Reducing the drag on a circular cylinder by upstream installation of an I-type bluff body as passive control

Abstract

The bluff body cut from a small circular cylinder that is cut at both sides parallel to the y-axis was used as passive control to reduce the drag of a larger circular cylinder. The small bluff body cut is called an I-type bluff body, which interacts with a larger one downstream. I-type bluff bodies with different cutting angles of θs = 0°(circular), 10°, 20°, 30°, 45°, 53°, and 65° were located in front and at the line axis of the circular cylinder at a spacing S/ d = 1.375, where their cutting surfaces are perpendicular to the free stream velocity vector. The tandem arrangement was tested in a subsonic wind tunnel at a Reynolds number (based on the diameter d of the circular cylinder and free stream velocity) of Re = 5.3×104. The results show that installing the bluff bodies (circular or sliced) as a passive control in front of the large circular cylinder effectively reduces the drag of the large cylinder. The passive control with cutting angle θs = 65° gives the highest drag reduction on the large circular cylinder situated downstream. It gives about 0.52 times the drag of a single cylinder.