Performance of eddy-viscosity turbulence models for predicting swirling pipe-flow: Simulations and laser-Doppler velocimetry

We use laser-Doppler velocimetry (LDV) experiments and Reynolds-averaged Navier--Stokes (RANS) simulations to study the characteristic flow patterns downstream of a standardized clockwise swirl disturbance generator. After quantifying the impact of the mesh size, we evaluate the potential of various eddy-viscosity turbulence models in providing reasonable approximations with respect to the experimental reference. The choice of turbulent models reflects current industry practice. Our results suggest that models from the $k$-$\epsilon$ family are more accurate in predicting swirling flows than models from the $k$-$\omega$ family. For sufficiently resolved meshes, the realizable $k$-$\epsilon$ model provides the most accurate approximation of the velocity magnitudes, although it fails to capture small-scale flow structures which are accurately predicted by the standard $k$-$\epsilon$ model and the RNG $k$-$\epsilon$ model. Throughout the article, we highlight practical guidance for the choice of RANS turbulence models for swirling flow.