Direct simulation and regularization modeling of turbulent thermal convection

Direct simulation and regularization modeling of turbulent thermal convection

van Reeuwijk, M.

Hanjalic, K. (promotor)

Applied Sciences

2007-03-12

This dissertation focuses on turbulent thermal convection, which occurs in a wide range of geophysical and engineering situations, such as the atmosphere, the sun, the earth's mantle, indoor climates etc. The first part of the thesis comprises a fundamental study of Rayleigh-BÉnard convection in a domain with aspect-ratio four. An ensemble of independent realizations, obtained by direct simulation, is processed with symmetry-accounted ensemble-averaging in order to distinguish the 'wind' from the fluctuations. Using this decomposition, the role of the wind and the behavior of the boundary layers is studied in detail. The second part is a study of the Leray-alpha model for wall-bounded flows. It is shown that the Leray-alpha model does not guarantee the filtered velocity field to be divergence-free in the presence of no-slip boundary conditions. Then, the Leray-alpha model is validated for three generic wall-bounded flows, i.e. plane channel flow, Rayleigh-BÉnard convection and the side-heated vertical channel. In the last part, the effects of truncation errors of finite difference approximations are included as low-pass filter operations in the Navier-Stokes equations. The resulting modified equations of the "numerical" fluid are studied to quantify the effect of discretizations on the turbulent energy spectrum.

turbulence
thermal
plume
buoyancy
regularization
regularisation
dns
leray
simulation
Rayleigh-Bénard
convection

http://resolver.tudelft.nl/uuid:8ffe1fb3-a0cd-4f7e-b4ea-9752aad913f4

978-90-9021652-2

Institutional Repository

doctoral thesis

(c) 2007 M. van Reeuwijk