Experimental Investigation On Flow Around A Cylinder Group

Flow around a circular cylinder exists in a lot of engineering practice. Karman Vortex Street will be produced when the fluids flow around the cylindrical structures. The periodic lift force and drag force that the structures suffered may caused resonance and destroy the structures. Flow around a cylinder group was investigated experimentally and numerically in this study. The investigation was mainly focused on the flow patterns behind the cylinder group and the hydrodynamic parameters of the cylinder group.The cylinder group was consisted of19identical cylinders in this study. Five different diameter ratios was tested. The distribution of longitudinal time-averaged velocity and turbulence intensity was measured, and the frequency of the separating shear layers was calculated. Flow visualization methods were used to visualize the surface flow field and the gap flow. The numerical model was built as the experiment. The vorticity distribution of the wake was calculated, as well as the lift coefficient and drag coefficient of each cylinders of the group. The results show that the shear layers behind the cylinder groups with small diameters ratios separated with fixed frequency, the flow pattern was similar to that of a single cylinder. No fixed frequency was found in the wake behind the cylinder groups with large diameter ratios. However, the lift force and drag force changed with a fixed frequency. For the cylinder groups with large diameter ratios, The velocity recovered more slowly, and entrainment effect to the surrounding fluid was weaker for the cases with large diameter ratios.Finally, flow around a cylinder group with different Reynolds numbers was investigated numerically. The vorticity distribution of the wake was calculated, the curves of hydrodynamic parameters over velocity of coming flow were presented.