Large Eddy Simulation Of Flow Around One And Two Circular Cylinders

Circular cylinder and cylinders are widely used in engineering field. The phenomenon of flow around structures can be seen in our daily life. The eddies will be sheded when flow pass structures that are not streamline, and the periodically changing forces caused by the shedding eddied will make the structures vibrated, or even destroyed. For a group of circular cylinders, the pressure on cylinders will be different with it on a single cylinder because of the interation between cylinders near by. In hydrodynamics, flow around cylinders has been one of the significant problems in foundamental research and engineering field.Based on the LES method of FLUENT, flow around one and two circular cylinders arranged differently was carried out, the instantaneous and time averaged flow field and the force on circular cylinders ware analyzed.For the single cylinder, when the Reynolds number equals to 3900, the pressure coefficient on the cylinder is equal to 1.0 in front of the cylinder, reduces to minimum along with the extention to the round of the cylinder, then increases to a steady value rapidely, and the pressure distributes steady behind the cylinder. The separate angle is equal to 72°, which is approach to the experimental data. The frequency of the drag force coefficient is twice of the lift force coefficient, and the Strouhal number is equal to 0.216. There is a recirculation region which is about 1D long behind the cylinder.When the Reynolds number equals to 6×104, for the two circular cylinders arranged tandem, the pressure on cylinder downstream is obviously smaller than the cylinder upstream, its frequency of the drag force coefficient is twice of the lift force coefficient, and their frequencies of eddy shedding are approximately the same, and their phases of the vortex street are the same; for the two circular cylinders arranged side by side, their drag force coefficients are approximately the same, and their frequencies of eddy shedding are approach to the single cylinder, and their vortex street have opposite phases; for the two circular cylinders arranged staggered 45°, they have the same frequency of eddy shedding, and the vortex street phase of the cylinder downstream is later than the cylinder upstream obviously.