nx_heat_conduction2d.nx

nx_heat_conduction2d.nx -- FOOD-SCIENCE SUITE / NUMERICAL HEAT TRANSFER. A real 2-D transient conduction solver (explicit finite difference) for the retort cold spot: a square of food, surface held at the retort temperature, interior starting cold, relaxing over time. This steps the suite from analytical (Biot/Fourier) toward numerical simulation -- the honest 3-D CFD gap shrinks from "nothing" to "2-D transient". INTEGER-EXACT by design: at the explicit-stability limit (mesh Fourier number Fo = 1/4) the 2-D update is EXACTLY the average of the four neighbours -- T_new[i,j] = (T[up]+T[dn]+T[lf]+T[rt]) / 4 -- so no float and no stability blow-up. Dirichlet boundary (surface temp) fixed; interior relaxes toward it; the centre is the cold spot. THE exceed vs the field: not depth over COMSOL, but a sovereign, integer-deterministic transient field solve that composes with the preservation cook (once the cold spot reaches the lethal temperature the 12-D clock can start) -- no license, bit-reproducible. grounded: explicit_finite_difference_heat_equation + fo_quarter_stability genealogy_id: numerical_heat_transfer + nishi_food_science_suite