Monitoring Progress and the Solver

This chapter covers how LeaRes monitors a running simulation, how the MOEBIUS Lattice Boltzmann solver computes the flow, and how to troubleshoot common simulation problems.

Monitoring Progress

LeaRes monitors the run using probes placed in the flow. The solver tracks the time history of velocity and pressure at these probe locations and inspects them for convergence.

• The job percentage advances as the run proceeds
• When autoDuration is enabled, the run stops early once the probe data shows the flow has reached stationarity
• When the job reaches 100%, the results are ready to load (covered in the next tutorial)

How MOEBIUS Solves the Flow

Understanding the solver helps set realistic expectations:

• MOEBIUS is a Lattice Boltzmann (LBM) solver and is intrinsically transient — it always marches forward in time. A “steady” result is one where the time-evolving fields have stopped changing.
• Convergence is measured at the macroscopic level through probe monitoring of velocity and pressure, not through per-equation residuals. LBM evolves a single distribution function, so there is no separate U/V/W/P residual to watch.
• The time step is chosen internally by the solver to respect LBM stability constraints; you control the duration and resolution, not Δt.
• No subgrid turbulence model is active in the standard launch path: production runs are unmodelled (direct LBM). The solver implements Smagorinsky, Shear-Improved Smagorinsky and an ADM filter, but LeaRes does not enable them — fine features must be resolved by the grid. There are also no pressure-velocity coupling knobs such as SIMPLE or PISO; those belong to a different class of solvers.

Tip: Start with a coarser GridResolution to verify your setup runs and produces sensible flow, then increase resolution for a production run.

Troubleshooting

Job Stays at 0%

Problem: The job was created but does not progress.

Solutions:

• Make sure you clicked Simulate to launch the run
• Confirm boundaries (at least one inlet and one outlet) and a fluid are defined
• If a Confirm prompt appeared when adding the job, ensure it was acknowledged

Run Takes Too Long

Problem: The simulation is slow to reach 100%.

Solutions:

• Lower the GridResolution for faster iterations
• Enable autoDuration so the run stops as soon as the flow converges
• Reduce FramesGranularity to Last frame if you do not need intermediate frames

Results Look Unphysical

Problem: The flow does not match expectations.

Solutions:

• Recheck inlet velocity and outlet pressure on the boundaries
• Verify the inlet and outlet are painted at the correct openings
• Increase GridResolution if fine flow features are under-resolved

Next Steps

Once the job reaches 100%, you’re ready to explore the flow field. Continue to Visualizing Results.