Calculation of turbulence-driven secondary motion in ducts with arbitrary cross-section

Abstract

Calculation methods for turbulent duct flows are generaliied for ducts with arbitrary crosssections. 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. Model predictions are compared to experimental data for developed flow in triangular duct, trapezoidal duct and a rod-bundle geometry. The correct trends are predicted, and the quantitative agreement ia mostly fair. The simpler variant of the algebraic stress model procured better agreement with the measured data.

Supersonic Corner Flow Predictions using the Quadratic Constitutive Relation

“…While corner flows are relatively weak, being only 1 -3% of the freestream velocity, they have a significant effect on wall shear stress and heat transfer in the corner. 2 For external corners, such as the junction between a wing and fuselage, this results in interference drag. 3 In internal flows, such as rectangular ducts and isolators, corner flows significantly distort the primary flow field, 4 which may lead to "unstart" conditions in airbreathing engine flowpaths.…”

Secondary Flow in Semi-Circular Ducts

“…Speziale also proved why ordinary twoequation turbulence models cannot show secondary flow, while second-order closure models can. Hurst and Rapley [15], Demuren [16] and Aly et al [17] experimentally examined turbulent flow in triangular geometries. Aly et al also performed simulations which they validated with their own experimental results.…”

Reynolds-Stress Model Prediction of 3-D Duct Flows

“…2, p. 671] at station A located at x = −R CSGA (centerline and cross-section evolution starts at x = 0, half a diameter downstream; Figs. 16,17), with computational results (grids Tab. 2) using the GLVY RSM [23], the GV RSM [32], the WNF-LSS RSM [24] and the LS k-ε [47].…”

“…Contrary to turbulence-driven secondary flows [6, Prandtl's second kind], pressuredriven secondary flows [6, Prandtl's first kind] are generally much stronger [16]. In the C-to-R transition duct studied by Davis and Gessner [14], the curvature of the walls in the transition part of the duct induces pressure-gradients in the crossflow plane yz [14, Fig.…”