CALCULATION OF TURBULENCE-DRIVEN SECONDARY MOTION IN DUCTS WITH ARBITRARY CROSS-SECTION

Calculation methods for turbulent duct flows are generalized for ducts with arbitrary cross sections. The irregular physical geometry is transformed into a regular one in computational space, and the flow equations are solved with a finite-volume numerical procedure. The turbulent stresses are calculated with an algebraic stress model derived by simplifying model transport equations for the individual Reynolds stresses. Two variants of such a model are considered in the present study. These procedures enable the prediction of both the turbulence-driven secondary flow and the anisotropy of the Reynolds stresses, in contrast to some of the earlier calculation methods. The importance of the secondary Reynolds shear stress is stressed, but there are no reliable experimental data for this component. Model predictions are compared to experimental data for developed flow in a triangular duct and a rod-bundle geometry. The correct trends are predicted, and the quantitative agreement is mostly fair. The simpler variant of the algebraic stress model procured better agreement with measured data.