Running Simulations

Running Simulations#

Once your simulation is configured, this page covers how to launch, monitor, and manage simulation runs.

Launching a Simulation#

Review your configuration in the Simulation tab:
- Solver type selected (density-based recommended)
- Turbulence model selected
- Boundary conditions assigned to all surfaces
- Solver settings configured
Click Run Simulation
A confirmation dialog shows:
- Estimated credit cost
- Mesh cell count
- Selected turbulence model
Click Confirm to submit the job

The simulation is queued and dispatched to cloud GPUs.

Job Status#

Your simulation progresses through these stages:

Status	Description
Pending	Job submitted, waiting for resources
Queued	Resources allocated, initializing
Running	Solver actively iterating
Completed	Converged or reached max iterations
Failed	Error occurred — check logs

The current status is displayed in the workspace header with color coding.

Monitoring Convergence#

Residual Plot#

While the simulation runs, the convergence plot updates in real time. The residuals shown depend on your solver type:

Density-based solver (default):

Density residual — Primary convergence indicator for the coupled system
Momentum residuals (ρu, ρv, ρw) — Momentum equation errors
Energy residual — Energy equation error
Turbulence residuals (k, ω or ε) — Turbulence model errors

Pressure-based solver:

Continuity residual — Mass conservation error
Velocity residuals (Ux, Uy, Uz) — Momentum equation errors
Turbulence residuals (k, ω or ε) — Turbulence model errors

All residuals are plotted on a logarithmic scale vs. iteration number.

What to look for:

Residuals should decrease monotonically (trending downward)
A converged solution shows residuals reaching a plateau at a low level
Oscillating residuals indicate the solution is struggling — consider adjusting CFL (density-based) or relaxation factors (pressure-based)

Convergence Indicators#

Residual Level	Meaning
> 1e-2	Not converged — solution is changing significantly
1e-2 to 1e-4	Partially converged — trends are established
< 1e-5	Well converged — engineering quantities are stable (density-based target)
< 1e-4	Well converged — suitable for pressure-based solver
< 1e-6	Tightly converged — research-grade accuracy

Tip

For engineering applications, convergence to 1e-5 (density residual) is usually sufficient. Force and moment coefficients typically stabilize well before residuals reach their final level — always verify that Cd, Cl, and pressure drop have plateaued.

Logs#

The Logs panel shows real-time solver output:

Iteration count and residual values
Solver diagnostics (limiter activity, CFL numbers)
Error messages if something goes wrong
Execution timing

Use the filter and search functions to find specific information in the log.

Simulation Completion#

When the simulation completes (converged or max iterations reached), you’ll see:

Final residual values — How far the solution converged
Total iterations — How many iterations were run
Runtime — Total wall-clock time
Credits used — Actual credit consumption

The results are automatically saved and available in the Results tab.

Failed Simulations#

If a simulation fails, check:

Logs — Error messages indicate the cause
Mesh quality — Poor mesh quality is the most common cause of failure
Boundary conditions — Inconsistent or missing BCs cause solver errors
Solver settings — Overly aggressive relaxation can cause divergence

Common Failure Causes#

Error	Cause	Fix
Floating point exception	Solution diverged	Reduce CFL (density-based) or relaxation factors (pressure-based)
Negative cell volume	Mesh error	Regenerate mesh, check geometry
Matrix singularity	Isolated cells or patches	Check mesh connectivity
Credit limit reached	Insufficient credits	Upgrade tier or wait for monthly reset

Re-Running#

You can re-run a simulation with modified settings:

Adjust parameters in the Simulation tab
Click Run Simulation again
Previous results remain accessible for comparison