All the simulations presented in this paper are performed using
the FLUENT code [25] on an Intel CoreTM2 Duo Processor 2.2GHz
PC. The convergence criteria for all of the governing equations are
set such that summation of the relative residual in every control
volume is less than 105. The decay trend in the residual plot for
each equation is also considered as an alternative criterion. In
addition, according to the ASMS V&V 20-2009 [26], the numerical
error of the present computation has been estimated using socalled
a five-step procedure. Considering the fully- developed Nu
number for Rein ¼ 40,000, the numerical error for this predicted
parameter is about 0.16% that is estimated based on the factor of
safety (Fs) ¼ 1.25 and the expansion factor (k) ¼ 1.15.