An improved algebraic model for by-pass transition for calculation of transitional flow in pipe and parallel-plate channels

Abstract

Original scientific paper https://doi.org/10.2298/TSCI19S4123N Modified algebraic intermittency model developed by E. Dick and S. Kubacki was used to describe laminar-turbulent transition. In this work a modification of this model was made for simulating internal flows in pipes and parallel-plate channel. In particular, constants present in this model were modified. These modified constants are the same for different flows in pipes and parallel-plate channels. In this work, a dependence of friction factor on Reynolds number and turbulence intensity were determined as well as the localization of laminar breakdown and fully developed flow. Obtained results were compared with theoretical and experimental data presented in the literature.

Validation of Modified Algebraic Model during Transitional Flow in HVAC Duct

“…Extreme values of shear stress between the two models are different but the localisation of breakdown coincide. Shape of wall shear stress results from the modified k − ω model are sharpener due to the fact of the model formulation-it was also described in [20,26]. For k − omegaSST shape of wall shear stress is compatible with [29].…”

“…This model introduce factor γ which is a multiplier of the production term in the k-equation. As shown in [15,16,20,26] it enables more accurate description of the flow in the laminar, transitional, and turbulent range. The k and ω equations are defined:…”

“…Due to the slightly different flow characteristics in pipes, especially due to different pressure gradient, it was necessary to tune the model constants. As shown in [26], the following model constants shown in Table 1 are suitable for simulating flow in pipes, especially the inlet section where transition phenomena between laminar and turbulent flow occurs. Proposed model is applicable to transient simulations [15], however in terms of research conducted in this paper there is no need to perform time-accurate simulations.…”