Module fluids 

Structs

AccelerationVector

Acceleration vector (m/s²). Return type of momentum-equation RHS evaluators.

BodyForceDensity

Body force per unit volume (N/m³).

CauchyStress

Cauchy stress tensor (Pa). Symmetric, positive-in-tension sign convention.

Density

Density (kg/m^3).

KinematicViscosity

Kinematic Viscosity (m^2/s). Equals dynamic viscosity divided by density.

Pressure

Pressure (Pascals).

ReynoldsStress

Reynolds stress tensor R_ij = ⟨u'_i u'_j⟩ (Pa, after multiplication by ρ in caller; here a kinematic Reynolds stress in m²/s² is also acceptable). Symmetric. Diagonal entries are non-negative (variances) — not enforced by the newtype to keep the constructor cheap; callers passing a tensor that violates the diagonal-positivity property are responsible for downstream interpretation.

RotationRateTensor

Rate-of-rotation (spin) tensor Ω = 0.5·(∇u − ∇uᵀ). Antisymmetric: Ω_ji = −Ω_ij, with Ω_ii = 0. new checks the antisymmetry invariant by exact equality.

SpecificEnthalpy

Specific Enthalpy (J/kg). Reference-state dependent; may be negative.

StrainRateTensor

Strain-rate tensor S = 0.5·(∇u + ∇uᵀ). Symmetric: S_ij = S_ji. new checks the symmetry invariant by exact equality, matching what natural construction 0.5·(G + Gᵀ) produces in IEEE 754. Use new_unchecked to bypass the check in hot kernels where symmetry is guaranteed by the algebra.

Velocity3

Fluid velocity vector (m/s).

VelocityGradient

Velocity gradient tensor ∇u. Pinned to the Jacobian convention: value[i][j] = ∂u_i / ∂x_j. Construction-time check is finiteness only — any finite 3×3 matrix is a valid velocity gradient.

Viscosity

Dynamic Viscosity (Pa·s).

ViscousStress

Viscous (deviatoric) stress tensor τ (Pa). Symmetric. Distinct from the full Cauchy stress σ = −p I + τ — only the viscous part appears in the dissipation Φ = τ:∇u ≥ 0 and entropy-production guarantees.

VorticityVector

Vorticity vector ω = ∇ × u (1/s). Pseudovector under spatial reflection.

WallShearStress

Wall Shear Stress magnitude (Pa). Stored as magnitude; sign convention is carried by the calling context, not by this type.