Abstract
Two circular cylinders in tandem arrangement were pulled in a tank filled with glycerin.
Both of CDf and CDr become smaller with decreasing the gap of two cylinders, where CDf and CDr imply the drag coefficient of the upstream cylinder and that of the downstream one, respectively.
In the case of two equal cylinders, the value of CDf/CD and CDr/CD are about 0.6?0.7 and 0.5?0.6, respectively, at ε/a=0.2 and in the range of 3×10-2<R<1.5×10-1, where CD is the drag coefficient of a single cylinder in a uniform flow, ε the gap of two cylinders, a the cylinder radius and R the Reynolds number.
In the case of two different cylinders in the radius ratio 3:1, both of CDf and CDr of a small cylinder are always smaller than that of the case of two equal cylinders at equal Reynolds numbers. There exists separation bubbles in flow fields between two cylinders at ε/as <5, where as is the radius of the small cylinder.
