The discretised equations at each nodal point represent a set of algebraic
equations that needs to be solved. Normally iterative numerical techniques
are used to solve large equation sets. These methods start the solution
process from a guessed distribution of the variable φ and perform successive
updates until a converged solution is obtained. Scarborough (1958) has
shown that a sufficient condition for a convergent iterative method
can be expressed in terms of the values of the coefficients of the discretised