README

@Kim Jae Sik https://github.com/oathis/2DFluentPODGalerkin

Overview

This repository provides a pipeline that builds a Proper Orthogonal Decomposition (POD) Galerkin reduced-order model from 2D flow snapshots exported from Ansys Fluent. Given a target Reynolds number, the reduced model is solved to reconstruct the full flow field.

Requirements

• Python 3.9+
• Scientific Python stack (NumPy, Pandas, SciPy, Matplotlib, etc.)

Key Components

• PreProcessing/preprocessing.py: Sorts Fluent CSV snapshots by coordinates and generates _sorted files in batch.
• Galerkin_offline.py: Extracts the interior grid from the sorted snapshots, computes POD modes, pre-computes Galerkin tensors, and stores them in rom_offline_data.npz.
• Galerkin_online.py: Loads the offline data, solves the nonlinear equations for a specified Reynolds number, and exports the reconstructed pressure/velocity fields as CSV files and interpolated plots.
• PostProcessing/CalculateL2.py: Calculates the relative L2 error between the reference solution and ROM solution, and visualizes the error trend versus Reynolds number.

Usage

1. Data sorting
   Place Fluent case*.csv files in a working folder such as TrainData/ and run python PreProcessing/preprocessing.py to generate the _sorted files.
2. Offline stage
   Run PPE_POD_Galerkin_OFFLINE.py to read TrainData/case*_sorted.csv, compute POD modes and Galerkin tensors, and store the results in rom_offline_data.npz.
3. Online stage
   Run PPE_POD_Galerkin_ONLINE.py, enter the desired Reynolds number, and the reduced model will reconstruct the flow field, saving the output to FinalResult/rom_solution_Re_<Re>.csv along with PNG plots.
4. (Optional) Post-processing
   Run python PostProcessing/CalculateL2.py to compare the reference and ROM solutions and generate the Reynolds-number-dependent relative L2 error plot.

Outputs

• rom_offline_data.npz: POD modes, boundary conditions, and precomputed Galerkin coefficient tensors from the offline stage.
• FinalResult/rom_solution_Re_*.csv and plots: Reconstructed pressure/velocity fields from the online stage.
• rom_error_vs_re.png: Relative ROM error versus Reynolds number produced by the post-processing script.

https://github.com/oathis/2DFluentPODGalerkin