Abstract
The paper deals with the turbulent flow of liquid metal directed upwards in a vertical channel featuring a backward-facing step. The vertical wall behind the step is heated at various rates thereby inducing forced and mixed convection. Due to the low Prandtl number of liquid metal flow a data basis for this technically relevant flow type did not exist so far. Here, DNS and LES results are presented to provide detailed information about the statistics of the turbulent motion, budgets of turbulent kinetic energy and other quantities. This information is then further used to develop suitable statistical turbulence models capable of properly covering this flow and similar ones, i.e. forced, mixed and free convection of liquid metals. Finally, the paper reports on the construction of an experiment conceived for exactly the same configuration as simulated, with the purpose of close cross validation between the different approaches.
Highlights
The thermo-hydraulic behaviour of liquid metal flowing through a vertical backward facing step (BFS) is the subject of this study
Summary This article describes numerical and technical developments to investigate the vertical backward facing step (BFS) problem for a low Prandtl number medium such as liquid metals, appearing in several technical applications. In this context a quasi-exact solution of the flow has been developed, verified and validated by means of a turbulence resolved modelling of the flow problem based on a Direct numerical simulation (DNS) or a corresponding Direct Numerical Simulations (DNS) to serve as a reference solution
In this context the mean fluid wall interface temperatures are developed to provide an indication for the test-sectional set-up of the BFS experiments, but rather to describe the exact transport quantities for the momentum and temperature field wall normal to the heated section along the entire heated length to identify stagnation points and recirculation domains peculiar to any technical design
Summary
The thermo-hydraulic behaviour of liquid metal flowing through a vertical backward facing step (BFS) is the subject of this study. The flow separation due to sudden changes of the geometry like the BFS is of crucial importance for the thermo-hydraulic characterisation of various components like heat exchanger, thermal storage containers, manifolds and flow collectors. Such a sudden geometry change paired with an anisotropic heating profile causes flow stratification, stagnation points, re-circulation zones, etc. The flow over a BFS has been investigated frequently in the past for fluids with a Prandtl number around unity, like water or air. For low Prandtl number fluids like liquid metals (LM), the behaviour differs considerably.
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