Inspection of flow Inside Constant and sudden expansion cross-sections using new calibrated transitional SST model

Simulation of all flow regimes, including laminar, transition and turbulent using a unique model is the most important challenge in computational fluid dynamics. Furthermore, the existence of the transition phenomenon redoubles the challenge. In the present study, to simulate all internal flow regimes, the implementations of suitable values for tunable coefficients of the transitional SST model are investigated. 2-D and 3-D simulations are performed for Reynolds number from 1.4103 to 6.4×104 to evaluate the capabilities of the newly implemented coefficients. Three different test cases are used, including an axisymmetric pipe, the backward-facing step and a 3-D duct. Average velocity, friction coefficient and reattachment length compare against the experimental data. The results show, there are some deficiencies to simulate all internal flow regimes using the original transitional SST model. However, the newly implemented coefficients could predict characteristics of all internal flow regimes with acceptable accuracy in comparison to the experiments. The maximum error percentages for duct and step flows obtained 4.3 and 37 using the new coefficients, respectively, which were better than the previous models.

Keywords:

Transition , Internal Flow , RANS , Numerical Simulation