Predication of Laminarizations in Buoyant Turbulent Pipe Flow of Low Prandtl Number Fluid

Abstract

Turbulent pipe flow with Pr = 0:026 is studied using Reynolds Averaged Navier Stokes (RANS) and Large Eddy Simulations (LES) for Red = 5300 under various Richardson numbers with a constant heat flux boundary condition. The goal of this study is to better understand and improve predictions of buoyancy aided mixed convection in low Prandtl number fluids with an emphasis on the transition to laminarization.

The present work is validated using Direct Numerical Simulations (DNS) data and LES data available in literature and also performed in-house. At the onset of this investigation very limited data existed for only a few Richardson numbers in peer reviewed literature. Using this data as a validation, LES was performed using OpenFOAM to fill in gaps and widen knowledge in the ranges of interest. Using this newly created data set, a thorough investigation is performed to determine how common eddy-viscosity RANS models predict mixed convection turbulent pipe flow in low Prandtl number fluids. Using this for a base of knowledge, a thorough calibration framework is constructed that allows for the calibration of low Reynolds k − ε turbulence models. Additionally, to assess the improvement of model performance a quantitative comparative error analysis framework is developed to guide in model calibration. The results from this study represent a solid foundation for future model development that is easily accessible for the user.