Temperature structure functions in the Bolgiano regime of thermal convection

Structure functions of turbulent temperature and velocity fluctuations are measured both for the atmosphere, in the surface layer over land, and for the laboratory, in the inner region of a thermal boundary layer and on the axis of a heated jet. Even-order temperature structure functions, up to order eight, generally compare favourably with the analysis of Antonia & Van Atta over the inertial subrange. The Reynolds number dependence of these structure functions, as predicted by the analysis, is in qualitative agreement with the measured data. Odd-order temperature structure functions depart significantly from the isotropic value of zero, particularly at large time delays. This departure is reasonably well predicted, over the inertial subrange, by postulating a simple ramp model for the temperature fluctuations. Assumptions involved in this model are directly tested by measurements in the heated jet. The ramp structure does not seriously affect either the even-order temperature structure functions or the mixed velocity-temperature functions, which include even-order moments of the temperature difference.

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Comparison between the sum of second‐order velocity structure functions and the second‐order temperature structure function

Physics of Fluids ◽

10.1063/1.869084 ◽

1996 ◽

Vol 8 (11) ◽

pp. 3105-3111 ◽

Cited By ~ 18

Author(s):

R. A. Antonia ◽

Y. Zhu ◽

F. Anselmet ◽

M. Ould‐Rouis

Keyword(s):

Structure Function ◽

Velocity Structure ◽

Structure Functions ◽

Second Order ◽

Temperature Structure

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Assessment of local isotropy using measurements in a turbulent plane jet

Journal of Fluid Mechanics ◽

10.1017/s0022112086002331 ◽

1986 ◽

Vol 163 ◽

pp. 365-391 ◽

Cited By ~ 57

Author(s):

R. A. Antonia ◽

F. Anselmet ◽

A. J. Chambers

Keyword(s):

Large Scale ◽

Spatial Organization ◽

Structure Functions ◽

Small Scale ◽

Temperature Structure ◽

Local Isotropy ◽

Large Scale Motion ◽

Turbulent Plane ◽

Scale Motion ◽

Plane Jet

Following a review of the difficulties associated with the measurement and interpretation of statistics of the small-scale motion, the evidence for and against local isotropy is assessed in the light of measurements in a turbulent plane jet at moderate values of the Reynolds and Péclet numbers. These measurements include spatial derivatives with respect to different spatial directions of the longitudinal velocity fluctuation and of the temperature fluctuation. Relations between mean-square values of these derivatives suggest strong departures from local isotropy for both velocity and temperature. In contrast, the locally isotropic forms of the vorticity and temperature dissipation budgets are approximately satisfied. Possible contamination of the fine-scale measurements by the anisotropic large-scale motion is assessed in the context of the measured structure functions of temperature and of the measured skewness of the streamwise derivative of temperature. Structure functions are, within the framework of local isotropy, consistent with the average frequency and amplitude of temperature signatures that characterize the quasi-organized large-scale motion. Conditional averages associated with this motion account, in an approximate way, for the skewness of the temperature derivative but make negligible contributions to the skewness of velocity derivatives. The degree of spatial organization of the fine structure is inferred from conditional statistics of temperature derivatives.

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