scholarly journals Determination of the turbulent energy dissipation rate from data measured by a “Stream Line” lidar in the atmospheric surface layer

2015 ◽  
Vol 28 (10) ◽  
Keyword(s):  
Surface Layer ◽  
Energy Dissipation ◽  
Dissipation Rate ◽  
Atmospheric Surface Layer ◽  
Turbulent Energy ◽  
Energy Dissipation Rate ◽  
Stream Line ◽  
Turbulent Energy Dissipation Rate

scholarly journals Analysis of the mechanism of gas bubble break-up in liquids during the self-aspirating impeller operation

2016 ◽  
Vol 37 (3) ◽  
pp. 441-457
Author(s):  
Jacek Stelmach ◽  
Czesław Kuncewicz ◽  
Radosław Musoski
Keyword(s):  
Energy Dissipation ◽  
Dissipation Rate ◽  
Turbulent Energy ◽  
Energy Dissipation Rate ◽  
Bubble Velocity ◽  
Gas Bubble ◽  
Turbulent Energy Dissipation Rate ◽  
Simplifying Assumptions ◽  
Break Up

Abstract Feasibility of a model of gas bubble break-up and coalescence in an air-lift column enabling determination of bubble size distributions in a mixer with a self-aspirating impeller has been attempted in this paper. According to velocity measurements made by the PIV method with a self-aspirating impeller and Smagorinski’s model, the spatial distribution of turbulent energy dissipation rate close to the impeller was determined. This allowed to positively verify the dependence of gas bubble velocity used in the model, in relation to turbulent energy dissipation rate. Furthermore, the range of the eddy sizes capable of breaking up the gas bubbles was determined. The verified model was found to be greatly useful, but because of the simplifying assumptions some discrepancies of experimental and model results were observed.

Turbulent energy dissipation rate measurements by coherent lidar

1995 ◽  
Author(s):  
Viktor A. Banakh ◽  
Natalia N. Kerkis ◽  
Igor N. Smalikho ◽  
Friedrich Koepp ◽  
Christian Werner
Keyword(s):  
Energy Dissipation ◽  
Dissipation Rate ◽  
Turbulent Energy ◽  
Energy Dissipation Rate ◽  
Turbulent Energy Dissipation Rate ◽  
Coherent Lidar

Transport equation for the mean turbulent energy dissipation rate on the centreline of a fully developed channel flow

2015 ◽  
Vol 777 ◽  
pp. 151-177 ◽  
Author(s):  
S. L. Tang ◽  
R. A. Antonia ◽  
L. Djenidi ◽  
H. Abe ◽  
T. Zhou ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Transport Equation ◽  
Channel Flow ◽  
Dissipation Rate ◽  
Turbulent Energy ◽  
Energy Dissipation Rate ◽  
Grid Turbulence ◽  
Normal Velocity ◽  
Turbulent Energy Dissipation Rate ◽  
The Mean

The transport equation for the mean turbulent energy dissipation rate $\overline{{\it\epsilon}}$ along the centreline of a fully developed channel flow is derived by applying the limit at small separations to the two-point budget equation. Since the ratio of the isotropic energy dissipation rate to the mean turbulent energy dissipation rate $\overline{{\it\epsilon}}_{iso}/\overline{{\it\epsilon}}$ is sufficiently close to 1 on the centreline, our main focus is on the isotropic form of the transport equation. It is found that the imbalance between the production of $\overline{{\it\epsilon}}$ due to vortex stretching and the destruction of $\overline{{\it\epsilon}}$ caused by the action of viscosity is governed by the diffusion of $\overline{{\it\epsilon}}$ by the wall-normal velocity fluctuation. This imbalance is intrinsically different from the advection-driven imbalance in decaying-type flows, such as grid turbulence, jets and wakes. In effect, the different types of imbalance represent different constraints on the relation between the skewness of the longitudinal velocity derivative $S_{1,1}$ and the destruction coefficient $G$ of enstrophy in different flows, thus resulting in non-universal approaches of $S_{1,1}$ towards a constant value as the Taylor microscale Reynolds number, $R_{{\it\lambda}}$, increases. For example, the approach is slower for the measured values of $S_{1,1}$ along either the channel or pipe centreline than along the axis in the self-preserving region of a round jet. The data for $S_{1,1}$ collected in different flows strongly suggest that, in each flow, the magnitude of $S_{1,1}$ is bounded, the value being slightly larger than 0.5.

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