  The swirling secondary flow in curved pipes is studied in three-space
dimensions using a weakly compressible Smoothed Particle Hydrodynamics (WCSPH)
formulation coupled to new non-reflecting outflow boundary conditions. A
large-eddy simulation (LES) model for turbulence is benchmarked with existing
experimental data. After validation of the present model against experimental
results for a 90 grades pipe bend, a detailed numerical study aimed at
reproducing experimental flow measurements for a wide range of Reynolds numbers
has been performed for different pipe geometries, including U pipe bends,
S-shaped pipes and helically coiled pipes. In all cases, the SPH calculated
behavior shows reasonably good agreement with the measurements across and
downstream the bend in terms of streamwise velocity profiles and
cross-sectional contours. Maximum mean-root-square deviations from the
experimentally obtained profiles are always less than 1.8%. This combined with
the very good matching between the SPH and the experimental cross-sectional
contours shows the uprising capabilities of the present scheme for handling
engineering applications with streamline curvature, such as flows in bends and
manifolds.
