Interaction between fixed dual particles at moderate Reynolds numbers

Numerical simulations of 3D flow past two identical spheres which are held fixed relative to each other at different separation distances and angles (which describe the deviation from the centre line of the trailing particle) are carried out. Particle Re = 300 is used to investigate the dependency of drag and lift coefficients on the separation distances and the angles. The simulations are performed on a Cartesian grid using the Volume of Solid (VOS) method to represent the spherical particles. Comparison with experimental and numerical data shows that method can accurately resolve the flow field around the spheres and the forces they are subjected to. Results are focused on the behaviour of forces (drag and lift) affected by the presence of another particle. The drag of the reference and secondary sphere is greatly affected when they are placed in tandem arrangement at a gap of 2.5 - 3d and 1.5d respectively. Similarly the lift of the reference sphere is greatly affected in the arrangement when the spheres are placed in the symmetry plane at gap of 1.5d and angle of 45 degrees. The effect of both forces decrease as the gap is increased in all arrangements. The flow becomes unsteady and periodic at a separation distance of 3d for the tandem case. Irregular vortex shedding is observed at large separation distances 6 - 9d. The results for forces coefficients and the vortex shedding show great resemblance for the cases when the spheres are placed in symmetry plane and plane perpendicular to it at same gaps and angles. The characteristics of the flow, wake and the vortical structures are investigated in detail in the present study