What Is A Stability Parameter (in Reference To Fluid Mechanics)?
Posted by admin on November 26, 2009 under Fluid Mechanics | 
2 Comments to Read
I am working on a problem with a fluid between two parallel plates, one moving and one stationary. For each liquid and “time step”, there is a different stability parameter. Could you please explain what this is?
stevey22 said,
Generally, to move a body through a fluid or a fluid through a canal, you need a force to overcome the friction.
If the velocity is slowly enough, the resistance force tends to go to zero.
Imagine the fluid between your two plates to be homogene, of constant temperature and a newtonian fluid.
The lower plate is stationary the upper plate moves with the velocity w
The profile of the velocity increases linear from w=0 (at y=0) to w (at y=y)
The tangential force that causes the motion of the upper plate is proportional to the velocity reciproce proportional to the distance y:
F~w/y
The fluid particles in the different levels have differents velocities which causes a shear stress (tau):
F=(tau)*A=(eta)*A*w/y
with
A=area of the plates
(eta)=proportional factor=dynamic viscosity
w/y:=D
with
D=velocity gradient
->(tau)=(eta)*D
The dynamic viscosity is a characteristic quantity of the fluid and depends on the pressure and the temperature.
Xenophon said,
This refers to the stability of the boundary layer.
The fluid is split into two parts:http://en.wikipedia.org/wiki/Boundary_la…
I’m not sure which parameter(s) this means
Falkner-Skan? Grashof?
Here is some material to look at with graphs:http://euroturbo.org/research/themes/aer…
Sorry I can’t help more…I’m still learning this stuff myself.
Add A Comment