Why my script cannot run properly?

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Author Message   jzh New member Username: jzh Post Number: 1 Registered: 07-2010 Posted on Tuesday, August 17, 2010 - 05:48 am:    I have a set of time-dependent PDEs with 4 unknown variables, the sentences are OK but FlexPDE cannot run it properly, i don't know how to adjust it. My script is below: title "Axisymmetric (Y Cylinder) Biot Consolidation" coordinates ycylinder('R','Z') variables Ur(0.01),Uz(0.01),Wr(0.01),Wz(0.01) definitions B1 = 2 B2 = 0 B3 = 0 B4 = 2.001 B5 = 1 B6 = -1 B7 = -1 B8 = 0 ep = dr(Wr) + Wr/r + dz(Wz) Sr = (2*B1+B2) * dr(Ur) + B2 * (Ur/r) + B3 * dz(Uz) - B6 * ep St = B2 * dr(Ur) + (2*B1+B2) * (Ur/r) + B3 * Dz(Uz) - B6 * ep Sz = B3 * dr(Ur) + B3 * dz(Uz) + B4 * dz(Uz) - B7 * ep Tzr = B5 * ( dz(Ur) + dr(Uz) ) Sf = B6 * dr(Ur) + B6 * (Ur/r) + B7 * dz(Uz) -B8 * ep initial values Ur=0 Uz=0 Wr=0 Wz=0 equations Ur: dr(r*Sr)/r - St/r + dz(Tzr) = 0 Uz: dr(r*Tzr)/r + dz(Sz) = 0 Wr: dt(Wr) = -dr(Sf) Wz: dt(wz) = -dz(Sf) boundaries region 1 start(0,0) load(Uz) = -1 line to (1,0) load(Uz) = 0 line to (50,0) value(Uz) = 0 value(Ur) = 0 line to (50,20) value(Uz) = 0 value(Ur) = 0 value(Wz) = 0 value(Wr) = 0 line to (0,20) load(Uz) = 0 load(Ur) = 0 load(Wz) = 0 load(Wr) = 0 line to close time 0 to 0.1 plots for t =0 by 0.01 to 0.1 contour(Uz) as "Z-Displacement" end   jzh New member Username: jzh Post Number: 2 Registered: 07-2010 Posted on Tuesday, August 17, 2010 - 05:49 am:    Hope someone can help me! Thanks!   jzh Junior Member Username: jzh Post Number: 3 Registered: 07-2010 Posted on Thursday, August 19, 2010 - 02:44 am:    I'm looking forward to the answer! Anyone can help me? Thanks!   mgnelson Moderator Username: mgnelson Post Number: 205 Registered: 07-2007 Posted on Thursday, August 19, 2010 - 11:18 pm:    There appears to be an instability in your equations somewhere, and the solution is going crazy near the point (0,1). When I zoom in, you can see that one cell starts to get increasingly large values, escalating higher and higher. I would suggest plotting all your variables and any important definitions to try and discover which part of your equation is responsible. You could also try starting with just the stress portion of your system and make sure that works first before going to the complete consolidation problem. script1.pde (1.2 k)   jzh Member Username: jzh Post Number: 4 Registered: 07-2010 Posted on Friday, August 20, 2010 - 09:16 pm:    Thank you for your suggestion. I have tried the stress portion and found it ok, at least no apparent error, though i don't know the accurate solution. I will try to find some incorrectness in my original system. Below is my results for only stress: BiotStress01.png (7.5 k) BiotStress02.png (12.7 k)   jzh Member Username: jzh Post Number: 5 Registered: 07-2010 Posted on Friday, August 20, 2010 - 09:18 pm:    And I want to know what code I can use to make my picture shown in my post, not as a link!   jzh Member Username: jzh Post Number: 6 Registered: 07-2010 Posted on Friday, August 20, 2010 - 09:30 pm:    How can .png be pasted in the post?   mgnelson Moderator Username: mgnelson Post Number: 206 Registered: 07-2007 Posted on Friday, August 20, 2010 - 11:57 pm:    I am not sure why your PNG files are shown as links... My PNG file displayed as a graphic. Uploading an attachment should display the graphic whether it is PNG, JPEG or GIF.