Numerical simulations of forced convection across a single tube to evaluate applicability of the DNS, LES and RSM methods

Forced convection across a single tube was investigated numerically for various Reynolds numbers using various numerical models to identify suitable ranges for each model. Direct numerical simulations (DNS), large eddy simulations (LES), and a Reynolds averaged model using the Reynolds stress model (RSM) were compared with experimental date. The calculations used unsteady two-dimensional models with air as the working fluid. For the mesh used here, for Re < 10,000, the DNS method gave good results. For 10,000 < Re < 100,000, the LES is preferred while for Re > 100,000, the RSM is better. Nonlinear phenomena were found for various Reynolds numbers. For Re < 100, the average Nusselt number did not change with time while for 100 ≤ Re < 1000, the average Nusselt number oscillated with time. The local Nusselt numbers along the entire tube are also discussed.