Numerical simulation of the coherent structure and turbulent mixing in tight lattice

Abstract

The turbulent flow and transverse mixing in triangular rod bundles is investigated numerically. The calculation results were firstly validated with experimental data. Then the effects of Reynolds number, Prandtl number and pitch to diameter ratio on the coherent structure and turbulent mixing are analyzed. The coherent structure exists in a very wide range of Reynolds number in tight lattice. The effect of Prandtl number on the coherent structure and turbulent mixing is more limited than that of Reynolds number. The effect of pitch to diameter ratio on the coherent structure is most significant. The critical pitch to diameter ratio for this lattice is next to 1.03. As the pitch to diameter ratio decrease from a big number to the critical value, the coherent structure becomes more significant which is benefit to the local flow and heat transfer. But as the pitch to diameter ratio continues decreasing from this critical value to a very small value, the coherent structure becomes weaker and weaker, and the local flow and heat transfer also become more and more terrible.