Numerical simulation of two-phase flow in screw-conveyor sedimentation centrifuge

The paper simulates the aerodynamics of a two-phase flow in the cylindrical part of the screw auger precipitation centrifuge in order to estimate the centrifugal forces in the central region of the centrifuge, due to problems of sedimentation of the solid fraction from the suspension. According to the obtained velocity field, the time and the trajectory of the deposition of solid particles of different diameters of a two-phase flow of different diameters are calculated. This is necessary to estimate the speed of rotation and the pitch of the screw for outputting solid sediment to the discharge windows. The resulting model will optimize the existing apparatus for centrifuging two-phase flows, as well as help in the design of new plants

Analysis of Flow Field behind a Road Vehicle With/Without Rear Air Spoiler

A particle image velocimetry (PIV) technique has been used to analyze the flow characteristics behind a road vehicle with/without an air spoiler attached on the behind end and also to estimate its effect on the wake. A vehicle model scaled in the ratio of 1/18 is set up in the mid-section of a closed-loop wind tunnel. The Reynolds number based on the vehicle length is taken in the range of 16.37x103 up to 3.77x105, i.e. (V = (2 to23.7 m/s). Measurements are carried out on the planes parallel to the free stream to investigate the two-dimensional structure of the flow field patterns on the vortices zone. There are significantly different vorticity distributions in the recirculation region; this depends upon the existence and height of the air spoiler. In general, the positions of the vortices are far away from the vehicle rear end due to the usage of the air spoiler. In addition, the levels of turbulence intensity and kinetic energy increases as the vehicle speed increases. The wing tip vortices generate the down force and as a result, they might make the vehicle more stable in driving