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Kali Sanjay May 1, 2006 05:52

How to calculate Velocity?
Dear Friends! Kindly help me in implementing my probem of velocity calculation in PHOENICS.

I am solving a 1-Dimensional problem consisting of soil in a cylindrical tube fitted with porous electrodes at the end. Due to electroosmotic flow, there is flow of fluid in the pores from anode to cathode. How ever this flow is a function of potential which is non uniform along the length of the tube due to change in resistance of soil with time. But the net velocity since area is same will be uniform along the length of the soil, and the pressure will change to make the velocity uniform.

So I have an equation

dc/dt + v dc/dx = D d2c/dx2

This velocity v is due to electroosmosis and hydraulic conductivity in pores, then

v=Ke*dphi/dx + Kh*dP/dx

where v=velocity

Ke=constant =Electroosmotic Permiability

Kh=constant =Hydraulic conductivity

dphi/dx = potential gradient

dP/dx = Pressure Gradient From Continuity equation


So I have an equation d(Ke*dphi/dx)/dx + d(Kh*dP/dx)/dx = 0

If I can solve this equation and find P, I can recalculate Velocity. My boundary conditions for P are atmospheric pressure at ends and I do not know the velocity at ends.

Kindly suggest me how to calculate velocity by this pressure equation in PHOENICS

Thanks in advance.

Kali Sanjay

Kali Sanjay May 1, 2006 13:57

Re: How to calculate Velocity?
In the Equation d(Ke*dphi/dx)/dx + d(Kh*dP/dx)/dx = 0 Ke, Kh and Phi as funtion of X are known, I need to find Pressure from this equation and activate conection term of solver for C. However, do I need to solve U1 and P1 in PHOENICS. If so how to implement my boundary conditions. The problem here at both ends the boundary condition for P is atmospheric pressure where as my d(Phi)/dx fuction is parabolic function.

Any help is greatly appreciated. I am struckup in implementation part in PHOENICS.

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