Experimental and 3D numerical investigation of buoyancy-driven instabilities around a heated horizontal square cylinder within an enclosure
Résumé
This study addresses the natural convection flow driven by a
heated square cylinder within an air-filled enclosure for parameter
values corresponding to the onset of unsteadiness and weakly
transitional flow regime. 2D time-resolved PIV measurements
are jointly used with 2D and 3D numerical simulations, either
with full or linearized equations, to study the intrinsic 3D flow
instabilities. Two types of vortical structures develop within the
enclosure in the parallel and transverse directions to the cylinder
axis. The interaction between these convective cells initiates an
unsteady flow regime characterized by large scale eddies swaying
around the cylinder and wave oscillations which lead to the
generation of peculiar hook-shaped structures. Statistical and
spectral analyses of the flow help pointing up some noticeable
features of this unsteady flow such as the spectrum of the longitudinal
spatial modes that reveals a turbulence-like pattern with
unconventional slopes in the inertial and dissipative zones.