Damping Constant

[scotland6]

Hi,

Can someone help me work out the damping constant of a cylindrical viscous damper. I know the viscosity of the oil, the ID of the tube, the OD of the piston and its velocity. The oil is effectivly being forces through an annular area from one side of the piston to the next.
Any help appreciated.

Scotland6

 

[ivymike]

you can probably find how to calculate the force vs. velocity for the piston by looking in a fluids textbook.

using F = -cv, you can relate your coefficient c to the F and v that you calculate or measure.

 

[btrueblood]

The problem is a variant of Couette flow.

 

[scotland6]

Hi,

Sorry didn't know the piston velocity initially but determined it by testing. Can c be calculated without knowing velocity at this stage?

Scotland6

 

[ivymike]

if your velocity is within a range, you can calculate c based on the relationship of F to v. I'd think the big concern is whether your Reynolds number stays in the same neighborhood or not (but it's been a long time, and I don't have a fluids text handy).