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The five things most likely to trip you up

The five things most likely to trip you up

Stated in .claude/rules/physics-numerics.md; derived here.

  1. The wall function is 1 − exp(−6.2(d + 0.01)): plus, and 6.2 nm⁻¹ (ESI 0.62e1). → knowledge/01-physics-epnpns/08-errata-in-the-source-with-the-arithmetic.md.
  2. The steric flux sign: β_i enters the bracket with +, and the bracket is negated. → knowledge/01-physics-epnpns/02-governing-equations.md#22-size-modified-nernstplanck.
  3. No dielectric-gradient body force in the published model (f = ρ_ion E only); adding one is a deviation. → knowledge/01-physics-epnpns/02-governing-equations.md#23-navierstokes-variable-density-and-viscosity.
  4. Einstein holds only at infinite dilution: D_i/μ_i drifts to 1.2–1.7 × kT/e between 0.15 and 3 M, so Poisson–Boltzmann is a distinct model, not PNP at V = 0. → knowledge/02-electrokinetics-background/index.md.
  5. 1/r terms return NaN at integration order 2. → knowledge/06-numerics-fem/02-axisymmetric-weak-forms.md#22-quadrature-verified-experimentally.