Drag on a Cylinder with an Apple Shaped Cross Section
The drag on a cylinder with an apple shaped cross section was studied numerically in this paper. This cross section is adopted because the drag on an apple is known to be lower than that of a sphere. Since the hollows of an apple seem to be points of drag reduction, two dimensional numerical simulations of cylinders with hollows of several shapes are carried out at a Reynolds number of 6.7 x 104 by using the vortex method to check their effects. The cylinder with hollows like those of a real apple attained a 13% reduction in drag compared with a circular cylinder. Other geometrical hollow shapes, namely, V shaped and U shaped grooves, also reduced drag from the circular model, but these effects were less pronounced than those of the apple shaped cross section. It was concluded that an apple like hollows were effective for drag reduction of a cylin der as well as a sphere.