hi,all

i want to know that why the frequency of Drag coefficient is twice over that of lift coefficient?

i checked some books and papers, but got no answer, would you please give me a hand?

thanx in advance

kevin

If you consider a cylinder undergoing vortex shedding then the drag coefficient is the same if vortex is at its maximum height or at its minimum height wrt the cylinder. On the other hand, the lift has opposite signs for these two vortex positions. So, over one shedding period the lift cycles through once while the drag cycles through twice.

thanx a lot, Bob.

i knew this that "the drag coefficient is the same if vortex is at its maximum height or at its minimum height wrt the cylinder. On the other hand, the lift has opposite signs for these two vortex positions", but if f_Cd is 2^n*f_Cl, the phenomenon you said also seems reasionable, then, maybe Cd arrives its mininum as vortex at the mean height(on the axis of the cylinder)?

# Cd is coefficient of drag and Cl of lift.

please give me more details.

It is the same thing as compare sin(t) with (sin(t))^2.

The square of the sine oscillates twice as fast as the pure sine.

Cheers