What is the formula for calculating drag on spherical objects in laminar flow?

[jadex]

Hi

I'm looking for a place were I can find the damping coefficient for water. Maybe someone has/can find/knows a good site/table/url?

thank you

 

[jadex]

I thinks the correct english term is "drag".
this link show what I'm looking for
http://en.wikipedia.org/wiki/Drag_(physics)
I need values of the 'b' for water in the equation F=-b*v
Anyone?

 

[jacobsmith]

Sorry to bump an old topic, but I am interested in the same thing. I know the damping coefficient of blood is .7, so I would think that water is around .2 or .3. Does anybody know for sure?

 

[jasc15]

The damping coefficient is not a constant for a particular fluid. Velocity is not the only variable to which drag force depends, but you can reduce the other factors to a constant by determining the Reynolds number (which itself is a function of viscosity, geometry of the object moving through the fluid, etc.) and a number of other factors. It can also be experimentally determined by actually moving the object through the fluid at different speeds and observing the relationship between speed and drag.

 

[jacobsmith]

You're right, I should have done more research before asking. The problem is actually a bit more complex than I thought.

It can also be experimentally determined by actually moving the object through the fluid at different speeds and observing the relationship between speed and drag.

Not exactly the easiest thing in the world, since the object in question is a red blood cell. :P

Thanks a lot for answering.

 

[nasu]

For spherical objects and laminar flow the drag can be calculated from Stokes' formula:
drag=6*PI*n*R
where n is the viscosity of the fluid and R is the radius of the sphere.
It works for Reynolds numbers less than 1, I think.