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Computational Investigation into Buoyancy-Aided Turbulent Flow and Heat Transfer to Air in a Vertical Tube

W. S. Kim
School of Engineering and Physical Sciences, University of Aberdeen, Aberdeen AB24 3UE, UK

J. D. Jackson
School of Mechanical, Aerospace and Civil Engineering, University of Manchester, Manchester M1 3 9PL, UK

S. He
School of Engineering and Physical Sciences, University of Aberdeen, Aberdeen AB24 3UE, UK

The study reported in this paper is concerned with the modelling of turbulent mixed convection to air flowing upwards through a uniformly heated vertical tube. Although considerable work has been done on this topic by experimentalists, it is not easy to separate the individual effect on turbulence of buoyancy, non-uniformity of fluid properties and flow acceleration as these are often complicatedly coupled and can either be additive or in opposition to each other in a particular flow condition. Recently, interesting DNS simulations of mixed convection have been reported for conditions of constant properties with buoyancy accounted for using the Boussinesq approximation. This has interestingly isolated the influences of buoyancy from other effects. The objective of the current study is to simulate these DNS data using some most recently developed eddy viscosity turbulence models as well as some 'classical' ones so as to assess their ability in reproducing the buoyancy-effects under such an idealized situation and more importantly to develop an understanding of the underlining reasons for the largely diverse performance of the various models in simulating buoyancy-influenced flows and therefore shed some light on future improvements for turbulence models.

pages 519-522

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