Multi-fluid Solver — Tier-1 Fluid Layer Validation

Resolve a fluid and flash it at (P, T). The fluid layer returns the equilibrium phase, vapor fraction (quality), density and viscosity. Try waterat 1.01325 bar / 298.15 K (liquid, ρ ≈ 997) and at 500 K (vapor).

March an optionally-heated pipe segment-by-segment from the inlet state, detecting phase change along the length. The default case (water, L=20 m, D=0.05 m, ṁ=0.05 kg/s, q=5000 W/m, T_in=370 K) boils the stream and reaches outlet quality ≈ 0.85. For a genuine two-phase inlet set an inlet quality; an inclination drives the two-phase ρ_insitu·g·sin θ static head — try the vertical wet-steam riser preset.

The same 1e-10-validated head-based GGA, now solving an incompressible non-Newtonian network — no new solver. A fixed looped branch network is solved twice: as water (Newtonian) and as a Bingham slurry with a yield stress. The friction viscosity is routed through a RheologyFluidProvider (μ_app(γ̇) = τ_y/γ̇ + μ_p). The yield stress raises the pressure gradient and shifts the flow split.

Register case A8 is closed: a compressible nitrogen + TCV net now routes to the marching engine (not the incompressible GGA). The valve is modelled as an IEC 60534-2-1 gas throttle (real-gas EOS density, x_T choke factor, Y expansion factor). Isenthalpic Joule-Thomson cooling is applied across the valve — T_out drops from T_in(real-gas JT coefficient). The valve chokes when x ≥ F_γ·x_T — critical flow, independent of downstream pressure, with Y pinned at 2⁄3 (IEC 60534 choked branch). Oracle: test_solve_valve_marching.