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docs(changelog): record the changes since 0.4.0 #102

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100 changes: 100 additions & 0 deletions CHANGELOG.md
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Expand Up @@ -18,12 +18,112 @@ All notable changes to CableDyn are recorded in this file. The format follows
`n_fluid_nodes`, `fluid_node_positions` and `update_fluid_fields`. The field is sampled and held
as in the standalone march and in OpenFAST; in current and waves a stepped cable matches the
standalone driver to the digits of its output.
- `Line.section_curvature()` and the C API quantity `CD_C_LINE_SECTION_CURVATURE` return `CurvX`
and `CurvY` at every node of a finite-EI line in one evaluation.
- `CableDyn_GetInitNotes` in the C API and `CableDyn.init_notes` in Python: the notes of the last
deck initialisation on the point route and the aggregate, for a host that does not read the
standard streams.
- Python: `CableDyn.init_line`, `init_lines` and `calc_output_derivatives` bind the raw-array line
calls and the load Jacobians of the C API.
- Python: `read_output` reads both tables of `<root>.modes.out` into `NaturalModes` and
`ModeShapes`; `DriverResult` gains `modes_output` and `read_modes()`.
- Range graphs in coupled OpenFAST runs: the `LINES` `Outputs` flag `r` and `RangeStart` now write
`<RootName>.CD.Line<L>.range.out` in a single-turbine run, from the committed `dtM` steps of
`.CD.out`, once per step when OpenFAST retries a step, and across a checkpoint restart. A
turbine's own instance in FAST.Farm writes `<RootName>.T<n>.CD.Line<L>.range.out`. A FAST.Farm
shared mooring and the C API reject the flag by name.
- An OpenFAST initialisation note when the deepest interval of the SeaState depth grid exceeds 5 %
of the depth and a line lies in it: the field is linear there, unlike a deck depth table.
- An initialisation note names the lines that a current can move along a seabed without friction.
- `WaveKin 7`: each row of `wave_frequencies.txt` may carry its own `beta`, as MoorDyn-C reads it,
so that a component file can describe a short-crested sea; vessel RAOs take each row's heading.
- `WaveRefX` and `WaveRefY` options: the point that an elevation record or a component file
(`WaterKin WaveKinMod 1`, `WaveKin 3` and `7`) refers to. An extension of CableDyn; default 0, 0.
- CI: a Linux job runs the full test suite on the Prescott OpenBLAS kernel and fails on a fallback
note in any shipped example deck.

### Changed

- A standalone deck with `TMax 0` no longer needs `dtM`: the static check marches no step, so it
runs without one on every standalone route and writes the same `t = 0` row as with one. A
mixed deck that marches no step no longer prints the `dtM` advisory.
- Wave kinematics cost half to a fifth as much, depending on the compiler: on a 298-node line
in a 4,200 s elevation record of 2,400 components the sum falls from 6.0 to 3.0 ms per step
in the release build and from 18 to 3.6 ms in a GNU AVX2 build. Results change at round-off.
- `CableDyn_GetLineValues` evaluates the position, velocity, acceleration, tension, curvature,
bend moment, declination and azimuth of a line in one pass, without a text token per node. The
values are unchanged bit for bit. A read of `EI = 0` tension was O(n²) and is now linear.
- A coupled run restarts from a checkpoint at any glue step: `ChkptTime` need not be a multiple of
`dtM`, and the restarted run matches the uninterrupted one bit for bit.
- Range graphs are written when the host reports a completed run, so also at FAST.Farm's last
whole `DT_Low` and after `CalcSteady`. An earlier run's range graphs are removed as soon as the
deck is parsed, and a run that stops on an error writes none.
- The Python deck validator reads the files a deck names (WaterKin, the MoorDyn-C kinematics
files, motion and vessel records, the RAO table, bathymetry, Syrope) and refuses what the solver
refuses.
- A direction bin below the smallest normal weight holds no energy: its components are exactly
zero, and a vessel RAO table needs no heading for it.
- The C API refuses the flag `r` on `EI = 0` decks too, which it accepted without writing a file.

### Fixed

- Nodal curvature under a tapered bend stiffener: a node took the stiffness of the softer
neighbouring element, which steps at every node of a taper, and so overstated the curvature
by about `h |EI'| / (2 EI)`. It now takes the stiffness `EI(s)` at the node, and the softer
side only at a real step of the section (the bare tip, stiffener rows that do not match, two
line types).
- Element curvature under a tapered bend stiffener: the peaks of `.elements.out` and the node
values of `OutputRecovery element` read the element's interpolation, which bends under one
stiffness per element. Against the section its curvature is off by the same `h |EI'| / (2 EI)`,
high where the curvature falls toward the tip and low where it rises. On an element with a
sleeve they now report the section: the moment over `EI(s)`.
- Curvature and bend moment of a stretched finite-EI line: the node outputs read the conjugate of
the tangent as the moment, which put `Curv` 2 ε and `BendMom` ε below their definitions.
`Curv` is now the geometric curvature of the stretched line and `BendMom` the moment that
balances the forces, `EI κ / (1 + ε)`.
- An `EI = 0` line whose deck chord heads within 45 degrees of +X reported its azimuth in [0, 360)
instead of (-180, 180] outside the standalone `EI = 0` route: in the C API and Python, on the
standalone mixed and multibody routes, and in OpenFAST. Its `L<L>N<J>Azi` channels, the
`Azimuth` column of the static profile and the azimuth of the initialisation summary now follow
the documented range on every route.
- A solver step retry in OpenFAST works at any `dtM/DT` and matches an unretried step exactly,
including across a restart; it rebuilt the model at `dtM = DT` and stopped at `dtM > DT`.
- `CalcSteady` with several operating points no longer stops at the second, works at `dtM` larger
than `DT`, and `.CD.out` and the range graphs run to the end of its run. `-VTKLin` works at `dtM`
larger than `DT`. Linearisation after `CalcSteady` or after a restart keeps its line states.
- A restart before the first commit keeps a body or rod at its start, and a restart no longer
rewrites `.CD.static.out`.
- Every initialisation note of a coupled line reaches the console; long lists were cut or dropped.
- The OpenFAST module driver runs a rotating motion in a single-precision build.
- A range-graph file that cannot be written completely is removed instead of left behind.
- The C API messages of `CableDyn_UpdatePointFluidFields` and `CableDyn_CalcOutputDerivatives` on
the coupled aggregate name its real scope: decks with finite-EI lines, bodies or rods.

### Upgrading

- `Curv`, `CurvX`, `CurvY`, `BendMom` and `StfMom`, and the `Curvature` and `BendMoment` of the
static profile and the range graphs, change at nodes inside a bend stiffener. Curvature and
`BendMom` fall by that first-order error, on `lazy_wave_bend_stiffener.dat` by about 5 % on
0.2 m elements, 4 % on 0.15 m, 2 % on 0.1 m and 0.7 % on 0.05 m; `StfMom` rises by the same
moment, so the two still add up to the section moment. A line end on a conical root
changes likewise, and a step between rows on a taper now compares the two stiffnesses at the
node. Positions, forces, the section moment and every node outside a stiffener are unchanged.
- `PeakCurvature`, `BendMomentAtPeak` and `PeakXi` of `.elements.out`, so `bend_check` and
`element_range_graph` on that table, change on elements with a stiffener sleeve, and so do
`Curv`, `CurvX` and `CurvY` under `OutputRecovery element` at their nodes, where they now equal
the default recovery. The peaks fall by 1.6 / 3.1 / 5.8 % on 0.05 / 0.1 / 0.2 m elements of a
hang-off whose curvature falls toward the tip, and rise by up to 4.4 % on the 0.15 m elements of
`lazy_wave_bend_stiffener.dat`, whose curvature rises. Elements without a sleeve are unchanged,
and `CD_HermiteCable_Dyn_Curvature_Exact` stays the geometric trace.
- `Curv`, `CurvX`, `CurvY`, `BendMom` and `StfMom`, and the `Curvature` and `BendMoment` of the
static profile and the range graphs, rise on every finite-EI line: curvature by twice the axial
strain, the moments by the strain, at most 0.024 % and 0.012 % on the examples. `BendMom` equals
`EI × Curv` only to within the strain. Tension, positions and forces are unchanged, and so are
`OutputRecovery element` values on elements without a stiffener sleeve.
- Azimuth values of the `EI = 0` lines named above read 360 degrees lower on those routes.
- OpenFAST checkpoints change format: they carry the range graphs and the input of the last
commit, so a checkpoint written by an earlier CableDyn cannot be restarted with this one.

## [0.4.0] - 2026-11-04

### Added
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