openfoam-31-solver-log-residual-format

name	openfoam-31-solver-log-residual-format
description	Sub-skill of openfoam: 3.1 Solver Log Residual Format (+5).
version	1.0.0
category	engineering
type	reference
scripts_exempt	true

3.1 Solver Log Residual Format (+5)

3.1 Solver Log Residual Format

Each iteration produces lines in this format:

smoothSolver:  Solving for Ux, Initial residual = 0.0118755, Final residual = 0.000302581, No Iterations 1
GAMG:  Solving for p, Initial residual = 0.150883, Final residual = 0.00896498, No Iterations 3

Regex for extraction:

import re
pattern = r'^(\w+):\s+Solving for (\w+), Initial residual = ([0-9.e+-]+), Final residual = ([0-9.e+-]+), No Iterations (\d+)'
# Groups: solver_name, field_name, initial_residual, final_residual, iterations

Time step markers:

Time = 150                    # steady: iteration number
Time = 0.0345                 # transient: physical time

Courant number (transient only):

Courant Number mean: 0.123 max: 0.987

Continuity errors:

time step continuity errors : sum local = 1.23e-07, global = -2.34e-15, cumulative = -5.67e-14

Convergence marker (SIMPLE):

SIMPLE solution converged in 285 iterations

End marker: End

3.2 foamLog Utility

foamLog log.simpleFoam
# Creates logs/ directory with per-field residual files:
#   logs/p_0          — initial residual for p
#   logs/Ux_0         — initial residual for Ux
#   logs/k_0          — initial residual for k
#   logs/contLocal_0  — local continuity error
#   logs/contGlobal_0 — global continuity error
# Format: two columns (iteration, value)

3.3 Python Log Parsing

import re
from pathlib import Path

def parse_openfoam_log(log_path):
    """Parse OpenFOAM solver log and extract residuals per field."""
    residuals = {}
    time_step = 0
    pattern = re.compile(
        r'(\w+):\s+Solving for (\w+), '
        r'Initial residual = ([0-9.e+-]+), '
        r'Final residual = ([0-9.e+-]+), '
        r'No Iterations (\d+)'
    )
    time_pattern = re.compile(r'^Time = ([0-9.e+-]+)')

    for line in Path(log_path).read_text().splitlines():
        time_match = time_pattern.match(line)
        if time_match:
            time_step = float(time_match.group(1))
            continue
        match = pattern.search(line)
        if match:
            field = match.group(2)
            if field not in residuals:
                residuals[field] = []
            residuals[field].append({
                'time': time_step,
                'initial': float(match.group(3)),
                'final': float(match.group(4)),
                'iterations': int(match.group(5)),
            })
    return residuals

3.4 postProcessing/ Directory

Function objects write to postProcessing/<name>/<startTime>/:

Function Object	Output File	Content
yPlus	yPlus/0/yPlus.dat	Wall y+ values
solverInfo	solverInfo/0/solverInfo.dat	Residuals per timestep
forceCoeffs	forceCoeffs/0/coefficient.dat	Cd, Cl, Cm vs time
probes	probes/0/p, probes/0/U	Field values at probe points
fieldMinMax	fieldMinMax/0/fieldMinMax.dat	Min/max per field

3.5 checkMesh Output

Key lines to parse:

Max aspect ratio = 5.08 OK.
Mesh non-orthogonality Max: 45.2 average: 12.3
Max skewness = 0.127 OK.
Min volume = 4.2e-11. Max volume = 1.68e-09.
Mesh OK.                                    # or: Failed N mesh checks.

3.6 Exit Codes

Code	Meaning
0	Success (End printed)
1	FOAM FATAL ERROR or FOAM FATAL IO ERROR
134	SIGABRT — assertion failure
136	SIGFPE — floating point exception
139	SIGSEGV — memory / corrupted mesh
137	SIGKILL — out of memory (OOM killer)
255	MPI error / decomposition mismatch

---