Comparison between high-order velocity vector and temperature structure functions

1998 ◽  
Vol 57 (2) ◽  
pp. 2463-2466 ◽  
Author(s):  
R. A. Antonia ◽  
B. R. Pearson
Keyword(s):  
Velocity Vector ◽  
Structure Functions ◽  
High Order ◽  
Temperature Structure

Finite-Péclet-number effects on the scaling exponents of high-order passive scalar structure functions

2012 ◽  
Vol 713 ◽  
pp. 453-481 ◽  
Author(s):  
J. Lepore ◽  
L. Mydlarski
Keyword(s):  
Scalar Field ◽  
Boundary Conditions ◽  
Passive Scalar ◽  
Structure Functions ◽  
High Order ◽  
Field Boundary ◽  
Scaling Exponents ◽  
Heated Cylinder ◽  
Scalar Structure ◽  
The Difference

AbstractThe effect of scalar-field (temperature) boundary conditions on the inertial-convective-range scaling exponents of the high-order passive scalar structure functions is studied in the turbulent, heated wake downstream of a circular cylinder. The temperature field is generated two ways: using (i) a heating element embedded within the cylinder that generates the hydrodynamic wake (thus creating a heated cylinder) and (ii) a mandoline (an array of fine, heated wires) installed downstream of the cylinder. The hydrodynamic field is independent of the scalar-field boundary conditions/injection methods, and the same in both flows. Using the two heat injection mechanisms outlined above, the inertial-convective-range scaling exponents of the high-order passive scalar structure functions were measured. It is observed that the different scalar-field boundary conditions yield significantly different scaling exponents (with the magnitude of the difference increasing with structure function order). Moreover, the exponents obtained from the mandoline experiment are smaller than the analogous exponents from the heated cylinder experiment (both of which exhibit a significant departure from the Kolmogorov prediction). Since the observed deviation from the Kolmogorov $n/ 3$ prediction arises due to the effects of internal intermittency, the typical interpretation of this result would be that the scalar field downstream of the mandoline is more internally intermittent than that generated by the heated cylinder. However, additional measures of internal intermittency (namely the inertial-convective-range scaling exponents of the mixed, sixth-order, velocity–temperature structure functions and the non-centred autocorrelations of the dissipation rate of scalar variance) suggest that both scalar fields possess similar levels of internal intermittency – a distinctly different conclusion. Examination of the normalized high-order moments reveals that the smaller scaling exponents (of the high-order passive scalar structure functions) obtained for the mandoline experiment arise due to the smaller thermal integral length scale of the flow (i.e. the narrower inertial-convective subrange) and are not solely the result of a more intermittent scalar field. The difference in the passive scalar structure function scaling exponents can therefore be interpreted as an artifact of the different, finite Péclet numbers of the flows under consideration – an effect that is notably less prominent in the other measures of internal intermittency.

Numerical study of high-order Lagrangian structure functions in a turbulent channel flow with low Reynolds number

2010 ◽  
Vol 22 (S1) ◽  
pp. 215-218 ◽  
Author(s):  
Jian-ping Luo ◽  
Zhi-ming Lu ◽  
TatsLo Ushijima ◽  
Osami Kitoh ◽  
Xiang Qiu ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Channel Flow ◽  
Numerical Study ◽  
Low Reynolds Number ◽  
Turbulent Channel Flow ◽  
Structure Functions ◽  
High Order ◽  
Low Reynolds

Structure functions of temperature fluctuations in turbulent shear flows

1978 ◽  
Vol 84 (3) ◽  
pp. 561-580 ◽  
Author(s):  
R. A. Antonia ◽  
C. W. Van Atta
Keyword(s):  
Temperature Fluctuations ◽  
Structure Functions ◽  
Inertial Subrange ◽  
Turbulent Shear ◽  
Temperature Structure ◽  
Odd Order ◽  
Even Order ◽  
Inner Region ◽  
Heated Jet ◽  
Reynolds Number Dependence

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.

Assessment of local isotropy using measurements in a turbulent plane jet

1986 ◽  
Vol 163 ◽  
pp. 365-391 ◽  
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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