|November 6, 2006, 07:10||
Velocity in Porous medium : HELP! HELP! HELP!
I have a query regarding solving of velocity in a porous domain. I have a sort of tube which is filled with soil in a section which causes the area to decrease. The tube is left to open at both ends. I am solving for a velocity profile and the source of velocity is due to electroosmosis in the soil which is a function of x(sort of pumps in series of different capacities ).
So soil acts like a pump. I am solving for 1-D Cartesian coordinates and I can write the velocity as
Actually the part Ke*dV/dx is source of velocity which I can calculate. The second part of the above equation will be calculated for satisfying continuity equation. As the velocity is different , the pressure actually will compensate for making it uniform. I hope I can solve this problem using PHOENICS.
I gave the porosity as
Where my region 2 is packed with soil.
I calculated Ke*dv/dx at every point in the soil and specified as velocity source in ground.
In GROUP 13 for GRND (Value), I specified Ke* dv/dx........v is potential (volts)
I specified pressure boundary conditions as P=0 at ends with initial Pressure P specified as Zero at all points.
These are my inital and boundary conditions for U1 and P1
PATCH(ANODE,WEST,1,1,1,1,1,1,1,LSTEP) COVAL(ANODE,P1,FIXP,0.0) COVAL(ANODE,U1,ONLYMS,0.0)
PATCH(CATHODE,EAST,NX,NX,1,1,1,1,1,LSTEP) COVAL(CATHODE,P1,FIXP,0.0) COVAL(CATHODE,U1,ONLYMS,0.0)
Is it the correct way? I have found that when CONPOR is specified as CELL, the AEAST shows the same area as non-porous region and I think the volume decreases, but area remains same (Internally propably PHOENICS takes volume as DXU2D *AEAST*Porosity). In that case the velocity that I need to specify should be superficial velocity. What I know Ke * dv/dx is actual velocity in pore. Do I need to multiply this velocity with porosity and give as area patch for velocity?
I am not sure whether I had pose my problem correctly or not, in summary, 1. Is CONPOR fixing the way I did is OK? 2. Can I specify known velocity field in the cells and set PHOENICS to solve for pressure to satisfy the continuity equation and get uniform velocity? I just know pressure at ends (atmosphere) and velocity source Ke*dv/dx in soil. 3. Do I need to activate DARCY=T and fix DARCON for #2 region?
Please please help me. I am really struck up.
Thank you in advance,
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