Numerical Research On Drag Force Characteristics Of Sands

In the paper, the drag coefficient acting on double spherical sands and flow patterns for Reynolds number Re≤300 are investigated.1. The numerical results show that the influence of the posterior sphere on the drag coefficient of the anterior one is very weak, while the influence of the anterior sphere on the drag coefficient of the posterior one is comparatively very strong. With an increase in the distance between the two spheres, such influences are becoming much weak, and the drag coefficients of double spheres are gradually approaching to that of single sphere. Besides, the drag coefficients of double spheres in tandem arrangement monotonically decrease with the increase of Reynolds number. Furthermore, the length of trailing vortex of the anterior sphere is larger than that of the single sphere, while the length of trailing vortex of the posterior one is smaller than that of the single sphere. Reynolds number at which the flow separation of the anterior sphere is caught is smaller than that at which the flow separation of the single sphere is caught; while Reynolds number at which the flow separation of the posterior sphere is caught is larger than that at which the flow separation of the single sphere is caught.2. The numerical results show that there is influence on the drag coefficient of double spherical sands placed in vertical arrangement. The influence has substantial connection with distance between the two spheres and Reynolds number. With an increase in the distance between the two spheres, the drag coefficients of double spheres are gradually approaching to that of single sphere. Because of the asymmetry of trailing vortex, the drag coefficient of double spherical sands placed in vertical arrangement will be unequal at specific distance between the two spheres and Reynolds number.3. The numerical results show that the influence on the drag coefficient of double spherical sands placed in staggered arrangement will be more serious with the reduce of angles at same Reynolds number. With the increase of Reynolds number, the drag coefficients of posterior spheres are gradually approaching to that of single sphere,at same time that of the anterior sphere is far away to that of single sphere,in the equivalent angles which are lesser than 30°。...