Abstract
An experimental study on the effect of cut angle on circular cylinders to the drag force is performed. Six cylinders were cut at different angles and the air flow impinges perpendicular to the cut surface of the cylinder. The cut angles applied include: 0°, 30°, 45°, 53°, 55°, and 75°. The shear layer visualisation on the surface of cylinder was conducted as well. Drag force was measured using a wind tunnel force balance and the wind speed was set so that a corresponding Rey-nolds number of 5.3 × 104 was achieved. Visualisation was carried out by covering the cylinder with paper wetted by mixture of oil and titanium dioxide powder. Experimental results show that drag force has similar trend to that of previous experiment results. The minimum drag coefficient is attained at the cut angle of 53°. From oil streak visualisation the streamlines pattern of the flow over the cylinder could be reconstructed.
Highlights
All objects submerged in a fluid flow experience aerodynamics forces due to the interaction between the objects and the flow
Visualization was carried out by covering the cylinder with paper wetted by mixture of oil and titanium dioxide powder.The experimental results show that the drag force has similar trend to that of previous experiment results
The streamline patterns of the flow past the cylinder could be reconstructed by judging the oil streak visualization
Summary
All objects submerged in a fluid flow experience aerodynamics forces due to the interaction between the objects and the flow. Reduction of the existing forces act on an object can be done by controlling the boundary layer development on the object surface. The reduction in drag by cutting the surface perpendicular to the incoming flow works for a sphere placed in the fluid flow [3,4,5]. If the flow is not perpendicular to the cutting surface of the sphere, the flow will generate lift and change drag forces on the object [5]. There are many other objects having circular cylinder shape submerged in fluid flow. These include electricity poles, bridge piles, industrial chimneys, tubes in heat exchangers, and supporting column for offshore constructions.
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