Study on convective mixing for thermal striping phenomena (Experimental analyses on mixing process in parallel triple-jet and comparisons between numerical methods)

A quantitative evaluation on the thermal striping, in which temperature fluctuation due to convective mixing imposes thermal fatigue on structures, is of importance for reactor safety. As for convective mixing, a water experiment was performed on vertical, parallel triple-jet: a cold jet at the center and hot jets in both sides. Three kinds of calculations based on the finite difference method for the experiment were carried out. Two types of turbulence models were used in the calculations, namely k-epsilon two-equation turbulence model (k-epsilon Model) and low Reynolds number turbulence stress and heat flux equation models (LRSFM). Furthermore, a quasi-direct numerical simulation (DNS) was performed. The DNS could simulate the time-averaged temperature field. The prominent frequency in temperature fluctuation obtained by the LRSFM was in good agreement with that in the experiment. The profile of power spectrum density of temperature fluctuations calculated by the DNS was close to the experimental results.