# Velocity in Porous medium : HELP! HELP! HELP!

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 November 6, 2006, 07:10 Velocity in Porous medium : HELP! HELP! HELP! #1 Kali Sanjay Guest   Posts: n/a Sponsored Links Dear Friends! 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 ). --Non-porous--|---Soil-Porous---|--Non-porous-- So soil acts like a pump. I am solving for 1-D Cartesian coordinates and I can write the velocity as d((Ke*dV/dx)+(Kh*dp/dx)/dx=0 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 CONPOR(CAREA,PRST,CELL,#2,#2,1,1,1,1) 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. PATCH(VSPD,CELL,1,NX,1,1,1,1,1,LSTEP) COVAL(VSPD,U1,FIXVAL,GRND) 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 FIINIT(U1)=1E-10 FIINIT(P1)=0 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, Regards, Sanjay

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