A correct choice of under-relaxation factors α is essential for costeffective
simulations. Too large a value of α may lead to oscillatory or even
divergent iterative solutions, and a value which is too small will cause
extremely slow convergence. Unfortunately, the optimum values of underrelaxation
factors are flow dependent and must be sought on a case-by-case
basis. The use of under-relaxation will be discussed further in Chapters 7
and