A Model Won't Start

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This page provides common reasons why a model may fail to start and troubleshooting tips to fix them.

Reviewing The Log File

You may find that your simulation has crashed, or some other syntax error in the inputs has caused it to stop. If this happens, open the log file (*.log) to see what may have gone wrong. Be logical and thoughtful in your model preparation; often it’s a simple mistake that causes the most frustration.

The most efficient way to debug an input error is to work backward through the log file, searching for the following terms:

  • Unrecognised

A message will be written to the log file describing the input error.

Syntax Errors (Unrecognised Flag Encountered)

The most common issue experienced by new users when setting up a new model are often related to syntax errors. A message similar to that shown below will be written to the log file if input sytax is specified which is not recognised by TUFLOW FV.

Unrecognised flag encountered on line 15
Start Time = 0

In this instance, the syntax error is located on line 15 of the control file (fvc). The user has specified the command 'Start Timestep = 0'. Although the command is correct, the syntax is not. TUFLOW requires that two equals sign be used. The correct syntax is 'Start Time == 0'

Syntax highlighting is an effective way to differentiate between comments, commands and syntax errors. The following links step through how to install TUFLOW FV syntax highlighting:

UE Syntax Highlighting.png

Nodestrings And Boundary Conditions Don't Match (Unexpected Nodestring ID)

A message similar to the one shown below will be written to the log file if a boundary condition ID is specified in the TUFLOW control file (*fvc), though does not exist in the geometry 2dm file.

BC 2, Type=WL
ERROR:fvdomain_construct:init_bc:fvbc_construct:fvbc_construct:Unexpected nodestring id in bc 2

There are two ways to check the 2dm file and make sure that the nodestring you are assigning a boundary condition to is the correct one.

  • Within SMS, use the “Select Nodestring” tool in the Mesh module and click on the nodestring that you intend to be the boundary condition. On the display bar at the bottom of the SMS window the nodestring ID will be displayed; this is the nodestring ID to use in the TUFLOW FV control file (*.fvc).

EE Nodestring ID 001.png

  • Open the 2dm file in a text editor and search for “NS” at the start of the line. The NS lines provide a list of nodes that define the specific nodestring. The final node on a nodestring has a “-“ prefix, then the following number is the nodestring ID. It is this last number, the nodestring ID, that TUFLOW FV uses to identify the boundary condition.

NOTE: Nodestring order does not influence open boundaries; inflow (into the model domain) is assigned positive and outflow (out of the model domain) is negative irrespective of the node order in the nodestring.

EE Nodestring ID 002.png

In both of the above examples, the nodestring ID was '2'. This is the ID which needs to be specified in the TUFLOW FV control file (*.fvc), relating the water level boundary condition timeseries data to the nodestring location.

EE Nodestring ID 003.png

File Reference Errors (Unable To Open File)

Specifying an incorrect reference to a file will produce an error. The following message will be written to the log file.

Trying to open file: D:\TUFLOW_FV\Error_Example\bc\Flow_001.csv ...NOT OK
Unable to open file: D:\TUFLOW_FV\Error_Example\bc\Flow_001.csv

Correcting the filepath reference will fix the model intilisation error.

Filepath referencing can be checked from the TUFLOW FV Control file (*.fvc), prior to running the simulation. Directions how to configure UtraEdit and Notepad++ to do this can be found here:

Geometry File Input Error (Linear Elements Only Expected)

TUFLOW FV requires linear element geometry mesh (*.2dm) inputs. A linear element mesh is represented by any combination of triangular or quadrilateral elements with node elevations specified at each vertex. In contrast, a quadratic mesh type includes node elevations specified at each vertex and also at the centre of each element face.

EE LMesh 00.png

TUFLOW FV cannot use quadratic mesh type geometry inputs. If used, the model will not initialise and the following error message will be reported in the model log file:

Processing mesh geometry file/s:
Reading 2dm mesh file...
Trying to open file: D:\TUFLOW_FV\Error_Example\RiverBend_Mesh001_Midside.2dm ... OK. File unit: 101

ERROR:fvdomain_construct:init_dmn:fvmesh_construct:fvmesh_rd2dm:Linear elements only expected

A quadratic mesh can be converted to a linear mesh using SMS. To do this:

  • Select the Mesh Data Coverage
  • Select Elements > Linear<->Quadratic

EE LMesh 01.png

If you have further queries please email support@tuflow.com.