On the use of particle-wall interaction models to predict particleladen flow in 90-deg bends

The objective of this work is to evaluate the capability of different combinations of a turbulence
model and a Lagrangian particle tracking (LPT) model integrating a particle-wall interaction (PWI)
model to predict particle-laden flow in 90-deg bends, as well as the impact of the PWI model on
the prediction of the referred flow. The experimental data from Kliafas and Holt (1987) (LDV
measurements of a turbulent air-solid two-phase flow in a 90° bend. Experiments in Fluids, 5: 73–85)
concerning a vertical to horizontal square-sectioned duct with a hydraulic diameter of 0.1 m that are
connected by a 90-deg bend with a curvature ratio of 3.52, served as the benchmark for the aimed
analysis. Air with glass spheres of 50 μm diameter flows in the experimental duct system with a
Reynolds number of 3.47×105. The airflow was modelled by four different turbulence models: a low
Reynolds number k-ε model, the SST k-ω model, the v2-f model, and the RSM SSG model. The
particle-phase was modelled by a LPT formulation, and the particle-wall interaction was calculated
using four different models: Brauer, Grant & Tabakoff, Matsumoto & Saito and Brach & Dunn PWI
models. The 3D simulation results of mean streamwise velocities from the sixteen RANS-LPT/PWI
combinations were compared qualitatively and quantitatively to experimental and numerical
data available in the literature. The four turbulence models produced errors for the gas-phase in the
order of 8%. Concerning the particle-phase, the errors produced by all RANS-LPT/PWI combinations
were below 4% for bend angles up to 15° and up to 18% for bend angles higher than 30°. The best
results for the particle-phase were obtained with the SST k-ω and v2-f model combined with the
LPT/Brauer or LPT/Brach & Dunn PWI models, which produced errors inferior to 14%.