The computation of turbulent natural convection flows - Turbulence ...

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need fine numerical resolution near the walls. There are several WF strategies.
In this study, two of them have been investigated. One is a widely used con-
ventional method which is called the Standard Wall Function (SWF) and the
other one is a more recently developed method which is called the Analytical
Wall Function (AWF).
Several test cases have been investigated to test how different turbulence
models and near wall strategies perform in the simulation of a range of flows
driven by buoyancy forces. The test cases have been selected in order to cover
a wide range of physical phenomena.
The first family of test cases are tall cavities having different angles of incli-
nation. The angles of inclination range from a vertical and moderate angle of
90 ◦ , 60 ◦ , respectively, to highly inclined (15 ◦ and 5 ◦ ). For all cases apart from
the90 ◦ and5 ◦ , two configurations for the thermal boundary conditions are ex-
amined. One configuration is where the hot wall is located above the cold wall.
In this configuration, due to the existence of stable thermal stratification, it is
expected to see only weak turbulence mixing and heat transfer. In the other
configuration, with the hot wall located below the cold wall, due to existence
of unstable thermal stratification, it is expected to see stronger turbulence mix-
ing heat transfer.
The final test case concerns buoyancy-driven flow in an annular horizontal
penetration. One end of the annulus is closed and the other side is open to a
large volume of hot fluid. The surface of the inner annulus cylinder is set to a
cold temperature, and the aim of simulation is to explore how hot fluid pene-
trates inside the horizontal annulus from its open side. This test case provides
further challenges compared to the closed cavities test cases, due to the fact
that no inlet flow rate is imposed to the computational domain.