Tutorial: Using a File-Based Grid (Bent Channel)

Table of Contents

• 1. Initialize a Study
• 2. File-Grid Configuration
• 3. Run the Case
• 4. Visualize Results
• 5. Next Steps
  • CFD Reader Guidance and Practical Use
    • What To Extract Before Changing A Case
    • Practical CFD Troubleshooting Pattern

This tutorial demonstrates grid.mode: file using the bent_channel template.

1. Initialize a Study

./bin/picurv init bent_channel --dest my_bent_channel_run

Expected files:

my_bent_channel_run/
|- bent_channel.yml
|- Imp-MG-Standard.yml
|- Standard_Output.yml
|- standard_analysis.yml
|- bent_channel_coarse.picgrid
|- bent_channel_coarse.vts
`- bent_channel_coarse.info

2. File-Grid Configuration

In bent_channel.yml:

grid:
  mode: file
  source_file: bent_channel_coarse.picgrid

Behavior:

• picurv validates the source grid file exists.
• Coordinates are non-dimensionalized before C execution using properties.scaling.length_ref.
• Generated normalized grid is staged into run config artifacts.

For geometric-periodic file grids, the runtime additionally verifies that each paired surface matches pointwise under one nonzero constant translation and that the periodic axis has at least four physical nodes.

3. Run the Case

./bin/picurv run \
    --case my_bent_channel_run/bent_channel.yml \
    --solver my_bent_channel_run/Imp-MG-Standard.yml \
    --monitor my_bent_channel_run/Standard_Output.yml \
    --post my_bent_channel_run/standard_analysis.yml \
    -n 4 --solve --post-process

4. Visualize Results

1. Open runs/<run_id>/viz/Field_*.vts.
2. Use Stream Tracer seeded near inlet.
3. Color by Ucat_nodal magnitude.

This provides a fast sanity check of bend-flow behavior.

5. Next Steps

Proceed to Tutorial: A Guide to Visualizing Your Results.

CFD Reader Guidance and Practical Use

This page describes Tutorial: Using a File-Based Grid (Bent Channel) within the PICurv workflow. For CFD users, the most reliable reading strategy is to map the page content to a concrete run decision: what is configured, what runtime stage it influences, and which diagnostics should confirm expected behavior.

Treat this page as both a conceptual reference and a runbook. If you are debugging, pair the method/procedure described here with monitor output, generated runtime artifacts under runs/<run_id>/config, and the associated solver/post logs so numerical intent and implementation behavior stay aligned.

What To Extract Before Changing A Case

• Identify which YAML role or runtime stage this page governs.
• List the primary control knobs (tolerances, cadence, paths, selectors, or mode flags).
• Record expected success indicators (convergence trend, artifact presence, or stable derived metrics).
• Record failure signals that require rollback or parameter isolation.

Practical CFD Troubleshooting Pattern

1. Reproduce the issue on a tiny case or narrow timestep window.
2. Change one control at a time and keep all other roles/configs fixed.
3. Validate generated artifacts and logs after each change before scaling up.
4. If behavior remains inconsistent, compare against a known-good baseline example and re-check grid/BC consistency.