Turbulent characteristics and energy transfer in the far field of active-grid turbulence

2021 ◽  
Vol 33 (11) ◽  
pp. 115119
Author(s):  
Y. Zheng ◽  
K. Nagata ◽  
T. Watanabe
Keyword(s):  
Energy Transfer ◽  
Grid Turbulence ◽  
Far Field ◽  
Active Grid ◽  
Turbulent Characteristics

Entrainment and mixing of water droplets across a shearless turbulent interface with and without gravitational effects

2011 ◽  
Vol 668 ◽  
pp. 293-303 ◽  
Author(s):  
S. GERASHCHENKO ◽  
G. GOOD ◽  
Z. WARHAFT
Keyword(s):  
Particle Concentration ◽  
Error Function ◽  
Stokes Number ◽  
Grid Turbulence ◽  
Integral Scale ◽  
Number Range ◽  
Gravitational Effects ◽  
Droplet Distribution ◽  
Active Grid ◽  
Kolmogorov Scale

We describe experiments of the entrainment and mixing of water (sub-Kolmogorov scale) droplets across a turbulent–non-turbulent interface (TNI) as well a turbulent–turbulent interface (TTI) in shearless grid turbulence, over a time scale in which evaporation is insignificant. The flow is produced by means of a splitter plate with an active grid and water sprays on one side and screens or an active grid on the other side. The Taylor microscale Reλ on the turbulent side is 275 and the average dissipation scale Stokes number, Stη ≈ 0.2, and based on the integral scale, Stl ≈ 0.003. By changing the orientation of the grid system, gravitational effects may be excluded or included. We show that in the absence of gravity, for the Stokes number range studied (0.06 ≤ Stη ≤ 1.33), the droplet distribution does not change across the interface. With gravity, the larger drops are selectively mixed and this is more pronounced for the TNI than for the TTI. The particle concentration distribution is an error function for the TTI but departs significantly for the TNI due to the intermittency in the flow. In terms of particle concentration, the entrainment is most efficient for the TTI with gravity. The results are related to droplet entrainment in clouds.

Passive scalar dispersion and mixing in a turbulent jet

1995 ◽  
Vol 292 ◽  
pp. 1-38 ◽  
Author(s):  
Chenning Tong ◽  
Z. Warhaft
Keyword(s):  
Reynolds Number ◽  
Cross Correlation ◽  
Thermal Field ◽  
Temperature Fluctuations ◽  
Passive Scalar ◽  
Turbulent Jet ◽  
Grid Turbulence ◽  
Far Field ◽  
The Cross ◽  
Heated Jet

The dispersion and mixing of passive scalar (temperature) fluctuations is studied in a turbulent jet. The temperature fluctuations were produced by heated fine wire rings placed axisymmetrically in the flow. Typically the ring diameters were of the same order as the jet, Dj, and they were placed in the self-similar region. However, other initial conditions were studied, including a very small diameter ring used to approximate a point source. Using a single ring to study dispersion (which is analogous to placing a line source in a planar flow such as grid turbulence), it was found that the intense local thermal field close to the ring disperses and fills the whole jet in approximately 1.5 eddy turnover times. Thereafter the thermal field evolves in the same way as for the traditional heated jet experiments. Two heated rings were used to study the mixing of two independently introduced scalar fields. Here an inference method (invoking the principle of superposition) was used to determine the evolution of the cross-correlation coefficient, ρ, and the segregation parameter, α, as well as the coherence and co-spectrum. While initially strongly dependent on ring locations and spacing, ρ and α reached asymptotic values of 1 and 0.04, respectively, also in about 1.5 eddy turnover times. These results are contrasted with mixing and dispersion in grid turbulence where the evolution is slower. Measurements in the far field of the jet (where ρ = 1) of the square of the scalar derivative conditioned on the scalar fluctuation itself, as well as other conditional statistics, showed strong dependence on the measurement location, as well as the direction in which the derivative was determined. The cross-correlation between the square of the scalar derivative and the signal showed a clear Reynolds-number trend, decreasing as the jet Reynolds number was varied from 2800 to 18 000. The far-field measurements, using the heated rings, were corroborated by new heated jet experiments.

Measurements of spectral energy transfer in grid turbulence

1969 ◽  
Vol 38 (4) ◽  
pp. 743-763 ◽  
Author(s):  
C. W. Van Atta ◽  
W. Y. Chen
Keyword(s):  
Energy Transfer ◽  
Dynamical Equation ◽  
Isotropic Turbulence ◽  
Three Dimensional ◽  
Direct Interaction ◽  
Spectral Energy ◽  
Grid Turbulence ◽  
Local Isotropy ◽  
Isotropic Energy ◽  
Direct Interaction Approximation

Direct measurements of the energy transfer spectrum in locally isotropic grid turbulence have been used to determine the extent of validity for grid turbulence of the dynamical equation for the three-dimensional energy spectrum in isotropic turbulence. The extent of applicability of the isotropic energy balance is consistent with the usual local isotropy criterion based on energy spectra alone.The present results are in general agreement with some previous measurements by Uberoi, who determined the transfer spectrum assuming the strict validity of the isotropic dynamical equation. The measured energy transfer spectra are quantitatively similar to those calculated by Kraichnan using the direct-interaction approximation.

scholarly journals Turbulent Characteristics near Free Surface of an Oscillating-Grid Turbulence Field

1995 ◽  
Vol 39 ◽  
pp. 819-826
Author(s):  
Toshimitsu KOMATSU ◽  
Toshihiko SHIBATA ◽  
Koji ASAI ◽  
Kentaro TAKAHARA
Keyword(s):  
Free Surface ◽  
Grid Turbulence ◽  
Turbulent Characteristics ◽  
Oscillating Grid

Energy Transfer in Spectra of the d-Dimensional Past Grid Turbulence

2006 ◽  
Vol 46 (5) ◽  
pp. 1254-1276
Author(s):  
M. Hnatich ◽  
S. Sprinc ◽  
M. Stehlik ◽  
F. Tomasz
Keyword(s):  
Energy Transfer ◽  
Grid Turbulence

scholarly journals Correlating Nanoscopic Energy Transfer and Far-Field Emission to Unravel Lasing Dynamics in Plasmonic Nanocavity Arrays

Nano Letters ◽  
2018 ◽  
Vol 18 (2) ◽  
pp. 1454-1459 ◽  
Author(s):  
Claire Deeb ◽  
Zhi Guo ◽  
Ankun Yang ◽  
Libai Huang ◽  
Teri W. Odom
Keyword(s):  
Energy Transfer ◽  
Field Emission ◽  
Far Field ◽  
Lasing Dynamics
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