the difference between system equili and system and steady state

[hi]

Can anyone explain the difference between a system at equilibrium and a system at steady-state water flow?

I know that equilibrium occurs at equal rates, no net change is produced. But I don't understand steady state system....Please explain it to me.... Thanks


also the difference between saturated and unsaturated hydraulic conductivity? I have hard time to understand these stuffs.. If anyone know these stuffs, can u please explain it to me. Thanks.

[Tom Mattson]

I'm moving this to Physics, where perhaps it will get some discussion.

[Alexander]

Equilibrium: dU/dx = 0 (usually this happens at extrema of potential energy).

[Tom Mattson]

Originally posted by hi
I know that equilibrium occurs at equal rates, no net change is produced.


OK, at first I thought you meant the "zero force" condition, but now I am thinking that you are referring to the continuity equation. That is because when you say "equal rates", it makes me think of "equal flow rates into and out of a volume".

So, that statement of equilibrium would be:

[nab].j+∂ρ/∂t=0


But I don't understand steady state system....Please explain it to me.... Thanks


I dug up the old Fluid Mechanics book (it's been about 10 years!) and looked up the mathematical definition of steady state. It is...

∂A/∂t=0

for any fluid property A. That would include the density ρ, which reduces the continuity equation to:

[nab].j=0


also the difference between saturated and unsaturated hydraulic conductivity? I have hard time to understand these stuffs.. If anyone know these stuffs, can u please explain it to me. Thanks.

This I don't know. Our local "fluids" guy is Enigma; try sending him a PM.

edit: fixed ∂ signs.

[Alexander]

I would call steady state a state at which power (rate of chande of energy dU/dt) is constant.