Troubleshooting

Common issues and their solutions when working with Gradient Dynamics Studio.

Geometry Issues

“Geometry is not watertight”

Cause: Gaps between faces in the surface mesh.

Solutions:

1. For STL/OBJ files: Run vertex welding in the Geometry tab. This merges nearby vertices that should be connected.

2. For STEP/IGES files: Run CAD healing to sew adjacent faces.

3. If welding doesn’t fix it: The geometry has genuine holes. Run hole filling to patch them.

4. If issues persist: Return to your CAD software and fix the model.

“Non-manifold edges detected”

Cause: An edge is shared by more than two faces (T-junction topology) or faces overlap.

Solutions:

1. Run non-manifold edge repair — Studio will remove duplicate faces near problem edges.

2. In severe cases, simplify the geometry in your CAD tool to eliminate the topology issue.

“Geometry is very large/small”

Cause: Incorrect units — the geometry was exported in millimeters, inches, or another unit instead of meters.

Solutions:

1. Re-export the geometry in meters from your CAD software

2. Scale the geometry in your CAD tool before upload

Meshing Issues

Mesh generation fails

Possible causes and solutions:

Cause	Solution
Non-watertight geometry	Fix geometry first (see above)
Cell size too small for geometry	Increase minimum cell size
Too many refinement levels	Reduce to 8–10 levels
Complex geometry features	Simplify small features in CAD

Very high cell count

Cause: Cell size is too small relative to the domain, or excessive refinement.

Solutions:

1. Increase the target cell size

2. Reduce refinement levels

3. Use refinement zones instead of global refinement

4. Enable symmetry to halve the domain

Poor mesh quality (high skewness)

Cause: Complex geometry features or extreme size transitions.

Solutions:

1. Increase refinement levels (smoother transitions)

2. Add refinement zones near problem areas

3. Reduce boundary layer growth rate

4. Simplify geometry features near the problem area

Boundary layers fail to generate

Cause: Insufficient space between surfaces, or geometry issues preventing layer growth.

Solutions:

1. Check for narrow gaps between surfaces — layers from opposite walls can collide

2. Reduce the number of layers or first layer height

3. Ensure the geometry is clean near wall surfaces

Simulation Issues

Simulation diverges immediately

Cause: Usually aggressive relaxation or very poor mesh quality.

Solutions:

1. Reduce relaxation factors by 30% (velocity: 0.5→0.3, pressure: 0.2→0.15)

2. Enable turbulence ramping (delay turbulence activation by 50 iterations)

3. Check mesh quality — fix any cells with skewness > 0.95

4. Verify boundary conditions are physically consistent

Residuals oscillate but don’t decrease

Cause: The solver is struggling with the numerics or the flow is inherently unsteady.

Solutions:

1. Reduce relaxation factors

2. Enable non-orthogonal correctors if mesh quality is moderate

3. For inherently unsteady flows (e.g., bluff body vortex shedding), the flow may not have a steady-state solution — consider transient simulation

4. Check that boundary conditions don’t conflict

Residuals plateau at a high level (e.g., 1e-2)

Cause: The mesh may be too coarse, boundary conditions may be inconsistent, or the solver is hitting stability limits.

Solutions:

1. Refine the mesh in areas of high gradients

2. Check boundary conditions for consistency (e.g., mass flow in = mass flow out)

3. Review the logs for limiter warnings — extensive velocity clamping suggests the mesh needs refinement

4. Try a more robust turbulence model (k-ω SST if not already using it)

Unrealistic pressure or velocity values

Cause: Poor boundary conditions, mesh errors, or insufficient convergence.

Solutions:

1. Check inlet velocity and outlet pressure values

2. Verify the geometry scale (wrong scale = wrong Reynolds number)

3. Ensure the simulation has converged (check residual plot)

4. Check for negative cell volumes in the mesh quality report

Simulation takes too long

Cause: Very large mesh, slow convergence, or excessively tight criteria.

Solutions:

1. Reduce mesh size (start coarser)

2. Increase relaxation factors slightly (if convergence is stable)

3. Relax convergence criteria (1e-4 is adequate for most engineering applications)

4. Reduce max iterations and check if results are already stable

Post-Processing Issues

Results look wrong or asymmetric

Possible causes:

1. Insufficient convergence — Run more iterations

2. Asymmetric mesh — Check that the mesh is symmetric for a symmetric problem

3. Wrong boundary conditions — Verify all surfaces have correct conditions

4. Physical asymmetry — Some flows are genuinely asymmetric (vortex shedding, flow bifurcation)

Force coefficients seem too high or too low

Check:

1. Reference area — Is it correct? Drag uses frontal area; lift uses planform area.

2. Reference velocity — Must match the inlet freestream velocity

3. Surface selection — Are you measuring forces on the correct surfaces?

4. Convergence — Forces may not have converged even if residuals look okay. Run more iterations.

Account and Platform Issues

“Credit limit reached”

Your credit balance has been exhausted.

Solutions:

1. Wait for monthly credit reset

2. Upgrade to a higher tier for more credits

3. Optimize your workflow — use coarser meshes for initial setup, fine meshes only for final analysis

Mesh generation or simulation stuck in “Pending”

Cause: Cloud compute resources are being allocated.

Solutions:

1. Wait a few minutes — resource allocation may take time during peak usage

2. Check the status periodically

3. Contact support if the job is stuck for more than 15 minutes

Getting Help

If these troubleshooting steps don’t resolve your issue:

1. Ask the AI Assistant — Describe the problem in natural language

2. Check the logs — Detailed error messages are in the Logs panel

3. Contact support — Include your project ID and a description of the issue