TUFLOW Message 2991: Difference between revisions

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|alt_msg=WARNING 2991 - Negative V depth at ",a,".
|type=[[WARNING]]
|message_desc=A 2D negative depth has occurred at the cell side. This indicates the solution failed to converge at this point in the 2D domain and is an indicator that the model may become unstable. Note that a separate warning is issued for convergence issues in the 1D domain (see <u>[[TUFLOW Message 1991|Message 1999]]</u>).
|suggestions=Import the messages layer in to your GIS package. ACheck negativefor depth can be caused by athe number ofand things, looktime at thewhich '''_zpt_check'''these filewarnings tooccur. seeA iffew therewarnings isat a steepsingle changelocation inor topography,timestep in the '''uvpt_check'''simulation showsare thenot Manning'snormally nan valueissue. atPersistent warnings however eachwarrant cellfurther sideinvestigation. Check thisthe roughnessfollowing: suitable.<br>
* Look at the '''_zpt_check''' file to see if there is a steep change in topography. Where appropriate, smoothing out the topography or increasing the roughness may help stabilise the model.
A negative depth can also be caused by a badly behaving boundary condition nearby, check if this is occurring near a boundary. This can be 1D/2D, a external 2d (such as a HQ boundary) or a 2D/2D boundary.<br>
* Look at the '''uvpt_check''' file which shows the Manning's n value at each cell side. Check this roughness is suitable.<br>
View the velocity vectors prior to the message are the flow patterns realistic.<br>
A* negativeRepeated depthwarnings canmay alsooccur bedue caused by ato badly behaving boundary conditionconditions nearby, check if this is occurring near a boundary. This can be 1D/2D, a external 2d (such as a HQ boundary) or a 2D/2D boundary.<br>
This could also be an indicator of a timestep that is too large. However before reducing the timestep check the suggestions above!
* View the velocity vectors prior to the message are, verifying that the flow patterns are realistic.<br>
This* couldCheck alsothat be an indicator of athe timestep that is not too large., Howeverhowever beforerather than simply reducing the timestep, first check the suggestions above!
 
|discussion_page=* [[Talk:TUFLOW Message 2991|Discuss Message 2991]]
|link3=''