on temperature fluctuation downstream of the T-junction by swirling the fluid ,which is also called Dean vortex.

[1] E. Merzari et al., "Large-scale large eddy simulation of nuclear reactor flows: Issues and perspectives," Nuclear Engineering and Design, vol. 312, pp. 86-98, 2017.
[2] H. Ayhan and C. N. Sökmen, "CFD modeling of thermal mixing in a T-junction geometry using LES model," Nuclear Engineering and Design, vol. 253, pp. 183-191, 2012.
[3] V. S. Naik-Nimbalkar, A. W. Patwardhan, I. Banerjee, G. Padmakumar, and G. Vaidyanathan, "Thermal mixing in T-junctions," Chemical Engineering Science, vol. 65, no. 22, pp. 5901-5911, 2010.
[4] C. H. Lin and Y. M. Ferng, "Investigating thermal mixing and reverse flow characteristics in a T-junction using CFD methodology," Applied Thermal Engineering, vol. 102, pp. 733-741, 2016.
[5] J.-p. Simoneau, J. Champigny, and O. Gelineau, "Applications of large eddy simulations in nuclear field," Nuclear Engineering and Design, vol. 240, no. 2, pp. 429-439, 2010.
[6] S. Chapuliot, C. Gourdin, T. Payen, J. P. Magnaud, and A. Monavon, "Hydro-thermal-mechanical analysis of thermal fatigue in a mixing tee," Nuclear Engineering and Design, vol. 235, no. 5, pp. 575-596, 2005.
[7] L. W. Hu and M. S. Kazimi, "LES benchmark study of high cycle temperature fluctuations caused by thermal striping in a mixing tee," (in English), International Journal of Heat and Fluid Flow, vol. 27, no. 1, pp. 54-64, Feb 2006.
[8] J. I. Lee, L.-w. Hu, P. Saha, and M. S. Kazimi, "Numerical analysis of thermal striping induced high cycle thermal fatigue in a mixing tee," Nuclear Engineering and Design, vol. 239, no. 5, pp. 833-839, 2009.
[9] H. Kamide, M. Igarashi, S. Kawashima, N. Kimura, and K. Hayashi, "Study on mixing behavior in a tee piping and numerical analyses for evaluation of thermal striping," Nuclear Engineering and Design, vol. 239, no. 1, pp. 58-67, 2009.
[10] C. Walker, M. Simiano, R. Zboray, and H. M. Prasser, "Investigations on mixing phenomena in single-phase flow in a T-junction geometry," Nuclear Engineering and Design, vol. 239, no. 1, pp. 116-126, 2009.
[11] A. K. Kuczaj, E. M. J. Komen, and M. S. Loginov, "Large-Eddy Simulation study of turbulent mixing in a T-junction," Nuclear Engineering and Design, vol. 240, no. 9, pp. 2116-2122, 2010.
[12] S. T. Jayaraju, E. M. J. Komen, and E. Baglietto, "Suitability of wall-functions in Large Eddy Simulation for thermal fatigue in a T-junction," Nuclear Engineering and Design, vol. 240, no. 10, pp. 2544-2554, 2010.
[13] T. Frank, C. Lifante, H. M. Prasser, and F. Menter, "Simulation of turbulent and thermal mixing in T-junctions using URANS and scale-resolving turbulence models in ANSYS CFX," Nuclear Engineering and Design, vol. 240, no. 9, pp. 2313-2328, 2010.
[14] M. H. C. Hannink and F. J. Blom, "Numerical methods for the prediction of thermal fatigue due to turbulent mixing," Nuclear Engineering and Design, vol. 241, no. 3, pp. 681-687, 2011.
[15] R. Zboray and H.-M. Prasser, "On the relevance of low side flows for thermal loads in T-junctions," Nuclear Engineering and Design, vol. 241, no. 8, pp. 2881-2888, 2011.
[16] T. Ming and J. Zhao, "Large-eddy simulation of thermal fatigue in a mixing tee," International Journal of Heat and Fluid Flow, vol. 37, pp. 93-108, 2012.
[17] M. Tanaka, "Investigation of V&V process for thermal fatigue issue in a sodium cooled fast reactor – Application of uncertainty quantification scheme in verification and validation with fluid-structure thermal interaction problem in T-junction piping system," Nuclear Engineering and Design, vol. 279, pp. 91-103, 2014.
[18] K. Miyoshi, M. Kamaya, Y. Utanohara, and A. Nakamura, "An investigation of thermal stress characteristics by wall temperature measurements at a mixing tee," Nuclear Engineering and Design, vol. 298, pp. 109-120, 2016.
[19] P. Gauder, P. Karthick Selvam, R. Kulenovic, and E. Laurien, "Large eddy simulation studies on the influence of turbulent inlet conditions on the flow behavior in a mixing tee," Nuclear Engineering and Design, vol. 298, pp. 51-63, 2016.
[20] M. Draksler, B. Končar, L. Cizelj, and B. Ničeno, "Large Eddy Simulation of multiple impinging jets in hexagonal configuration – Flow dynamics and heat transfer characteristics," International Journal of Heat and Mass Transfer, vol. 109, pp. 16-27, 2017.
[21] M. Georgiou and M. V. Papalexandris, "Direct numerical simulation of turbulent heat transfer in a T-junction," (in English), Journal of Fluid Mechanics, vol. 845, pp. 581-614, Apr 27 2018.
[22] M. S. Gritskevich, A. V. Garbaruk, T. Frank, and F. R. Menter, "Investigation of the thermal mixing in a T-junction flow with different SRS approaches," Nuclear Engineering and Design, vol. 279, pp. 83-90, 2014.
[23] S. B. Pope, Turbulent Flows. 2000.
[24] S. M. Hosseini, K. Yuki, and H. Hashizume, "Experimental Investigation of Flow Field Structure in Mixing Tee," Journal of Fluids Engineering, vol. 131, no. 5, 2009.
[25] Y. Dubief † and F. Delcayre ‡, "On coherent-vortex identification in turbulence," Journal of Turbulence, vol. 1, 2000.
[26] S. M. Hosseini, K. Yuki, and H. Hashizume, "Classification of turbulent jets in a T-junction area with a 90-deg bend upstream," International Journal of Heat and Mass Transfer, vol. 51, no. 9-10, pp. 2444-2454, 2008.
[27] N. Kimura, H. Ogawa, and H. Kamide, "Experimental study on fluid mixing phenomena in T-pipe junction with upstream elbow," Nuclear Engineering and Design, vol. 240, no. 10, pp. 3055-3066, 2010.
[28] T. Lu, D. Attinger, and S. M. Liu, "Large-eddy simulations of velocity and temperature fluctuations in hot and cold fluids mixing in a tee junction with an upstream straight or elbow main pipe," Nuclear Engineering and Design, vol. 263, pp. 32-41, 2013.
[29] M. S. Gritskevich and A. V. Garbaruk, "Influence of upstream pipe bends on the turbulent heat and mass transfer in T-junctions," Journal of Physics: Conference Series, vol. 891, 2017.
[30] R. Tunstall, D. Laurence, R. Prosser, and A. Skillen, "Large eddy simulation of a T-Junction with upstream elbow: The role of Dean vortices in thermal fatigue," Applied Thermal Engineering, vol. 107, pp. 672-680, 2016.