Computation error Minimum error exceeds allowable tolerance

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Computation error Minimum error exceeds allowable tolerance

tika
HI, could anyone help me with this problem?

 I run unsteady flow simulation and the program show the computation message
Performing Unsteady Flow Simulation  HEC-RAS 5.0.3 September 2016

   ****   ERROR:  Solution Solver Failed   ****

Minimum error exceeds allowable tolerance at   11FEB2014   01:00:00

kali surabaya   1               7.3000*

 

   ****   The Model Has One Or More Error(s)   ****

Unsteady Flow Simulation Terminated
 
Writing Results to DSS
Finished Writing Results to DSS

Reading Data for Post Process
    Simulation went unstable at: 11Feb2014 01:01:00
       
Running Post Processor  HEC-RAS 5.0.3 September 2016

Finished Post Processing


Stored maps were not written because the simulation did not complete.


Computations Summary

Computation Task Time(hh:mm:ss)
Completing Geometry <1
Preprocessing Geometry(64) <1
Unsteady Flow Computations(64) <1
Writing to DSS(64) <1
Post-Processing(64) <1
Complete Process       1

****
What should I do ?
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Re: Computation error Minimum error exceeds allowable tolerance

Mohsin
Hi,
Did you find any solution for this problem. I am getting the similar kind of errors. Thanks
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Re: Computation error Minimum error exceeds allowable tolerance

cameron
The model stopped because the minimum error tolerance was exceeded. This could be caused by a number of things, incorrect time step, need for additional cross-sections, more ineffective flow areas.

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Re: Computation error Minimum error exceeds allowable tolerance

Mohsin
thanks, model is running now but still it is showing warnings and errors related to WSEL? how to fix them or we can ignore it?
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Re: Computation error Minimum error exceeds allowable tolerance

Keith M
HEC-RAS writes errors and warnings in 1) the computation messages shown in the unsteady flow analysis window, and 2) under the cross-section results.

When running an unsteady flow analysis, the WSEL errors shown under the compute messages don't necessarily need to be addressed.  The general guidance I have heard is that WSEL errors in the 0.1 to 0.3 range, or lower, are usually okay.  However, that pertains only to the WSEL errors.  Other errors and warnings may be written after the unsteady computations have been completed, but before the post processing begins.  These are highlighted in red and should be addressed.  

Warnings in the cross-section results don't always need to be addressed, but the errors should be.
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Re: Computation error Minimum error exceeds allowable tolerance

Mohsin
Thanks for the answer. I still have following errors, it would be nice if you could explain/guide how to resolve them.

Performing Unsteady Flow Simulation  HEC-RAS 5.0.3 September 2016

Maximum iterations of 20               RS WSEL ERROR

27MAY2006 00:00:00  Upper Main       Reach 1         415500.0  249.05   0.027

*****  Warning!  Extrapolated above Cross Section Table at:  *****

    Upper Main Reach 1    from R.S.   464900.0  to  462600.0
    Upper Main Reach 1    from R.S.   462300.0  to  462125.7
    Upper Main Reach 1    R.S.   461536.1
    Upper Main Reach 1    from R.S.   460924.6  to  457298.1
    Upper Main Reach 1    from R.S.   456896.6  to  454362.4
    Upper Main Reach 1    from R.S.   453618.5  to  452561.9
    Upper Main Reach 1    from R.S.   451953.4  to  449385.0
    Upper Main Reach 1    from R.S.   447410.4  to  446212.0
    Upper Main Reach 1    from R.S.   445626.5  to  445443.3
    Upper Main Reach 1    from R.S.   445031.9  to  442255.0
    Upper Main Reach 1    from R.S.   441681.5  to  440492.1
    Upper Main Reach 1    R.S.   439917.8
    Upper Main Reach 1    from R.S.   437907.4  to  437673.5
    Upper Main Reach 1    R.S.   436905.4
    Upper Main Reach 1    from R.S.   435119.1  to  434909.1
    Upper Main Reach 1    from R.S.   434099.6  to  433709.1
    Upper Main Reach 1    R.S.   433364.2
    Upper Main Reach 1    R.S.   432535.3
    Upper Main Reach 1    from R.S.   415869.3  to  415828.3
    Upper Main Reach 1    R.S.   410250.9
    Upper Main Reach 1    from R.S.   407949.4  to  407754.0
    Upper Main Reach 1    from R.S.   407200.6  to  407156.4
    Upper Main Reach 1    R.S.   406200.0
    Upper Main Reach 1    R.S.   406082.0
    Upper Main Reach 1    R.S.   404631.2
    Upper Main Reach 1    from R.S.   395179.0  to  395144.0
    Upper Main Reach 1    R.S.   395076.9

 

The maximum xsec wsel error was     0.088
Upper Main  Reach 1  415500.0  at  27MAY2006 00:00:00

   ****   The Model Has One Or More Warning(s)   ****


Thanks :-)
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Re: Computation error Minimum error exceeds allowable tolerance

Keith M
The extrapolation warnings mean that the maximum WSEs were calculated to be greater than the maximum elevation applied to the hydraulic property table that corresponds to each cross-section listed under the warning.  

This can be corrected by manually increasing the maximum elevations in the HTab Parameter table editor in the geometry file.  
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Re: Computation error Minimum error exceeds allowable tolerance

Mohsin
Hi, i tried with different values in Htab parameters ( i simply increase the 'increment' tab value, is this the right way?) along with it there are still some warnings in the cross-sections. Few of them are listed below. Can you please explain which if them i need to address and how?



Location: River: Upper Main  Reach: Reach 1     RS: 463300.0     Profile: Max WS
Warning:  The cross-section end points had to be extended vertically for the computed water surface.
Location: River: Upper Main  Reach: Reach 1     RS: 463200.0     Profile: Max WS
Warning:  The cross-section end points had to be extended vertically for the computed water surface.
Location: River: Upper Main  Reach: Reach 1     RS: 463100.0     Profile: Max WS
Warning:  The cross-section end points had to be extended vertically for the computed water surface.
Location: River: Upper Main  Reach: Reach 1     RS: 463000.0     Profile: Max WS
Warning:  The cross-section end points had to be extended vertically for the computed water surface.
Warning:  The conveyance ratio (upstream conveyance divided by downstream conveyance) is less than 0.7
          or greater than 1.4.  This may indicate the need for additional cross sections.
Location: River: Upper Main  Reach: Reach 1     RS: 462900.0     Profile: Max WS
Warning:  The cross-section end points had to be extended vertically for the computed water surface.
Warning:  The conveyance ratio (upstream conveyance divided by downstream conveyance) is less than 0.7
          or greater than 1.4.  This may indicate the need for additional cross sections.
Location: River: Upper Main  Reach: Reach 1     RS: 462800.0     Profile: Max WS
Warning:  The cross-section end points had to be extended vertically for the computed water surface.
Warning:  The energy loss was greater than 1.0 ft (0.3 m). between the current and previous cross section.  
          This may indicate the need for additional cross sections.
Location: River: Upper Main  Reach: Reach 1     RS: 462700.0     Profile: Max WS
Warning:  The cross-section end points had to be extended vertically for the computed water surface.
Warning:  The energy loss was greater than 1.0 ft (0.3 m). between the current and previous cross section.  
          This may indicate the need for additional cross sections.
Location: River: Upper Main  Reach: Reach 1     RS: 462600.0     Profile: Max WS
Warning:  The cross-section end points had to be extended vertically for the computed water surface.
Warning:  The conveyance ratio (upstream conveyance divided by downstream conveyance) is less than 0.7
          or greater than 1.4.  This may indicate the need for additional cross sections.
Location: River: Upper Main  Reach: Reach 1     RS: 462500.0     Profile: Max WS
Warning:  The cross-section end points had to be extended vertically for the computed water surface.
Location: River: Upper Main  Reach: Reach 1     RS: 462400.0     Profile: Max WS
Warning:  The cross-section end points had to be extended vertically for the computed water surface.
Location: River: Upper Main  Reach: Reach 1     RS: 462300.0     Profile: Max WS
Warning:  The cross-section end points had to be extended vertically for the computed water surface.
Warning:  The velocity head has changed by more than 0.5 ft (0.15 m).  This may indicate the need for
          additional cross sections.
Warning:  The conveyance ratio (upstream conveyance divided by downstream conveyance) is less than 0.7
          or greater than 1.4.  This may indicate the need for additional cross sections.
Location: River: Upper Main  Reach: Reach 1     RS: 462125.7     Profile: Max WS
Warning:  The cross-section end points had to be extended vertically for the computed water surface.
Warning:  The velocity head has changed by more than 0.5 ft (0.15 m).  This may indicate the need for
          additional cross sections.
Warning:  The energy loss was greater than 1.0 ft (0.3 m). between the current and previous cross section.  
          This may indicate the need for additional cross sections.


Thanks again for your suggestions.