air flow past a flat plate at some inclined angle

[CondensedMatter]

I need to do a calc that involves an inclined plate at some arbitrary angle with fluid flow around it. More specifically, the plate pivots about an axis, and I'm looking to express the reaction moment (for steady state conditions) about its pivot axis as a function of inclined angle, fluid velocity, surface area, area centroid moment arm, etc.

One simple approach is to go the Bernoulli route, and assume stagnation occurs at the exposed surface area, but clearly this conservative estimation has its limitations.

Incompressible flow can be assumed. 2D model probably could be sufficient.

 

[40818]

Have a look at the theory behind aeroelasticity, this will point you in the right direction.

 

[rb1957]

flow over a flat plate should be simple aerodynamics ... consult an aero. text book ...

on this topic, I thought Newton was wrong ...

or is it that he's ok for a flat plate, but wrong for a wing ?

if your hinge is anywhere off the midpoint of your plate (and you don't support the plate (as statics that over), I think you're in for a dull experiment. if you support the plate, or if you hinge the plate at the middle, it might be interesting to see the sensivity ... if the flow is EXACTLY aligned to the plate nothing will happen; if it is SLIGHTLY off that the plate will probably depart (lift overcomes weight), stall, depart the opposite side ... this is heading towards the aeroelastic (flutter) suggestion above

 

[Feric]

Hi there:

Just to be on the safe side, check the Mach number.

If it is a low value, then it is incompressible flow and the Bernoulli equation should do it for you. Otherwise, it is compressible flow.

Thanks,

G. Feric, PE

http://engware.i-dentity.com

 

[cpsenior]

If the angle of attack is not that steep and you can assume the flow stays attached, you can use thin airfoil theory to calculate CL,CD, and CM. But be careful since the higher the incidence angle gets, the error gets higher using this estimation.

 

[saksmito]

I agree with cpsenior.
For high angles (this has just passed through my mind now) in first I would suppose a detached current around the edges. Study it assuming the current impacts the plate, the flow runs through the plate and then goes straight ahead following the original current path. For the pressure loss I would assume the same as for a "calibrated orifice" (literal translation from spanish, don´t know if it´s correct in english) with the remaining current surface (assuming it´s into a pipe)

Of course it all depends on the accuracy you are searching.

 

[sjbjcl]

This web site might help.

http://www.grc.nasa.gov/

http://WWW/K-12/airplane/falling.html

 

[fredt]

This sounds like a damper blade application. One thing to note is that the centre of pressure isn't necessarily at the centre of the plate depending on the angle of attack.

It is difficult to find airfoil data when the damper is near closed and empirically torque is greatest at around 80 deg to the duct axis. The cascade effect will also come into play in multiple bladed cases.