graph does not show values

[chikhlas]

whenever i try to plot graphs for steady coupled fluid flow and thermal and follows the steps to show values in graphs, nothing appears, only path plots aare available but i wish to plot load vs time. my experiment values are very small in e-5

but graphs appears in m/s, etc. i'm usig 2010 version

[chikhlas]

sorry 2012 version

[Joey.X]

Could you post your model(if small) or screen shot? Thanks.

[chikhlas]

i did it last night, now its ok but can you explain me a bit about path plot, path plot appears load vs distance? what is the theory behind path plot, how can i describe plots? what is the meaning of distance here? distance between each node? it varies if we plot in total or any specific direction axis, the its value is too much in meters, altough complete model dimensions are appprox 0.092m x 0.040m.

kindly give me basic theory behind path plot so i could explain it in my report. i attached one of these.

thanks

[Joey.X]

Path plot is one of the post-processor functions, which shows the available result (y axis) vs. distance(x Axis). No particular theory behind it, but one may need to know that the plot connection is by node id number from selected nodes, i. e, sorted by node ID.

The meaning of distance (default) is the space distance (3D) from node i to node i+1. But user has options to change to the component distance x,y or z.

The total distance in x axis is the total travel distance from your selected node 1 to node N, so it is normal that this is larger than the dimension size of your simulation domain if you pick many nodes.

[chikhlas]

sorry to bother you again, can you give me an understanding about temperature, why my model shows a temperature of zero degree on some surfaces and nodes. although applied temperature is 50degree and surrounding temperature is 20 degree. it must show minimum value of 20 degree for those part where temperature value of 50 degree is not applied. However if it shows zero degree then how can i explain this thing to others and in my project report.

[Joey.X]

hi, Chikhlas,

I did have a look of your attached screen shot. It looks to me that the result pattern appears not converged, which may came from multiple reasons; could you provide more information such as all loading setup and log file (.lgs or .lgt files)? Does it have multiple parts in this model? if yes, what were the contact setups between part surfaces? Thanks.

[chikhlas]

kindly see attached file

Autodesk (R) Simulation Steady-State Heat Transfer Version 2012.01.00.0017-W64/X64 15-Jun-2011 Copyright (c) 2011, Autodesk, Inc. All rights reserved. DATE: AUGUST 29, 2011 TIME: 02:10 PM Input Model: C:\Users\Ikhlas\Documents\autocad\789.ds_data\8\ds PROGRAM VERSION: 201201000017 ALG.DLL VERSION: 201201000017 AlgConfig.DLL VERSION: 201201000017 Agsdb_AR.DLL VERSION: 201201000017 AMGSolve.DLL VERSION: 201201000017 AlgSolve.DLL VERSION: 201201000017 **** Model Unit System Settings: -------------------------------------------- Unit System : Custom Force : N Length : mm Time : s Temperature (Absolute) : deg C (K) Thermal Energy : J Voltage : V Current : A Electrical Resistance : ohm Mass : N*s^2/mm -------------------------------------------- Thermal **** CONTROL INFORMATION number of node points = 277691 number of element types = 9 analysis type code = 10 equations per block = 0 bandwidth minimization flag = 0 **** PHYSICAL CONSTANTS USED WHEN APPLICABLE The Stefan-Boltzmann Constant = 5.668E-14 Temperature Increment to Absolute = 2.731E+02 **** NON-LINEAR ITERATION CONTROL PARAMETERS Nonlinear control option = ON Convergence criterion = 2 Maximum number of iterations = 15 Interval for monitoring = 5 Corrective tolerance = 1.0000E-03 Relative tolerance = 1.0000E-03 Relaxation parameter = 1.0000E+00 **** PRINT OF NODAL DATA SUPPRESSED **** PRINT OF EQUATION NUMBERS SUPPRESSED **** FLUID FLOW CONVECTION IS INCLUDED IN THIS MODEL. [ 1] Input fluid flow result file for part: 7 Load Case: 10 Viscous Heating: 0 Turbulence: 1 **** HARD DISK FILE SIZE INFORMATION FOR PROCESSOR: Available hard disk space on C drive = 115962.301 megabytes **** LOAD CASE MULTIPLIERS Boundary temperature multiplier 1.000 Convection multiplier 1.000 Radiation multiplier 1.000 Heat generation multiplier 1.000 **** **** Invoking Enhanced Iterative Solver ... **** 11 5.677E-02m 11 5.677E-02m **** CONVERGED SOLUTION OBTAINED **** TEMPORARY FILE STORAGE (MEGABYTES) ---------------------------------- UNIT NO. 7 : 2.119 UNIT NO. 8 : 11.698 UNIT NO. 9 : 0.040 UNIT NO. 10 : 0.040 UNIT NO. 11 : 453.357 UNIT NO. 12 : 0.000 UNIT NO. 13 : 0.040 UNIT NO. 14 : 0.001 UNIT NO. 15 : 0.040 UNIT NO. 18 : 6.400 UNIT NO. 65 : 2.119 UNIT NO. 67 : 117.662 TOTAL : 593.515 **** End of File ****

[Joey.X]

Thanks for the log file. 

The log file shows that the Nonlinear control option is On and "FLUID FLOW CONVECTION IS INCLUDED". This is a stronger indication of possible non-converged result. For further diagnose, I need ds.lgs file which is "analysis log" in report tab, and it will be better to supply all the loading setups. Here are some possible check list. How about the flow convection setup? does it has loading from fluid analysis? check if the mesh is idential. Also check if the element types are "Brick" if all parts are solid parts.

[chikhlas]

How about the flow convection setup? does it has loading from fluid analysis?

yes it has been done from fluid flow analysis.

check if the mesh is idential. Also check if the element types are "Brick" if all parts are solid parts.

identical mesh 50%, all the parts are bricks in thermal analysis.

but the log file show that converged solution obtained.

i cant attach ds.lgs file here, it gives error that u can't attach this file. the details of thi file is as follows;

Autodesk (R) Simulation Steady-State Heat Transfer
Version 2012.01.00.0017-W64/X64 15-Jun-2011
Copyright (c) 2011, Autodesk, Inc. All rights reserved.

 **** Memory Dynamically Allocated =   1928538 KB
 **** Steady-State Heat Transfer Analysis
 
 ----------------------------------------------------------------
      DATE: AUGUST 29, 2011              
      TIME: 02:10 PM
      Input Model: C:\Users\Ikhlas\Documents\autocad\789.ds_data\8\ds


           PROGRAM VERSION: 201201000017
           ALG.DLL VERSION: 201201000017
     AlgConfig.DLL VERSION: 201201000017
      Agsdb_AR.DLL VERSION: 201201000017
      AMGSolve.DLL VERSION: 201201000017
      AlgSolve.DLL VERSION: 201201000017
 ----------------------------------------------------------------
 
      Options executed are:
      NOMIN
      SUPSTR
 
 
      processing ...
 

 **** Model Unit System Settings:
      --------------------------------------------
       Unit System              : Custom
       Force                    : N
       Length                   : mm
       Time                     : s
       Temperature (Absolute)   : deg C (K)
       Thermal Energy           : J
       Voltage                  : V
       Current                  : A
       Electrical Resistance    : ohm
       Mass                     : N*s^2/mm
      --------------------------------------------

 **** OPENING TEMPORARY FILES
      NDYN = 10
 **** BEGIN NODAL DATA INPUT
      Node     number=    277691
      Equation number=    277691
 **** END   NODAL DATA INPUT
 **** HARD DISK FILE SIZE INFORMATION FOR PROCESSOR:

      Available hard disk space on C drive = 115962.301 megabytes

 **** BEGIN NODAL HEAT FLOW INPUT
 **** END   NODAL HEAT FLOW INPUT

 ****
 **** Invoking Enhanced Iterative Solver ...
 ****


 **** BEGIN NON-LINEAR ITERATIONS

      Nonlin Iter.  Incr. Norm(T)  Rel. Norm(T)
      -----------   ------------   -----------
                1   1.977E+01      2.971E+00
                2   0.000E+00      0.000E+00

 **** END   NON-LINEAR ITERATIONS
 
 **** CONVERGED SOLUTION OBTAINED
 **** BEGIN TYPE-39 HEAT FLUX CALCULATIONS
      4541 ELEMENTS ...
 **** END   TYPE-39 HEAT FLUX CALCULATIONS
 **** BEGIN TYPE-39 HEAT FLUX CALCULATIONS
      15766 ELEMENTS ...
 **** END   TYPE-39 HEAT FLUX CALCULATIONS
 **** BEGIN TYPE-39 HEAT FLUX CALCULATIONS
      3448 ELEMENTS ...
 **** END   TYPE-39 HEAT FLUX CALCULATIONS
 **** BEGIN TYPE-39 HEAT FLUX CALCULATIONS
      111597 ELEMENTS ...
 **** END   TYPE-39 HEAT FLUX CALCULATIONS
 **** BEGIN TYPE-39 HEAT FLUX CALCULATIONS
      8317 ELEMENTS ...
 **** END   TYPE-39 HEAT FLUX CALCULATIONS
 **** BEGIN TYPE-39 HEAT FLUX CALCULATIONS
      8930 ELEMENTS ...
 **** END   TYPE-39 HEAT FLUX CALCULATIONS
 **** BEGIN TYPE-39 HEAT FLUX CALCULATIONS
      65693 ELEMENTS ...
 **** END   TYPE-39 HEAT FLUX CALCULATIONS
 **** BEGIN TYPE-39 HEAT FLUX CALCULATIONS
      11119 ELEMENTS ...
 **** END   TYPE-39 HEAT FLUX CALCULATIONS

 **** Table for actual hard disk space used:
      ds.t7  =    2169.469 kilobytes
      ds.t8  =   11978.438 kilobytes
      ds.t9  =      41.250 kilobytes
      ds.t10 =      41.250 kilobytes
      ds.t11 =  464237.246 kilobytes
      ds.t12 =       0.000 kilobytes
      ds.t13 =      41.250 kilobytes
      ds.t14 =       0.562 kilobytes
      ds.t15 =      41.250 kilobytes
      ds.t18 =    6553.125 kilobytes
      ds.t65 =    2169.469 kilobytes
      ds.t67 =  120485.934 kilobytes
 
      total temporary disk storage (megabytes) = 593.515
 
 **** BEGIN DELETING TEMPORARY FILES
 **** TEMPORARY FILES DELETED
 **** END OF SUCCESSFUL EXECUTION
 
 Processing completed for model C:\Users\Ikhlas\Documents\autocad\789.ds_data\8\ds
 
      ds.l10   =       3.871 kilobytes
      ds.to    =   13016.812 kilobytes
      ds.hfo   =    8065.402 kilobytes

      Total actual hard disk space used    =    621.983 megabytes

      Total elapsed time                   =     15.246 minutes

[Joey.X]

Nonlin Iter. Incr. Norm(T) Rel. Norm(T)
----------- ------------ -----------
1 1.977E+01 2.971E+00
2 0.000E+00 0.000E+00

The two nonlinear iteration is obviously not sufficient to get converged solution. 

It appears that the issue came from fluid convection which needs nonlinear iteration. Here are approach for touble-shooting.

- Disable fluid convection loading,and run again to see what happens.If the strange temperature pattern is gone, confirm the issue was from fluid convection

- Also thermal analysis/analysis parameter/Advanced tab, check the parameter settings for nonlinear iteration.

- Check fluid result to see if the pattern is reasonable, sometimes the too coarse density in fluid domain may cause solution stablity issue in thermal analysis.

BTW, "Analysis finished" does not always mean a good converged result, it may have false convergence depending on the model setups and model natures.

[chikhlas]

fluid flow analysis always gives warnings

Warning: Converge with stagnation due to oscillation

how can i overcome

[Joey.X]

It depends on model setup to decide whether to accept the result with warning of "Converge with stagnation due to oscillation”, below are two typical situations.

(a)One of the typical reasons is that the outlet or constant pressure is too close to flow obstacle or flow turning position where the pressure is far away from stable; enforcing an unphysical BC will cause solution instability.  This can be fixed by extending the flow simulation domain helps for this.

(b)In some physical cases where flow through obstacle in certain Reynolds number, the vortex shedding forms, it indicates no stable solution existed. Enforcing a steady state analysis may cause convergence oscillation; the result could be prone to average solution and usually be acceptable but needs attention.

Chikhlas, this sounds a different topic from the title of this thread. Please open a new thread for asking a new topic which is different from the original topic name.