Experimental and CFD Study of a Rectangular S-Bend Passage With and Without Pressure Recovery Effects

Abstract

Flow fields in a rectangular S-bend passage were simulated to benchmark the capability of RANS based CFD in modeling such complex flow passages with/without the effects of flow diffusion over a range of Reynolds numbers from 250,000 to 430,000. Numerical results were validated against the experimental data of pressure coefficient, wall static pressure distributions, and outflow velocity contours. Parametric studies were conducted to examine the effects of inlet turbulence properties in conjunction with the use of various turbulence models (k-ε, realizable k-ε and SST k-ω). Improvements in prediction accuracies using detailed computational domains were also examined including (i) lengthened inlet section to simulate upstream flow development, and (ii) addition of downstream flow domain to better simulate flow diffusion to an ambient outlet. Altering model geometry and inlet boundary conditions along with the use of different turbulence models had minimal improvements in the simulation results. The CFD results demonstrated that the S-bend flow features and the increasing trends of pressure magnitudes with higher Reynolds numbers were reasonably simulated. Limitations in predicting the diffusing flow fields were evident with the over predictions of pressure recovery. The study also showed the better reliabilities of the k-ε model for the simulations of S-bend flow fields through the comparisons of outflow velocity profiles.