Sl. Christie et Ja. Domaradzki, SCALE DEPENDENCE OF THE STATISTICAL CHARACTER OF TURBULENT FLUCTUATIONS IN THERMAL-CONVECTION, Physics of fluids, 6(5), 1994, pp. 1848-1855
Two numerical realizations of thermal turbulence at Ra = 630 000 and a
t the disparate aspect ratios (AR) of 3.1 and 6 were shown previously
[Phys. Fluids A 5, 412 (1993)] to exhibit probability distribution fun
ctions (PDFs) of temperature flucuations (T'), which were exponential
in the former case and Gaussian in the latter. Such PDFs for T' are in
strumental in definitions of hard and soft turbulence regimes. Here th
e same two realizations are considered, but the fields are spectrally
decomposed by a horizontal scale before accumulating statistics. Withi
n either flow field, both Gaussianity and exponentiality are present,
but at differing lateral scales. The T' distributions are seen to be G
aussian in the large scales, and the exponential at the small ones wit
h parallel trends seen in the statistics of the velocity fields. Simil
arities with previous experimental and theoretical results and implica
tions for soft/hard turbulence classification are discussed.