Inner scale of turbulence as derived from NAVSLaM and applied to measurements of scintillation

2021 ◽  
Author(s):  
Rita Mahon ◽  
Christopher I. Moore ◽  
Mike S. Ferraro ◽  
William S. Rabinovich ◽  
Paul A. Frederickson
Keyword(s):  
Inner Scale

Fractal-like actuator disc theory for optimal energy extraction

2021 ◽  
Vol 927 ◽  
Author(s):  
D. Dehtyriov ◽  
A.M. Schnabl ◽  
C.R. Vogel ◽  
S. Draper ◽  
T.A.A. Adcock ◽  
...  
Keyword(s):  
Extraction Process ◽  
Power Coefficient ◽  
Finite Width ◽  
Energy Extraction ◽  
Optimal Arrangement ◽  
Planar System ◽  
Power Extraction ◽  
Multi Scale ◽  
Actuator Disc ◽  
Inner Scale

The limit of power extraction by a device which makes use of constructive interference, i.e. local blockage, is investigated theoretically. The device is modelled using actuator disc theory in which we allow the device to be split into arrays and these then into sub-arrays an arbitrary number of times so as to construct an $n$ -level multi-scale device in which the original device undergoes $n-1$ sub-divisions. The alternative physical interpretation of the problem is a planar system of arrayed turbines in which groups of turbines are homogeneously arrayed at the smallest $n\mathrm {th}$ scale, and then these groups are homogeneously spaced relative to each other at the next smallest $n-1\mathrm {th}$ scale, with this pattern repeating at all subsequent larger scales. The scale-separation idea of Nishino & Willden (J. Fluid. Mech., vol. 708, 2012b, pp. 596–606) is employed, which assumes mixing within a sub-array occurs faster than mixing of the by-pass flow around that sub-array, so that in the $n$ -scale device mixing occurs from the inner scale to the outermost scale in that order. We investigate the behaviour of an arbitrary level multi-scale device, and determine the arrangement of actuator discs ( $n\mathrm {th}$ level devices) which maximises the power coefficient (ratio of power extracted to undisturbed kinetic energy flux through the net disc frontal area). We find that this optimal arrangement is close to fractal, and fractal arrangements give similar results. With the device placed in an infinitely wide channel, i.e. zero global blockage, we find that the optimum power coefficient tends to unity as the number of device scales tends to infinity, a 27/16 increase over the Lanchester–Betz limit of $0.593$ . For devices in finite width channels, i.e. non-zero global blockage, similar observations can be made with further uplift in the maximum power coefficient. We discuss the fluid mechanics of this energy extraction process and examine the scale distribution of thrust and wake velocity coefficients. Numerical demonstration of performance uplift due to multi-scale dynamics is also provided. We demonstrate that bypass flow remixing and ensuing energy losses increase the device power coefficient above the limits for single devices, so that although the power coefficient can be made to increase, this is at the expense of the overall efficiency of energy extraction which decreases as wake-scale remixing losses necessarily rise. For multi-scale devices in finite overall blockage two effects act to increase extractable power; an overall streamwise pressure gradient associated with finite blockage, and wake pressure recoveries associated with bypass-scale remixing.

Refractivity turbulence, inner scale, and eddy dissipation rate observations using a balloon-ring platform

2003 ◽  
Author(s):  
Frank D. Eaton ◽  
Patrick R. Kelly ◽  
Demos T. Kyrazis ◽  
Sheldon D. Stokes
Keyword(s):  
Dissipation Rate ◽  
Inner Scale

Evidence for an inner scale to the density turbulence in the interstellar medium

1990 ◽  
Vol 353 ◽  
pp. L29 ◽  
Author(s):  
Steven R. Spangler ◽  
Carl R. Gwinn
Keyword(s):  
Interstellar Medium ◽  
Inner Scale

scholarly journals Effects of Oceanic Turbulence on Orbital Angular Momenta of Optical Communications

2020 ◽  
Vol 8 (11) ◽  
pp. 869
Author(s):  
Shuang Zhai ◽  
Yun Zhu ◽  
Yixin Zhang ◽  
Zhengda Hu
Keyword(s):  
Dissipation Rate ◽  
Quantum Coherence ◽  
Single Photon ◽  
Beam Width ◽  
Communication Performance ◽  
Oceanic Turbulence ◽  
Angular Momenta ◽  
Optimal Beam ◽  
Lower Temperature ◽  
Inner Scale

The propagation properties of Laguerre-Gaussian beams in oceanic turbulence are investigated for both single-photon and biphoton cases. For single-photon communication, the channel capacity and trace distance are employed, both of which effectively reveal the communication performance via different viewpoints. For the biphoton case, we consider distributions of quantum resources including entanglement and quantum coherence. Turbulence conditions with a larger inner-scale and anisotropic factors, higher dissipation rate of kinetic energy, lower dissipation rate of the mean-squared temperature, and lower temperature-salinity contribution ratio combined with longer wavelength and an appropriate range of optimal beam width are beneficial to communication performances. Our results provide theoretical significance to improve the orbital-angular-momentum communication via oceanic turbulence.

Mechanical Properties and Marine Corrosion Resistance of P-Bearing ULCB Steels

2010 ◽  
Vol 654-656 ◽  
pp. 378-381 ◽  
Author(s):  
Wen Fang Cui ◽  
Chun Ming Liu ◽  
Si Xun Zhang
Keyword(s):  
Mechanical Properties ◽  
Corrosion Resistance ◽  
Strengthening Effect ◽  
Marine Corrosion ◽  
Immersion Corrosion ◽  
P Content ◽  
Temperature Impact ◽  
Solution Strengthening ◽  
Low Temperature Impact Toughness ◽  
Inner Scale

The research aims to evaluate the microstructure, mechanical properties and marine corrosion resistance of P-bearing ULCB steels. P produced stronger solution strengthening effect, but had less effect on the low temperature impact toughness of ULCB steel. With increasing P content to 0.09(mass)%, the immersion corrosion rate of ULCB steel in 3.5% NaCl obviously decreased in comparison with those steels without or with lower P content. This is attributed to that the complex effect of Cu and P promoted the formation of dense amorphous oxyhydroxide in the inner scale, which inhibited further corrosion from NaCl solution. Mo in ULCB steel played an important role in avoiding pitting corrosion in Cl- environment.

Deformation and Fracture Behavior of Surface Oxide Scale on Fe-13Cr Alloy in Hot-Rolling Process

2006 ◽  
Vol 522-523 ◽  
pp. 461-468 ◽  
Author(s):  
Y. Hidaka ◽  
T. Anraku ◽  
Nobuo Otsuka
Keyword(s):  
Oxide Scale ◽  
Hot Rolling ◽  
Reduction Rate ◽  
Rolling Process ◽  
Surface Oxide ◽  
Rolling Reduction ◽  
Outer Scale ◽  
Hot Rolling Process ◽  
Micro Cracks ◽  
Inner Scale

The behavior of the surface oxide scale on steel products during hot rolling process influences the surface properties of final products. To investigate the deformation and the fracture behavior of surface oxide scale of Fe-13Cr alloy, a hot rolling test was carried out. The oxide scale rolled out was observed in detail by using TEM. The specimen was hot-rolled after oxidation at 1100 for 90 minutes in air. The hot rolling tests with two conditions (. The hot rolling test of the outer scale {=whole layer scale} , . The hot rolling test of the inner scale that removed the outer scale) were carried out. The rolling reduction rate was 25, 44, 58, and 68%. The outer scale was composed of Fe2O3 and F3O4, and the inner scale was composed of Fe3O4, FeCr2O4, and a small amount of Fe2SiO4. Fe2SiO4 formed along the grain boundaries of the other oxides (Fe3O4, FeCr2O4) was observed by TEM. In the test , Fe2O3 of the outer scale was pulverized to fine particle that looks like red powder, and Fe3O4 of the outer scale was cracked by hot rolling. A ductility-like behavior was observed in the inner scale (Test ). That is, it was found by the SEM observation that porosity and micro cracks of the surface oxide disappeared gradually according to the increase in the rolling reduction. It was thought that the porosity and the micro cracks eased the compression stress caused by hot rolling. In the case of high reduction rate, FeSi2O4 ,which is a low melting point oxide, formed on grain boundary caused grain boundary slipping. When the rolling reduction is very high, plastic deformation by dislocation occurred in Fe3O4 and FeCr2O4. However, these oxides were broken, when their plasticity would not be able to accept considerably high rolling reduction.

Sign in / Sign up

Export Citation Format

Share Document