# Reg - Log result

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 November 25, 2010, 05:25 Reg - Log result #1 New Member   Hari Krishnan Join Date: Mar 2009 Location: chennai, Tamil nadu, india Posts: 27 Rep Power: 6 Dear All, I am into a calculation of to find out the air volumetric flow rate of a flow path. To intialize the flow conditions,under simpleFoam, I have followed up these below mentioned relaxation factors. iteration time 0-300 p - 1e-5, 0.001, 0.8 U - 1e-5, 0 , 0.01 epsilon - 1e-3, 0, 0.01 k - 1e-3, 0, 0.01 R,nutilda - 1e-3,0, 0.01 Inlet presssure, 7000pa, and outlet is 0 pa. In the 0th time, the k was intialized as 0.0001 and epsilon with 0.01. By replacing the 300th time to 0th time, iterated to time-4000 with following relaxation factors p - 1e-6, 0.0001, 0.3 U - 1e-5, 0.001 , 0.4 epsilon - 1e-4, 0.01, 0.4 k - 1e-4, 0.01, 0.4 R,nutilda - 1e-4,0.01, 0.4 But the calulation log result shows the continutiy errors in a abnormal high values Time = 1 DILUPBiCG: Solving for Ux, Initial residual = 0.0407914, Final residual = 5.31414e-06, No Iterations 3 DILUPBiCG: Solving for Uy, Initial residual = 0.125808, Final residual = 1.32436e-05, No Iterations 3 DILUPBiCG: Solving for Uz, Initial residual = 0.0630549, Final residual = 6.17269e-06, No Iterations 3 GAMG: Solving for p, Initial residual = 0.579967, Final residual = 3.21338e-05, No Iterations 7 time step continuity errors : sum local = 0.182605, global = -0.00299876, cumulative = -0.00299876 DILUPBiCG: Solving for epsilon, Initial residual = 0.165768, Final residual = 0.00011708, No Iterations 2 DILUPBiCG: Solving for k, Initial residual = 0.163874, Final residual = 0.000211085, No Iterations 2 ExecutionTime = 4.44 s ClockTime = 5 s ; ; Time = 100 DILUPBiCG: Solving for Ux, Initial residual = 0.00241212, Final residual = 4.29667e-06, No Iterations 2 DILUPBiCG: Solving for Uy, Initial residual = 0.00441536, Final residual = 8.43683e-06, No Iterations 2 DILUPBiCG: Solving for Uz, Initial residual = 0.00218416, Final residual = 5.32736e-06, No Iterations 2 GAMG: Solving for p, Initial residual = 0.0230018, Final residual = 1.37452e-06, No Iterations 11 time step continuity errors : sum local = 0.00326717, global = -0.000564809, cumulative = -0.125284 DILUPBiCG: Solving for epsilon, Initial residual = 0.00320255, Final residual = 2.24605e-06, No Iterations 2 DILUPBiCG: Solving for k, Initial residual = 0.00374825, Final residual = 4.17044e-06, No Iterations 2 ExecutionTime = 269.62 s ClockTime = 297 s ; ; Time = 300 DILUPBiCG: Solving for Ux, Initial residual = 0.00123843, Final residual = 2.41581e-06, No Iterations 2 DILUPBiCG: Solving for Uy, Initial residual = 0.00156465, Final residual = 4.65099e-06, No Iterations 2 DILUPBiCG: Solving for Uz, Initial residual = 0.000839765, Final residual = 3.14799e-06, No Iterations 2 GAMG: Solving for p, Initial residual = 0.00826977, Final residual = 6.9471e-07, No Iterations 9 time step continuity errors : sum local = 0.00204741, global = 0.000325488, cumulative = -0.0805461 DILUPBiCG: Solving for epsilon, Initial residual = 0.00197012, Final residual = 1.65425e-06, No Iterations 2 DILUPBiCG: Solving for k, Initial residual = 0.00200665, Final residual = 2.1513e-06, No Iterations 2 ExecutionTime = 762.05 s ClockTime = 858 s ; ; Time = 500 DILUPBiCG: Solving for Ux, Initial residual = 0.155768, Final residual = 1.1042e-06, No Iterations 4 DILUPBiCG: Solving for Uy, Initial residual = 0.215307, Final residual = 6.0912e-05, No Iterations 3 DILUPBiCG: Solving for Uz, Initial residual = 0.189597, Final residual = 1.63893e-05, No Iterations 3 GAMG: Solving for p, Initial residual = 0.521073, Final residual = 3.20929e-05, No Iterations 14 time step continuity errors : sum local = 217.793, global = 40.7283, cumulative = 50.0885 DILUPBiCG: Solving for epsilon, Initial residual = 0.0943214, Final residual = 0.000226612, No Iterations 1 DILUPBiCG: Solving for k, Initial residual = 0.0949947, Final residual = 4.71994e-05, No Iterations 2 ExecutionTime = 1336.27 s ClockTime = 1545 s ; ; Time = 775 DILUPBiCG: Solving for Ux, Initial residual = 0.313058, Final residual = 7.33734e-05, No Iterations 3 DILUPBiCG: Solving for Uy, Initial residual = 0.362856, Final residual = 7.80359e-05, No Iterations 3 DILUPBiCG: Solving for Uz, Initial residual = 0.271597, Final residual = 3.44234e-05, No Iterations 3 GAMG: Solving for p, Initial residual = 0.493461, Final residual = 4.4403e-05, No Iterations 16 time step continuity errors : sum local = 2.07578e+11, global = -5.99968e+10, cumulative = -4.56283e+10 DILUPBiCG: Solving for epsilon, Initial residual = 0.565744, Final residual = 0.00559245, No Iterations 1 DILUPBiCG: Solving for k, Initial residual = 0.337978, Final residual = 0.00124628, No Iterations 1 ExecutionTime = 2159.84 s ClockTime = 2584 s The fvscheme was : ddtSchemes { default steadyState; } gradSchemes { default Gauss linear; grad(p) Gauss linear; grad(U) Gauss linear; } divSchemes { default none; div(phi,U) Gauss upwind; div(phi,k) Gauss upwind; div(phi,epsilon) Gauss upwind; div(phi,R) Gauss upwind; div(R) Gauss linear; div(phi,nuTilda) Gauss upwind; div((nuEff*dev(grad(U).T()))) Gauss linear; } laplacianSchemes { default none; laplacian(nuEff,U) Gauss linear corrected; laplacian((1|A(U)),p) Gauss linear corrected; laplacian(DkEff,k) Gauss linear corrected; laplacian(DepsilonEff,epsilon) Gauss linear limited 0.5; laplacian(DREff,R) Gauss linear corrected; laplacian(DnuTildaEff,nuTilda) Gauss linear corrected; } interpolationSchemes { default linear; interpolate(U) linear; } snGradSchemes { default corrected; } fluxRequired { default no; p; } I had tried by giving the relaxation factors 0.1,0.2,0.2.. for p,u,epsilon.. resp. Kindly advise me what would the time step continutiy errors high value indicates and how to identify where i would mistake? Kindly suggest me a solution Thank you, Hari

 November 25, 2010, 07:18 Reg - Time step continuity error #2 New Member   Hari Krishnan Join Date: Mar 2009 Location: chennai, Tamil nadu, india Posts: 27 Rep Power: 6 I am trying to recognize the issue with related to the past threads. There were previous solutions like changing the fvschemes,fvsolutions, even downscaling etc.. I wont feel those are appropriate to my issue. When I see the 100,200,300 time iterations in paraview, the flow got stabilised within this 300 time iteration itself when another type of relaxation factors were given. Any suggestion would be appreciable and helpful for me. Thank you, Hari

 February 15, 2011, 06:32 #3 New Member   Hari Krishnan Join Date: Mar 2009 Location: chennai, Tamil nadu, india Posts: 27 Rep Power: 6 May I know whether the above mentioned details are not enough for avail solution? I dont know why is not there a single reply for this topic. Anyone suggest me. Thank you, Hari

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