Boundary Condition Designation.

The type of boundary conditions present are designated by numerals 0, 1, 2, 3, 4, and 5. Types 4 and 5 are less common, used primarily for the Heat Equation in the 1-D rectangular coordinate system. The zeroth type of boundary occurs where there is no physical boundary present. For example, a semi-infinite body with a fixed temperature at x = 0 has number designation X10. Similarly, the 2-D quarter-infinite body with type 1 boundaries at x = 0 and y = 0 is X10Y10. Finally, the zeroth type of boundary also occurs at the center of a solid cylinder or a solid sphere. For example, a solid cylinder with a prescribed surface heat flux has designation R02.