Version: v0.4.3

1. Introduction

CFD Convergence Watch is a tool for visualizing and analyzing convergence history of monitor points from CFD (Computational Fluid Dynamics) simulations.

Load output files from various CFD solvers, view convergence trends on interactive charts, and evaluate convergence using Simple Moving Average (SMA) comparisons.

Supported Solvers

File Format Summary

Generic CSV — Comma-delimited. First column is X-axis.

timestep, var1, var2
1, 0.001, 0.002
2, 0.001, 0.002

Ansys CFX — Comma-delimited. Quoted headers (may contain internal commas). Exported via cfx5mondata.

"ACCUMULATED TIMESTEP","USER POINT,Mass Flow Monitor","USER POINT,Pressure Ratio"
1,-4.53497200e+01,2.13941860e+00

Flow360 Steady — Comma-delimited. physical_step (first column) is ignored, pseudo_step (second column) is X-axis.

physical_step, pseudo_step, CL, CD, ...
0, 0, -1.480, 12.750, ...
0, 10, -4.620, 42.375, ...

Flow360 Transient — Comma-delimited. physical_step (first column) is X-axis. Only the last row per step is used.

physical_step, pseudo_step, CL, CD, ...
0, 0, -2.418, 2.240, ...
0, 24, -2.418, 2.240, ...
1, 0, -2.418, 2.240, ...

Ansys Fluent — Space-delimited .out file. The line starting with ( is the header (everything above is comments).

"force-and-mom-file-0"
"Iteration" "fx-1-stabaxis etc.."
("Iteration" "fx-1-stabaxis" "fz-1-stabaxis" "my-1")
1 175342.7 220725.8 18475.2

SU2 — Comma-delimited. Time_Iter, Outer_Iter (first two columns) are ignored, Inner_Iter (third column) is X-axis.

"Time_Iter","Outer_Iter","Inner_Iter","rms[P]","rms[U]"
0,0,0,-4.953,-16.084
0,0,1,-5.073,-4.883

2. Layout

The application consists of three panels and a status bar.

+----------+----------+-------------------------------+
| File     | Variable | Chart                         |
| Panel    | Panel    |                               |
|          |          |  SMA Controls                 |
| File     | Variable |  ImPlot Chart                 |
| List     | Checks   |  (with convergence overlay)   |
|          |          +-------------------------------+
|          |          | Statistics Table              |
|          |          | (stats + clipboard copy)      |
+----------+----------+-------------------------------+
| Status Bar: Solver: Flow360 Steady | Path: ...      |
+-----------------------------------------------------+

• File Panel (left): List of loaded files. Click to select.
• Variable Panel (center): Variable checkboxes. All/None buttons for bulk selection.
• Chart Panel (right): Chart, convergence overlay, SMA controls, and statistics table.
• Status Bar (bottom): Displays the current solver and folder path.

Drag the dividers between panels to resize panel widths.

3. Loading Files

Open Folder

Select File > Open Folder to open a folder selection dialog. All supported files (.csv, .out) in the selected folder are loaded automatically.

Errors may occur if files with different solver formats share the same extension in the same folder.

Open Files

Select File > Open Files or click the Add Files button in the File Panel to open a file selection dialog. Multiple files can be selected at once.

• Supported filters: All Supported (.csv, .out), CSV Files (.csv), Fluent Output (.out)
• Duplicate files are not loaded.
• Files are automatically sorted by name.

Clear All

Select File > Clear All to remove all loaded files.

Auto Reload

Enable the Auto Reload checkbox at the top of the File Panel to poll loaded files every 2 seconds and reload any that have been modified.

• Useful for monitoring convergence in real time while the solver is still running.
• While Auto Reload is enabled, the chart's X-axis automatically follows the data to the latest point.

4. CFD Solver Selection

Select the appropriate solver from Settings > CFD Solver.

Changing the solver automatically reloads all loaded files with the new solver settings.

Legend Position

Change the chart legend position from Settings > Legend Position.

CFX Install Path

Select Settings > CFX Install Path to open a modal for configuring the CFX bin folder path.

• The current path is shown in an editable text field. You can type directly or use the Browse button to select a folder.
• The path should point to the folder containing cfx5mondata.exe (e.g., C:\Program Files\ANSYS Inc\v242\CFX\bin).
• Required for the Tools > Extract from CFX feature.

X-Axis Warning

If the X-axis values are not sequential (non-uniform step size) when data is loaded, a warning modal is displayed. This may indicate an incorrect solver selection for the data. Please verify the solver in Settings > CFD Solver.

5. Chart

Variable Selection

Check the variables to display in the Variable Panel.

• All: Select all variables
• None: Deselect all variables

Only checked variables are shown in the chart and statistics table.

SMA (Simple Moving Average)

Use the SMA controls at the top of the chart to configure moving averages.

• SMA-1 / SMA-2: Enable/disable each with checkboxes
• Set window size via the number input (min 2, max = number of data rows)
• SMA lines are drawn as thick lines over the raw data

Convergence Overlay

Convergence indicators for each variable are displayed in the top-right corner of the chart.

R-S1:0.05%  R-S2:0.10%  S1-S2:0.03% OK

Convergence symbols:

The same color thresholds are applied to variable names in the Variable Panel and file names in the File Panel. A file's name color reflects the worst convergence state among its variables (dark/light tones are chosen automatically based on the active theme).

Save Chart Image

Click the Save Image button next to the SMA controls to open a save dialog and write the chart area to a PNG file. The chart panel is captured at its current pixel size.

Chart Controls

The ImPlot chart supports mouse interaction:

• Drag: Pan the chart area
• Scroll: Zoom in/out
• Double-click: Reset chart range (fit)
• Right-click: Chart options menu

6. Statistics Table

Below the chart, statistics for selected variables are displayed in a table.

Clipboard Copy

Click the Copy button to copy statistics data in tab-separated format to the clipboard. This can be pasted directly into spreadsheets such as Excel.

Use the checkboxes next to the Copy button to select which columns to copy:

• SD / Mean / Final / S1 / S2 / Diff

7. Tools

Extract from CFX

Select Tools > Extract from CFX to extract USER POINT monitor data from a CFX result file (.res) to CSV.

1. CFX Install Path must be configured in Settings first.
2. Select a .res file.
3. Extraction runs in the background with a spinner indicator.
4. A result popup is shown on completion:
   • Success: {filename}_userpoints.csv is created in the same folder as the .res file and automatically loaded into the app.
   • Failure: An error message is displayed.

Internally, this calls ANSYS cfx5mondata.exe to perform the extraction.

8. Theme

Change the UI theme from the View menu.

• Dark (default)
• Light
• Classic

9. Settings Persistence

The following settings are automatically saved on exit and restored on next launch:

• CFD Solver selection
• Theme
• Last opened folder path
• SMA window sizes and enabled states
• Legend position
• CFX Install Path

Settings file location:

• Windows: %APPDATA%\CfdConvWatch\cfdconvwatch.ini
• Linux: $XDG_CONFIG_HOME/CfdConvWatch/cfdconvwatch.ini (falls back to ~/.config/CfdConvWatch/cfdconvwatch.ini)

The OS-standard per-user config location is used, so writes don't require elevated privileges and settings remain isolated per user account.

Trademarks

ANSYS, CFX, and Fluent are registered trademarks of ANSYS, Inc. Flow360 is a trademark of FlexCompute, Inc. SU2 was developed at Stanford University. This software is not affiliated with, endorsed by, or sponsored by any of these organizations.

License

Freeware - free for personal and commercial use. No warranty.

Copyright 2025 CLEW, Inc. https://www.clew.tech