Helpie FAQ

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  • FLO-2D runs on 64-bit Windows operating systems (Windows 7 or newer). For projects with approximately one million grid elements or more, a high-performance workstation such as a modern gaming-class system with a fast processor and multiple CPU cores can significantly reduce simulation runtimes. Single-core processor speed (greater than ~3 GHz) has the greatest impact on overall performance, while additional cores provide diminishing but still measurable benefits. In general, FLO-2D simulations tend to run efficiently on modern AMD processors.

    FLO-2D simulations may also be executed on server hardware. When running on a server, a Windows environment (physical, virtual, or containerized) is required. The FLOPRO.EXE executable, associated library and activator files, Intel runtime libraries, and Microsoft Visual Studio runtime packages must all be installed and accessible within the server environment to successfully execute a simulation.

    FLO-2D does not use graphical processing GPU system for the engine but the FLO-2D Plugin and QGIS does allow for GPU processing.

  • In theory, FLO-2D does not impose a fixed upper limit on the number of grid elements in a model domain. In practice, the feasible grid size is governed by model complexity, numerical stability, and available computational resources. Most large-scale FLO-2D simulations are on the order of 1–2 million grid elements. Simpler applications, such as uniform overland flow models with minimal hydraulic structures, have been successfully run with grids approaching 6 million cells.

    Grid cell size has a greater impact on model performance and stability than the absolute number of grid elements. Very small cells significantly increase computational cost and may lead to timestep restrictions or numerical instability. Guidance on selecting an appropriate grid cell size is discussed in the following question.

  • FLO-2D uses an integer-based grid cell size. Cell sizes smaller than approximately 10 ft (3 m) can increase the likelihood of numerical instability and may produce unreliable results. When using small grid cells, the output files TIME.OUT, VELTIMEFP.OUT, and ROUGH.OUT should be reviewed carefully to assess model stability and solution quality. Repeated occurrences of excessively high or erratic velocities in these files are a strong indication that the selected cell size is too small. Additional guidance is provided in the Grid Element Size Selection training package.

     

  • Begin by confirming that the software is properly activated. Verify the activation status and, if applicable, have IT run the annual activator to ensure the license is current.  In newer versions, the error.chk file will show the activation status.

    Review any Fortran error messages displayed during execution. These messages typically reference a specific input or output file associated with the failure. Use the referenced file name to locate the corresponding troubleshooting guidance in the Data Input Manual.  For example, if a file is locked by another program, a Fortran error message will indicate that the file is locked.

    The ERROR.CHK file (or STORMDRAIN.ERROR.CHK for storm drain simulations) should also be reviewed. These files contain fatal error messages along with brief descriptions of the issue and recommended correction steps. The same errors and resolution guidance are documented in the Data Input Manual troubleshooting section.

    If the issue cannot be resolved using these steps, submit a request through the FLO-2D contact form.  Include a brief description of the problem and any files listed by the Fortran Error Message.

    Don’t forget that simple troubleshooting starts by assessing the last modeling modification.  It is generally the cause of the problem.

  • If a simulation begins successfully but terminates before the expected completion time, the model typically progresses until it encounters a problematic grid element or data condition. In these cases, simplify the simulation by temporarily disabling model components and performing targeted test runs. Running individual components such as boundary conditions, culverts, or channels independently can help isolate the source of the failure.

    If the simulation terminates with a FORTRAN 157 error code, the termination is usually related to an interruption in data processing rather than a modeling error. To reduce the likelihood of this type of failure, ensure that the computer does not enter sleep mode, apply automatic operating system updates, or run background processes that could disrupt file access. Running the simulation in Text Mode, disabling time-series output, and avoiding execution from external or network-mounted drives can also reduce processing disruptions from systems.

    When running FLO-2D on a server or virtual machine, the same precautions apply. The server environment should be protected from automatic resets, updates, or other processes that may interrupt file I/O during the simulation.

    If cloud synchronization tools such as OneDrive or Google Drive are in use, simulations should be executed from a path that is not actively synchronized to a cloud or external storage location. Active syncing can interfere with file access and cause premature termination.

  • The error message will reference a specific data file. Use the Data Input Manual Chapter 4 to see if the file is set up correctly. Each data file can be opened in NotePad or NotePad++.

    If the error message references an output file, check that the location of the run is allowed. It could be locked because a file is opened in another program. It could be that the Path does not have read/write privileges. For example, running models on the Company Servers can may have write restrictions that local machines do not have.

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