ReadonlyexternalEnclosed outer area, consistent with pi * outerDiameter^2 / 4, with area units.
ReadonlyinternalInternal flow area, consistent with pi * internalDiameter^2 / 4, with area units.
ReadonlyinternalActual internal diameter, with length units.
ReadonlymaterialPipe wall area, equal to external minus internal cross-sectional area.
ReadonlyouterExternal diameter, with length units; greater than the internal diameter.
ReadonlywallWall thickness, equal to half the difference between outer and internal diameters.
Structural geometry contract for a uniform circular pipe cross-section. Implementations must supply finite, positive, mutually consistent dimensions and areas. Length, roughness, placement and operating state belong to the application.