Turbulent natural convection in enclosure is a paradigmatic case for wide class of
processes of great interest for industrial and environmental problems.The solid-fluid
thermal interaction, the anisotropy of the turbulence intensity in the flow field along
with the transient nature of heat transfer processes, pose challenges regarding the
numerical modeling. The case of a square cavity with differently heated vertical
walls and two horizontal conductive plates is studied at Ra = 1.58 × 109. The study
is carried out numerically, using large-eddy simulation together with a dynamic
Lagrangian turbulence model and a conjugate heat transfer method to take into
account heat transfer at the solid surfaces. First, validation is carried out against the
literature experimental and numerical data. The results of validation tests evidence the
limitations of using the adiabatic conditions as a model for reproducing an insulator.
In fact, the adiabatic condition represents the asymptotic behavior which is often
difficult to reach in real conditions. Successively, the model is used to investigate the
effect on the flow field of different materials composing the horizontal walls. Initial
conditions representative of physical experiment are used. In order to reduce the
computational time required for a simulation with insulating materials at the walls,
a four-step temperature advancement strategy is proposed, based on the artificial
reduction-first and recover-later of the specific heat coefficient Cp of the materials
at different stages of the simulation. The conductivity of the solid media is found
to influence the flow configuration since heat transfer at the solid walls substantially
modifies the turbulent field and makes the flow field less homogeneous along the horizontal
direction.
