Application of Low-Reynolds Number Based k-ε Turbulence Models for Separated Flows: Model Validation and Assessment

ABSTRACT

A finite-volume based 2-D axisymmetric k−ε turbulence models have been developed to study the phenomena of fluid flow and heat transfer in separated, re-attached and re-developed flows. These turbulence models are based on the concept of low-Reynolds number flows using wall damping functions, as contrast to standard k-ε turbulence model using the law-of-wall. Two different sets of wall damping functions used in the present models are based on Launder and Sharma [1] and Goldberg et al. [2]. It should be noted here that the low-Reynolds number based turbulence models are applicable for developing flows with rigid and/or flexible wall boundaries as well as fully developed flows. Subsequently, the developed models are validated by comparing the predicted fluid flow and heat transfer quantities with the measured data against two benchmark problems; one is fully turbulent flow in a uniform pipe and another is turbulent flow and heat transfer in a pipe with sudden expansion in cross-section, a case of flow separation, re-attachment and re-development. Finally, the models are assessed in terms of the solution accuracy as well as the computational and simulation times required by each of these models. The overall observations from the above model validation and assessment study are presented.

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