TUFLOW Message 1991: Difference between revisions

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|alt_msg=WARNING 1991 - ",a,": Negative depth at Node ",a,": "," y =",f7.2," Bed =",f7.2," dh =
|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. Note There arethat a numberseparate ofwarning possibleis reasonissued for thisconvergence toissues occur,in the most2D domain (see <u>[[TUFLOW Message common2991|Message are:2991]]<br/u>).
 
Incorrect bed levels upstream or downstream;<br>
|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>
A large change in cross-sectional area;<br>
* Incorrect bed levels upstream or downstream;<br>
Very steep channel entering a gently or advers grade channel;<br>
* A large change in cross-sectional area;<br>
Sudden change in flow area (for example a culvert width entered in mm not m, 1200 not 1.2);<br>
* Very steep channel entering a gently or adversadverse grade channel;<br>
Issues with 1D/2D linking (incorrect use of Z flag on culvert inlet / outlet);
* Sudden change in flow area (for example a culvert width entered in mm not m, 12001200mm notrather than 1.22m);<br>
To high a timestep; and<br>
* Issues with 1D/2D linking (incorrect use of Z flag on culvert inlet / outlet);
Low nodal area.<br>
To* Too high a timestep; and<br>
Low* Too small a nodal area.<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).
 
|suggestions=Identify start of instability and cause of instability and fix! See references above for guidance.
|discussion_page=* [[Talk:TUFLOW Message 1991|Discuss Message 1991]]
|link3=''