LinearEuler3D: heterogeneous sound speed + impedance-matched Riemann flux#138
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…flux Bring the 3-D linear Euler model up to parity with LinearEuler2D: - Carry the sound speed as solution variable 6 (nvar 5 -> 6), static in time (zero flux/source), so heterogeneous media are supported. The scalar attribute `c` remains as the reference value used by initial conditions (SphericalSoundWave fills variable 6 with it). - Replace the local Lax-Friedrichs Riemann solver with the impedance-matched (characteristic/Godunov) flux used by the 2-D model: interface states resolved with the one-sided impedances Z = rho0*c, so material interfaces in a heterogeneous c field get the physically correct transmission/reflection. - GPU backend: fluxmethod reads the per-node c (variable 6) and the boundaryflux kernel implements the impedance-matched flux; both drop the scalar `c` argument (signatures now mirror the 2-D kernels). The radiation BC kernel now takes the interior boundary state and copies c through to extBoundary so face Riemann solves see a consistent sound speed, with the acoustic perturbation still zeroed. - Register a CPU radiation BC in AdditionalInit_LinearEuler3D_t (previously the radiation BC existed only in the GPU backend); the GPU AdditionalInit calls the parent and overwrites it with the kernel wrapper, mirroring the 2-D module structure. - Fix the entropy function: s(3)*(3) typo -> s(3)*s(3), include the w contribution correctly, and use the per-node sound speed. - Update the model documentation accordingly. Motivation: 3-D ultrasound computed tomography forward modeling (SELF-UCT AcousticTomography3D) needs spatially varying sound speed with impedance-matched interface handling, exactly as the 2-D class has. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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…139) * LinearEuler 2D/3D: variable background density via static nodal rho0 Promote the background density rho0 from a scalar model attribute to a static per-node solution variable, mirroring the heterogeneous sound-speed pattern from #138. This lets rho0 vary in space (e.g. across material interfaces) alongside c, so heterogeneous media with both density and sound-speed contrast are supported. - 2D: nvar 5->6 (rho0 = variable 6), nstepped stays 4. - 3D: nvar 6->7 (rho0 = variable 7); set nstepped=5 (previously unset, relying only on zero flux/source to hold the auxiliary fields static). - Interior flux, entropy_func, and the impedance-matched Riemann flux now read per-node rho0. The Riemann solver uses per-side impedance Z = rho0*c, so material interfaces (density and/or sound-speed jumps) get the physically correct reflection/transmission; the reconstructed density/momentum/pressure fluxes use the face-averaged rho0 and c^2 (the same pragmatic treatment already used for c^2). The scalar rho0 attribute is retained as the reference value that fills the field in the built-in initial conditions. - GPU: fluxmethod/boundaryflux kernels read per-node rho0 and drop the scalar rho0 argument; BC kernels copy rho0 through to the exterior state (signatures now mirror the c handling in #138). - Entropy stability: for piecewise-constant material regions aligned with element boundaries, element interiors have grad(rho0)=grad(c)=0 (so the flux-divergence form is exact) and the impedance-matched Riemann flux carries the entropy-stable interface dissipation. Also in this change: - Add a CPU radiation BC to the 2D model (previously only the GPU backend registered one); it zeros the acoustic perturbation and copies c and rho0, mirroring the 3D model. Register it in AdditionalInit_LinearEuler2D_t. - Add a PML entropy_func override so the PML variant keeps using its scalar rho0 (its variable 6 is the auxiliary phi_rho, not rho0). - Fix the 2D entropy_func s(3)*(3) typo (already fixed for 3D in #138). - boneandmarrow example: stamp a per-material rho0 (muscle/bone/marrow) alongside c, exercising a genuinely heterogeneous impedance field. - planewave examples: set the new rho0 variable in the initial condition and the prescribed boundary state. - Update the 2D/3D model docs. CPU (gfortran) build is clean and all 7 LinearEuler ctests pass; boneandmarrow entropy is finite and monotonically decreasing. GPU kernels to be validated by CI. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com> * docs: fix LinearEuler doc staleness after variable-density change - 2D model: the base LinearEuler2D_t now registers a CPU radiation handler (not GPU-only), so update the BC section accordingly. - 3D model: remove two dead example links (spherical_soundwave_closeddomain and planewave_propagation examples do not exist); keep the radiation example, which is the only 3D example present. - PML model: document the new entropy_func override and clarify that the PML variant keeps rho0 as a scalar (its slot 6 is phi_rho, whereas the parent model now carries rho0 as a per-node solution variable). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com> --------- Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Summary
Brings the 3-D linear Euler model up to parity with
LinearEuler2Dso it can support heterogeneous media (the driver is 3-D ultrasound-computed-tomography forward modeling in SELF-UCT):nvar5 → 6), static in time (zero flux, zero source), mirroring the 2-D convention. The scalar attributecremains as the reference value used by initial conditions (SphericalSoundWavefills variable 6 with it).riemannflux2d_LinearEuler2D_t: interface states resolved with the one-sided impedancesZ = rho0*c, giving physically correct transmission/reflection at material interfaces in a heterogeneouscfield.fluxmethodreads the per-nodec; theboundaryfluxkernel implements the impedance-matched flux; both drop the scalarcargument (signatures now mirror the 2-D kernels). The radiation-BC kernel now takes the interior boundary state and copiescthrough toextBoundary(acoustic perturbation still zeroed) so face Riemann solves see a consistent sound speed.AdditionalInit_LinearEuler3D_t(previously radiation existed only in the GPU backend); the GPUAdditionalInitcalls the parent and overwrites the registration with the kernel wrapper, mirroring the 2-D module structure.s(3)*(3)typo →s(3)*s(3), and the internal-energy term now uses the per-node sound speed.docs/Models/linear-euler-3d-model.md).Breaking change
LinearEuler3Dgrows from 5 to 6 solution variables and the GPU kernel signatures forfluxmethod_LinearEuler3D_gpu/boundaryflux_LinearEuler3D_gpu/hbc3d_radiation_lineareuler3d_gpuchange. Downstream code that sets initial conditions directly must fill variable 6 with the sound speed.examples/linear_euler3d_spherical_soundwave_radiation.f90needs no changes (it goes throughSphericalSoundWave).Testing
selfish:latest-x86-cuda130-sm103toolchain container compiles and installs clean, including the 3-D example.AcousticTomography3D) builds and links against this branch's install.fprettify --config-file ./fprettify.config --case 1 1 1 1reports no diffs on the touched files.🤖 Generated with Claude Code