Design of a Direct numerical Simulation of flow and heat transfer in a T-junction

Design of a Direct numerical Simulation of flow and heat transfer in a T-junction

Ajay Kumar, Aniketh (NRG (Nuclear Research and Consultancy Group) Petten)
Mathur, Akshat (NRG (Nuclear Research and Consultancy Group) Petten)
Gerritsma, M.I. (TU Delft Aerodynamics)
Komen, Ed (NRG (Nuclear Research and Consultancy Group) Petten)

2023

Several investigations have been undertaken to study the velocity and temperature fields associated with the thermal mixing between fluids, and resulting thermal striping in a T-junction. However, the available experimental databases are not sufficient to describe the involved physics in adequate detail, and, due to experimental limitations, accurate data on velocity and temperature fluctuations in regions close to the wall are not available. Computational Fluid Dynamics (CFD) can play an important role in predicting such complex flow features. However, predicting complex thermal fatigue phenomena is a challenge for the available momentum and heat flux turbulence models. Furthermore, such models need to be extensively validated. The aim of the present work is to design a reference numerical experiment for Direct Numerical Simulation (DNS) of a thermal fatigue scenario using Reynolds-Averaged Navier-Stokes (RANS) simulations. First, the feasibility of scaling down the Reynolds number from experimental cases to a computationally-feasible range is investigated. The junction corner shape is also modified to a slightly rounded corner, ensuring that the underlying fundamental physical phenomena of turbulence and thermal mixing flow features are preserved. Finally, the pipe lengths of the model were calibrated to ensure there would be no interference of the upstream developing region and the outlet boundary conditions on the thermal mixing at the junction. A sample under-resolved DNS case, with unity and low-Prandtl number passive temperature scalars, with iso-temperature, iso-flux and mixed (Robin) wall boundary conditions, are presented. This proof-of-concept simulation contributes to the finalization of the set-up for fully-resolved DNS with respect to the computational grid size selection and transient characteristics.

DNS
Mixed boundary condition
Nek5000
T-junction
Thermal mixing

http://resolver.tudelft.nl/uuid:4e1072b9-9bd0-4348-a653-f2c177a61e4f

https://doi.org/10.1016/j.nucengdes.2023.112403

2023-12-04

0029-5493

Nuclear Engineering and Design, 410

Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.

Institutional Repository

journal article

© 2023 Aniketh Ajay Kumar, Akshat Mathur, M.I. Gerritsma, Ed Komen