Tham khảo tài liệu 'particle-laden flow - ercoftac series phần 5', ngoại ngữ, anh ngữ phổ thông phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | DNS of particle-laden flow over a backward facing step at a moderate Reynolds number A. Kubik and L. Kleiser Institute of Fluid Dynamics ETH Zurich Switzerland kubik@ Summary. The present study investigates turbulence modification by particles in a backward-facing step flow with fully developed channel flow at the inlet. This flow configuration provides a range of flow regimes such as wall turbulence free shear layer and separation in which to compare turbulence modification. Fluid-phase velocities in the presence of different mass loadings of particles with a Stokes number of St are studied. Local enhancement and attenuation of the streamwise component of the fluid turbulence of up to 27 is observed in the channel extension region for a mass loading of Ộ . The amount of modification decreases with decreasing mass loading. No modification of the turbulence is found in the separated shear layer or in the re-development region behind the re-attachment although there were significant particle loadings in these regions. 1 Background The use of Direct Numerical Simulations DNS to predict particle-laden flows is appealing as it promises to provide accurate results and a detailed insight into flow and particle characteristics that are not always or not easily accessible to experimental investigations. In the present study a vertical turbulent flow over a backward-facing step with gravity pointing in the mean flow direction at moderate Reynolds number ReT 210 based on friction velocity uT and inflow channel half-width h is investigated by means of DNS. The main focus is directed towards particle statistics and turbulence modification. Fessler and Eaton 9 reported the results of experiments on particle-laden flows in a backward-facing step configuration. Like in our simulations in this work the bulk flow rate was fixed. The corresponding Reynolds number was approximately ReT 644. The experiments were performed with glass and copper particles of .
