RANS SIMULATIONS OF TURBULENT AND THERMAL MIXING IN A T-JUNCTION

Abstract

The turbulent and thermal mixing in a horizontally oriented T-junction is investigated numerically. The objective of the present study is to determine the mixing length in a T-junction where homogeneous temperature distribution is established in the cross section. A steady state three-dimensional turbulent flow is considered with a Reynolds number of 0.7 × 10⁵ at the inlet of the main cold pipe. Grid is generated in a stretched manner so that strong gradients near the wall regions are accounted for as required. Four turbulence models are tested to provide closure for the Reynolds stress tensor: the k-ε standard, the
k-ω standard, the k-ω SST and the RSM models. For all simulated cases, good qualitative agreement is obtained. Quantitative comparisons show that the standard k-ε and the RSM models give too low or high predictions, whereas both k-ω models are reasonably close between them. It is found that a length of 80 inch is enough to get homogenous temperature if a tolerance of 1°C is considered. Further simulations on a longer pipe are strongly encouraged to assist in elucidating the length mixing determination.

DOI: http://dx.doi.org/10.5755/j01.mech.19.3.4663