The Flow of a Surfactant Solution around a Circular Cylinder (Onset of Drag Reduction)

Effects of a drag reducing surfactant solution on the flow around a circular cylinder were investigated in a Reynolds number range 200<Re<5000. In this experiment, the drag coefficient on a circular cylinder in surfactant solution was measured by the means of a load cell. In addition, we conducted the flow visualization experiments. For lower Reynolds number, the data of drag coefficient showed higher values for the surfactant solution than those for water. In the case of the cylinder diameter of 20mm, drag reduction occurred when the Reynolds number reached about 3000. It was seen that the drag of a circular cylinder in surfactant solution increased with Reynolds number in Re<3000 for d=20mm by the existence of the low velocity zone around the cylinder.