Difference between revisions of "TUFLOW Message 1991"

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|alt_msg=WARNING 1991 - ",a,": Negative depth at Node ",a,": "," y =",f7.2,"  Bed =",f7.2,"  dh =
 
|alt_msg=WARNING 1991 - ",a,": Negative depth at Node ",a,": "," y =",f7.2,"  Bed =",f7.2,"  dh =
 
|type=[[WARNING]]
 
|type=[[WARNING]]
|message_desc=Numerical solution has resulted in a negative depth at 1D node.  This indicates that the model is unstable or unhealthy in this area. There are a number of possible reason for this to occur, the most common are:<br>
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|message_desc=Numerical solution has resulted in a negative depth at 1D node.  This indicates that the model is unstable or unhealthy in this area. Note that a separate warning is issued for convergence issues in the 2D domain (see <u>[[TUFLOW Message 2991|Message 2991]]</u>).
Incorrect bed levels upstream or downstream;<br>
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A large change in cross-sectional area;<br>
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|suggestions=Import the messages layer in to your GIS package.  Check for the number and time at which these warnings occur. A few warnings at a single location or timestep in the simulation are not normally an issue. Persistent warnings however warrant further investigation. Check the following: <br>
Very steep channel entering a gently or advers grade channel;<br>
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* Incorrect bed levels upstream or downstream;<br>
Sudden change in flow area (for example a culvert width entered in mm not m, 1200 not 1.2);<br>
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* A large change in cross-sectional area;<br>
Issues with 1D/2D linking (incorrect use of Z flag on culvert inlet / outlet);
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* Very steep channel entering a gently or adverse grade channel;<br>
To high a timestep; and<br>
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* Sudden change in flow area (for example a culvert width entered in mm not m, 1200mm rather than 1.2m);<br>
Low nodal area.<br>
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* Issues with 1D/2D linking (incorrect use of Z flag on culvert inlet / outlet);
 +
* Too high a timestep; and<br>
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* Too small a nodal area.<br>
 
<br>
 
<br>
For a more detailed description on identify the start of instability please see Section 8.1.3 Tips for an Unhealthy 1D Domain and Section 8.1.4 Tips for Unhealthy 1D/2D Links of the TUFLOW manual (reference for 2010 version).
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For a more detailed description on identify the start of instability, refer to the <u>[https://docs.tuflow.com/classic-hpc/manual/latest/ TUFLOW Manual]</u>.
|suggestions=Identify start of instability and cause of instability and fix!  See references above for guidance.
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|discussion_page=* [[Talk:TUFLOW Message 1991|Discuss Message 1991]]
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|link3=''
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|link4=''
 
|prelink=[[TUFLOW_Message_1527|Message 1527]]
 
 
|uplink=[[1xxx_TUFLOW_Messages|1xxx Messages]]
 
|uplink=[[1xxx_TUFLOW_Messages|1xxx Messages]]
|nextlink=[[TUFLOW_Message_1998|Message 1998]]
 
 
}}
 
}}

Latest revision as of 09:57, 23 September 2024

TUFLOW Message
WARNING 1991 - ",a,": Negative depth at Node ",a,": "," y =",f7.2," Bed =",f7.2," Iter =

Alternate Message
WARNING 1991 - ",a,": Negative depth at Node ",a,": "," y =",f7.2," Bed =",f7.2," dh =

Message Type
WARNING

Description
Numerical solution has resulted in a negative depth at 1D node. This indicates that the model is unstable or unhealthy in this area. Note that a separate warning is issued for convergence issues in the 2D domain (see Message 2991).

Suggestions
Import the messages layer in to your GIS package. Check for the number and time at which these warnings occur. A few warnings at a single location or timestep in the simulation are not normally an issue. Persistent warnings however warrant further investigation. Check the following:

  • Incorrect bed levels upstream or downstream;
  • A large change in cross-sectional area;
  • Very steep channel entering a gently or adverse grade channel;
  • Sudden change in flow area (for example a culvert width entered in mm not m, 1200mm rather than 1.2m);
  • Issues with 1D/2D linking (incorrect use of Z flag on culvert inlet / outlet);
  • Too high a timestep; and
  • Too small a nodal area.


For a more detailed description on identify the start of instability, refer to the TUFLOW Manual.


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