A D3Q7 passive scalar rides on the D3Q19 flow: it is advected by the
cell velocity, diffuses with the fluid's thermal diffusivity (the
relaxation time follows from k / (rho c)), and feeds back into the
momentum through a per-cell Boussinesq force when the domain has an
expansion coefficient and gravity. Walls and obstacle faces hold a
temperature (anti-bounce-back), a heat flux (added to the bounced
population) or are adiabatic (bounce-back); velocity inlets carry the
held temperature in, pressure outlets copy their neighbour.
The heat crossing each face group is accumulated during streaming and
reported in physical units (W) in the result's heat histories, next to
the force histories; frames gain a temperature field and the stats
report the thermal relaxation time.
Closed-form checks: linear conduction between held plates, a flux wall
against q H / k with the wall's heat balance, an inlet temperature
carried through a plug flow, and a periodic blob that conserves its
total and returns after one lap. The de Vahl Davis cavity (Ra 1e3 and
1e4 against the published Nusselt numbers) is there as an ignored test
because it takes minutes.
The GPU backend declines domains with heat for now and asks for the
CPU; its kernels follow.
Part of #157.
Crates fieldcraft-*, binaries fieldcraft and fieldcraft-cli, the .fieldcraft file (format tag
fieldcraft/1, manifest fieldcraft.json), FIELDCRAFT_* environment variables, the MCP server
name, egui widget ids (fc_*), the app icon document FieldCraft.icon and its generated family,
docs and licences. No compatibility shim: no files of the earlier name exist.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm
Model: Newtonian fluid materials; fluid domains (box, spacing, conditions on
the box faces, obstacle bodies with conditions on their named faces, initial
velocity, body acceleration); fluid steps with caps. Deck writers refuse
fluid steps; a fluid-only model needs no mesh in model.check; one step
selector (Model::select_step) for every solver.
New L2 crate modelcraft-lbm: D3Q19 two-relaxation-time collision with Guo
forcing; halfway bounce-back walls (moving walls after Ladd), slip faces,
periodic pairs; Zou–He velocity and pressure faces with the D3Q19
transverse correction; obstacles voxelised from the face-tagged boundary
surface with exact predicates and symbolic perturbation; momentum-exchange
forces per box face and per B-rep face; unit conversion, automatic time step
and Mach/tau limits; bounded runs with frames and force histories.
Engine: model.fluid_domain.create/edit/delete, model.fluid_domain.boundary,
solve.fluid (obstacles from the open design or imported surfaces, lowerable
caps), solve.probe for fluid fields and wall force histories. Fluid Domain,
Inlet & Outlet and Lattice Boltzmann toolbar entries are ready.
Verification (analytic): plane Poiseuille exact with Λ = 3/16 and second
order (2.000) with Λ = 1/4; Couette exact with the wall shear; Taylor–Green
decay second order (2.01, 2.00); staircase pipe; Stokes drag of a sphere
array within 1.7% of Hasimoto at R = 6; Zou–He channel; mass conserved to
round-off; bit-for-bit reproducibility. Benchmark: Schäfer–Turek 2D-1.
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm
Co-authored-by: jyviko <2501648+jyviko@users.noreply.github.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Christian Svensson