Locally averaged thermal dissipation rate in turbulent thermal convection: A decomposition into contributions from different temperature gradient components
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AbstractUsing a homemade local temperature gradient probe, the instantaneous thermal dissipation rate epsilon(T)(r, t) is obtained in an aspect-ratio-one cylindrical convection cell filled with water. From the time series measurements, a locally averaged thermal dissipation epsilon(tau)(r, t) over a time interval tau is constructed. Herein we decompose epsilon(tau)(r, t) into three contributions epsilon(i)(tau)(r, t) (i = x, y, z) from the temperature gradient components in the x, y, and z directions and systematically study their statistics and scaling properties. It is found that the moments of epsilon(i)(tau)(r, t) exhibit good scaling in tau, i.e., <(epsilon(i)(tau))(p)> similar to tau(mu i(p)), for all three components and for p up to 6. The obtained exponents mu(i)(p) at three representative locations in the convection cell are explained by a phenomenological model, which combines the effects of velocity statistics and geometric shape of the most dissipative structures in turbulent convection. (C) 2011 American Institute of Physics. [doi:10.1063/1.3555637]
All Author(s) ListHe XZ, Ching ESC, Tong PE
Journal namePhysics of Fluids
Volume Number23
Issue Number2
PublisherAIP Publishing
LanguagesEnglish-United Kingdom
Web of Science Subject CategoriesMechanics; MECHANICS; Physics; Physics, Fluids & Plasmas; PHYSICS, FLUIDS & PLASMAS

Last updated on 2020-25-11 at 00:20