Circulation, hydrographic structure and mixing at tidal fronts: the view from Georges Bank

1993 ◽  
Vol 343 (1669) ◽  
pp. 447-460 ◽  
Keyword(s):  
Field Studies ◽  
Temporal Variations ◽  
Tidal Mixing ◽  
Small Scale ◽  
Georges Bank ◽  
Tidal Period ◽  
Hydrographic Structure ◽  
Frontal Structure ◽  
Northern Side ◽  
Scale Turbulence

The steep slope on the northern side of Georges Bank and its location in the Fundy-Maine tidal system result in a persistent summertime frontal system comprising a tidal-mixing front and a stratified tide-topography interaction at the Bank edge. Recent field studies have provided a high-resolution description of the circulation, hydrographic structure and mixing in the region. Frontal features include an along-front residual jet, a surface convergence zone, regular variations in frontal structure and position over the tidal period and tidal modulation cycle, largeamplitude internal waves, and strong spatial and temporal variations in small-scale turbulence. The observations suggest that the magnitude of cross-front and vertical exchange in frontal regions can be site-specific depending on the relative importance of the underlying physical processes.

scholarly journals Effects of fluctuating energy input on the small scales in turbulence

2013 ◽  
Vol 737 ◽  
pp. 527-551 ◽  
Author(s):  
Chen-Chi Chien ◽  
Daniel B. Blum ◽  
Greg A. Voth
Keyword(s):  
Turbulent Flows ◽  
Energy Input ◽  
Large Scale ◽  
Similarity Theory ◽  
Three Dimensional ◽  
Structure Functions ◽  
Temporal Variations ◽  
Small Scale ◽  
Scale Turbulence ◽  
Kolmogorov Constant

AbstractIn the standard cascade picture of three-dimensional turbulent fluid flows, energy is input at a constant rate at large scales. Energy is then transferred to smaller scales by an intermittent process that has been the focus of a vast literature. However, the energy input at large scales is not constant in most real turbulent flows. We explore the signatures of these fluctuations of large-scale energy input on small-scale turbulence statistics. Measurements were made in a flow between oscillating grids, with ${R}_{\lambda } $ up to 262, in which temporal variations in the large-scale energy input can be introduced by modulating the oscillating grid frequency. We find that the Kolmogorov constant for second-order longitudinal structure functions depends on the magnitude of the fluctuations in the large-scale energy input. We can quantitatively predict the measured change with a model based on Kolmogorov’s refined similarity theory. The effects of fluctuations of the energy input can also be observed using structure functions conditioned on the instantaneous large-scale velocity. A linear parametrization using the curvature of the conditional structure functions provides a fairly good match with the measured changes in the Kolmogorov constant. Conditional structure functions are found to provide a more sensitive measure of the presence of fluctuations in the large-scale energy input than inertial range scaling coefficients.

Similarity of dissipation and enstrophy in particle-induced small-scale turbulence

2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Zhuo Wang ◽  
Kun Luo ◽  
Junhua Tan ◽  
Dong Li ◽  
Jianren Fan
Keyword(s):  
Small Scale ◽  
Scale Turbulence

scholarly journals Role of large-scale advection and small-scale turbulence on vertical migration of gyrotactic swimmers

2019 ◽  
Vol 4 (12) ◽  
Author(s):  
C. Marchioli ◽  
H. Bhatia ◽  
G. Sardina ◽  
L. Brandt ◽  
A. Soldati
Keyword(s):  
Vertical Migration ◽  
Large Scale ◽  
Small Scale ◽  
Scale Turbulence

scholarly journals Fabrication of freestanding Pt nanowires for use as thermal anemometry probes in turbulence measurements

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Hai Le-The ◽  
Christian Küchler ◽  
Albert van den Berg ◽  
Eberhard Bodenschatz ◽  
Detlef Lohse ◽  
...  
Keyword(s):  
Room Temperature ◽  
Fluid Velocity ◽  
Current Mode ◽  
Constant Current ◽  
Small Scale ◽  
Turbulence Measurements ◽  
High Dynamic ◽  
Scale Turbulence ◽  
Constant Current Mode ◽  
Pt Nanowires

AbstractWe report a robust fabrication method for patterning freestanding Pt nanowires for use as thermal anemometry probes for small-scale turbulence measurements. Using e-beam lithography, high aspect ratio Pt nanowires (~300 nm width, ~70 µm length, ~100 nm thickness) were patterned on the surface of oxidized silicon (Si) wafers. Combining wet etching processes with dry etching processes, these Pt nanowires were successfully released, rendering them freestanding between two silicon dioxide (SiO2) beams supported on Si cantilevers. Moreover, the unique design of the bridge holding the device allowed gentle release of the device without damaging the Pt nanowires. The total fabrication time was minimized by restricting the use of e-beam lithography to the patterning of the Pt nanowires, while standard photolithography was employed for other parts of the devices. We demonstrate that the fabricated sensors are suitable for turbulence measurements when operated in constant-current mode. A robust calibration between the output voltage and the fluid velocity was established over the velocity range from 0.5 to 5 m s−1 in a SF6 atmosphere at a pressure of 2 bar and a temperature of 21 °C. The sensing signal from the nanowires showed negligible drift over a period of several hours. Moreover, we confirmed that the nanowires can withstand high dynamic pressures by testing them in air at room temperature for velocities up to 55 m s−1.

scholarly journals 3–D Models of Galaxy Magnetic Fields with Spiral Shocks

1990 ◽  
Vol 140 ◽  
pp. 133-134
Author(s):  
J. Panesar ◽  
A.H. Nelson
Keyword(s):  
Gas Flow ◽  
Density Wave ◽  
Shock Velocity ◽  
Small Scale ◽  
Hydrodynamic Simulation ◽  
Dynamo Equation ◽  
Scale Turbulence ◽  
Wave Induced ◽  
The Magnetic Field ◽  
Stellar Density

We report here some preliminary results of 3–D numerical simulations of an α–ω dynamo in galaxies with differential rotation, small–scale turbulence, and a shock wave induced by a stellar density wave. We obtain the magnetic field from the standard dynamo equation, but include the spiral shock velocity field from a hydrodynamic simulation of the gas flow in a gravitational field with a spiral perturbation (Johns and Nelson, 1986).

THE PHENOMENOLOGY OF SMALL-SCALE TURBULENCE

1997 ◽  
Vol 29 (1) ◽  
pp. 435-472 ◽  
Author(s):  
K. R. Sreenivasan ◽  
R. A. Antonia
Keyword(s):  
Small Scale ◽  
Scale Turbulence

Aero-optics of subsonic turbulent boundary layers

2012 ◽  
Vol 696 ◽  
pp. 122-151 ◽  
Author(s):  
Kan Wang ◽  
Meng Wang
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Boundary Layers ◽  
Dominant Role ◽  
Elevation Angle ◽  
Turbulent Boundary Layers ◽  
Density Field ◽  
Small Scale ◽  
Number Range ◽  
Scale Turbulence

AbstractCompressible large-eddy simulations are carried out to study the aero-optical distortions caused by Mach 0.5 flat-plate turbulent boundary layers at Reynolds numbers of ${\mathit{Re}}_{\theta } = 875$, 1770 and 3550, based on momentum thickness. The fluctuations of refractive index are calculated from the density field, and wavefront distortions of an optical beam traversing the boundary layer are computed based on geometric optics. The effects of aperture size, small-scale turbulence, different flow regions and beam elevation angle are examined and the underlying flow physics is analysed. It is found that the level of optical distortion decreases with increasing Reynolds number within the Reynolds-number range considered. The contributions from the viscous sublayer and buffer layer are small, while the wake region plays a dominant role, followed by the logarithmic layer. By low-pass filtering the fluctuating density field, it is shown that small-scale turbulence is optically inactive. Consistent with previous experimental findings, the distortion magnitude is dependent on the propagation direction due to anisotropy of the boundary-layer vortical structures. Density correlations and length scales are analysed to understand the elevation-angle dependence and its relation to turbulence structures. The applicability of Sutton’s linking equation to boundary-layer flows is examined, and excellent agreement between linking equation predictions and directly integrated distortions is obtained when the density length scale is appropriately defined.

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