
ID	0122
Class	DOCUMENTATION
Severity	1
Status	blocked

Models: — (annotated on the fhsim_environment library group)

Found: 2026-10-20, hydrodynamics overview section 7 (doc/hydrodynamics-overview.md in fhsim_workspace), feature m2-hydro-doc-gaps

Decision needed: Owner: for each unsourced coefficient below, keep it and document it as a calibration or engineering default, or replace it with a sourced value (which moves results)? Who checks the DNV-RP-C205 tables and Ersdal-Faltinsen 2006 against the originals?

Evidence

Coefficients with no source, or a source that was not checked, in include/fhsim_environment/hydrodynamics/:

CylinderHydro.h:79-80: the second and third Cd branches are "the original fit of unknown source".
CylinderHydro.h:97: Ct has "no literature reference".
CylinderHydro.h:74: White eq. (3-225) is "cited from memory, not checked against the book".
CylinderHydro.h:307-308, 325: every DNV-RP-C205 table (Table A-1 and the Morison inertia text) is "not checked here".
Ersdal-Faltinsen 2006 (EF2006) is cited without a full reference and unchecked (doc/user/hydrodynamics.md:39).
TwineCrossFlow.h:81-82: ct = 0.01 and cnKnots = 0.4 are only "the 3.2.1 values".
DiskHydro.h:44-45: disc cdNormal = 1.2, cdTangential = 0.005; SphereHydro.h:44: sphere cd = 0.5. No source.

The matching items in fhsim_marine_elements are in MARE-0404.

Effect

The load level of cables, twines, discs and spheres rests on values nobody can trace. Users cannot tell calibrated values from placeholders.

Possible fix

No code change is needed to document: add a "source / status" column to the coefficient tables in doc/user/hydrodynamics.md. To replace a value, check it against the book or paper first; each replacement moves a baseline and needs a ruling (doc/agents/baselines.md).

Test that would prove it

For each replaced value, a test against the digitised source data (the pattern of tests/data/*_digitised.csv).

Risk

Documenting is risk free. Replacing moves baselines.