Message 10093

TUFLOW FV

Available since version: 2026.2.0

ERROR 10093 - Velocity has exceeded stability limit <velocity_stability_limit> (m/s or ft/s) at 2D cell <2d_cell_id>

Description

The velocity at the cell shown has exceeded the configured stability limit during the simulation. This may indicate numerical instability which has caused the solution to diverge at this location. The velocity stability limit is the second argument set using Stability Limits ==.

Suggestions

The stability limits can be adjusted using the Stability Limits == command in the model control file. Ensure that the specified velocity limit argument reflects the expected flow conditions being investigated. A velocity limit of 10 m/s is commonly used.

The simulation time at which the error occurs may help to diagnose the issue. If the error occurs early in the simulation or at initialisation, it is likely a model configuration, initial condition or boundary condition mismatch. If the error occurs later during the simulation and the model configuration appears correct, the region surrounding the offending 2d cell(s) warrants further investigation for instabilities.

For model instability, review the model setup in the vicinity of the cell shown in the GIS messages output file. Common causes include a timestep that is too large for the mesh resolution, poor mesh quality near the affected cell and extreme or incorrectly specified boundary conditions.

While the error will be reported at the first cell that exceeds the specified stability limit, the root case may originate from a different cell, typically close by. To track where velocity divergence begins, it may be useful to add a secondary output block with high temporal resolution at a time just prior to when the error occurs. For example, if the model crashes at 02/12/2008 21:15:36:

Output == NetCDF 
    Suffix == CHK                             ! For checking
    Output Parameters == h, v                 ! Water level, velocity
    Start Output == 02/12/2008 21:15:00       ! Time close to the error occurrence
    Final Output == 02/12/2008 21:17:00       ! Time immediately after the crash, mainly for safety so the model cannot continue writing high temporal resolution output AND FILL UP RESULT STORAGE. BE CAREFUL!!!!
    Output Interval == 1                      ! (s) High temporal resolution output to help track initial cell where instability starts and propagation
End Output

This block writes water level and velocity at 1 second intervals (0 will use the model timestep if higher temporal resolution is required) in a narrow window around the error. Stepping through the output in time allows identification of the initial cell where instability begins and its propagation path.

The command Write Restart At Time == can also be useful to start a follow-up run close to the time of the error.