Effects of Counter-Swell on Both the Mean Current and Turbulent Structure Below the Wind-Waves

2013 ◽  
pp. 115-120
Author(s):  
Shinjiro Mizuno
Keyword(s):  
Wind Waves ◽  
Turbulent Structure ◽  
The Mean ◽  
Mean Current

scholarly journals Gerstner waves in the presence of mean currents and rotation

2017 ◽  
Vol 820 ◽  
pp. 511-528 ◽  
Author(s):  
A. Constantin ◽  
S. G. Monismith
Keyword(s):  
Free Surface ◽  
Wind Waves ◽  
Nonlinear Phenomenon ◽  
Fast Mode ◽  
Lagrangian Analysis ◽  
Vertical Scale ◽  
The Mean ◽  
Gerstner Waves ◽  
Mean Current ◽  
O 10

We present a Lagrangian analysis of nonlinear surface waves propagating zonally on a zonal current in the presence of the Earth’s rotation that shows the existence of two modes of wave motion. The first, ‘fast’ mode, one with wavelengths commonly found for wind waves and swell in the ocean, represents the wave–current interaction counterpart of the rotationally modified Gerstner waves found first by Pollard (J. Geophys. Res., vol. 75, 1970, pp. 5895–5898) that quite closely resemble Stokes waves. The second, slower, mode has a period nearly equal to the inertial period and has a small vertical scale such that very long, e.g. $O(10^{4}~\text{km})$ wavelength, waves have velocities etc. that decay exponentially from the free surface over a scale of $O(10~\text{m})$ that is proportional to the strength of the mean current. In both cases, the particle trajectories are closed in a frame of reference moving with the mean current, with particle motions in the second mode describing inertial circles. Given that the linear analysis of the governing Eulerian equations only captures the fast mode, the slow mode is a fundamentally nonlinear phenomenon in which very small free surface deflections are manifestations of an energetic current.

scholarly journals On the performance of a photosystem II reaction centre-based photocell

2017 ◽  
Vol 8 (10) ◽  
pp. 6871-6880 ◽  
Author(s):  
Richard Stones ◽  
Hoda Hossein-Nejad ◽  
Rienk van Grondelle ◽  
Alexandra Olaya-Castro
Keyword(s):  
Photosystem Ii ◽  
Current Noise ◽  
Reaction Centre ◽  
Electron Counting ◽  
The Mean ◽  
Counting Statistics ◽  
Mean Current

We investigate the performance of a theoretical photosystem II reaction centre-inspired photocell device through the framework of electron counting statistics. In particular we look at the effect of a structured vibrational environment on the mean current and current noise.

scholarly journals Submesoscale Instability and Generation of Mesoscale Anticyclones near a Separation of the California Undercurrent

2015 ◽  
Vol 45 (3) ◽  
pp. 613-629 ◽  
Author(s):  
M. Jeroen Molemaker ◽  
James C. McWilliams ◽  
William K. Dewar
Keyword(s):  
Computational Grid ◽  
Relative Vorticity ◽  
Monterey Bay ◽  
Depth Range ◽  
Narrow Strip ◽  
Centrifugal Instability ◽  
The Mean ◽  
Flow Inertia ◽  
Mean Current ◽  
Current Pathway

AbstractThe California Undercurrent (CUC) flows poleward mostly along the continental slope. It develops a narrow strip of large negative vertical vorticity through the turbulent boundary layer and bottom stress. In several downstream locations, the current separates, aided by topographic curvature and flow inertia, in particular near Point Sur Ridge, south of Monterey Bay. When this happens the high-vorticity strip undergoes rapid instability that appears to be mesoscale in “eddy-resolving” simulations but is substantially submesoscale with a finer computational grid. The negative relative vorticity in the CUC is larger than the background rotation f, and Ertel potential vorticity is negative. This instigates ageostrophic centrifugal instability. The submesoscale turbulence is partly unbalanced, has elevated local dissipation and mixing, and leads to dilution of the extreme vorticity values. Farther downstream, the submesoscale activity abates, and the remaining eddy motions exhibit an upscale organization into the mesoscale, resulting in long-lived coherent anticyclones in the depth range of 100–500 m (previously called Cuddies) that move into the gyre interior in a generally southwestward direction. In addition to the energy and mixing effects of the postseparation instability, there is are significant local topographic form stress and bottom torque that retard the CUC and steer the mean current pathway.

Experimental study of the initial stages of wind waves' spatial evolution

2011 ◽  
Vol 681 ◽  
pp. 462-498 ◽  
Author(s):  
DAN LIBERZON ◽  
LEV SHEMER
Keyword(s):  
Energy Transfer ◽  
Growth Rates ◽  
Water Surface ◽  
Wind Waves ◽  
Pressure Fluctuations ◽  
Theoretical Models ◽  
Small Scale ◽  
Wave Flume ◽  
Spatial Growth ◽  
The Mean

Despite a significant progress and numerous publications over the last few decades a comprehensive understanding of the process of waves' excitation by wind still has not been achieved. The main goal of the present work was to provide as comprehensive as possible set of experimental data that can be quantitatively compared with theoretical models. Measurements at various air flow rates and at numerous fetches were carried out in a small scale, closed-loop, 5 m long wind wave flume. Mean airflow velocity and fluctuations of the static pressure were measured at 38 vertical locations above the mean water surface simultaneously with determination of instantaneous water surface elevations by wave gauges. Instantaneous fluctuations of two velocity components were recorded for all vertical locations at a single fetch. The water surface drift velocity was determined by the particle tracking velocimetry (PTV) method. Evaluation of spatial growth rates of waves at various frequencies was performed using wave gauge records at various fetches. Phase relations between various signals were established by cross-spectral analysis. Waves' celerities and pressure fluctuation phase lags relative to the surface elevation were determined. Pressure values at the water surface were determined by extrapolating the measured vertical profile of pressure fluctuations to the mean water level and used to calculate the form drag and consequently the energy transfer rates from wind to waves. Directly obtained spatial growth rates were compared with those obtained from energy transfer calculations, as well as with previously available data.

Effect of different connection modes of electromagnets on the performance of levitation control

2018 ◽  
Vol 232 (8) ◽  
pp. 2111-2125 ◽  
Author(s):  
Zhang Min ◽  
Gao Chang ◽  
MA Weihua
Keyword(s):  
Vertical Direction ◽  
Vertical Motion ◽  
Vertical Displacement ◽  
Control Mode ◽  
Adjustment Process ◽  
Dynamic Adjustment ◽  
Series Connection ◽  
Relative Safety ◽  
The Mean ◽  
Mean Current

In medium- and low-speed maglev vehicles, each levitation module contains four electromagnetic coils. In order to find a better coil control mode, the difference between the series connection in the control mode of the first and third coils (M1,3) and the series connection in the control mode of the first and second coils (M1,2) was analysed in this paper. By applying a malposition excitation of +2 mm in the vertical direction of the track for comparing the dynamic adjustment processes of the levitation module (including the vertical motion and rotation) in the two control modes, according to the current fluctuation in the coils in the above processes, the extreme position parameters and the mean current values during the adjustment were obtained. The adjustment process was analysed based on the instantaneous levitation force and the torque of the plate at the extreme positions in different control modes; the performance of the levitation module in the adjustment process and during the fluctuation of the coil current was analysed. The results indicate that for the dangerous ends at the two extreme positions in the selected working condition, the vertical displacement in M1,3 reduces by 11.11 and 48.98%, respectively, compared with that in M1,2. In the whole adjustment process, the mean current of the front and rear controllers in M1,3 reduces by 0.25 and 0.36 A, respectively. Therefore, it has been concluded that with regard to the relative safety and coil heating during vibration of the levitation module, M1,3 performs better than M1,2.

State-dependent modification of ATP-sensitive K+ channels by phosphatidylinositol 4,5-bisphosphate

2001 ◽  
Vol 280 (2) ◽  
pp. C303-C308 ◽  
Author(s):  
Midori Okamura ◽  
Masafumi Kakei ◽  
Koutaro Ichinari ◽  
Akihiro Miyamura ◽  
Naoya Oketani ◽  
...  
Keyword(s):  
Guinea Pigs ◽  
Ventricular Myocytes ◽  
Free Solution ◽  
K Channels ◽  
State Dependent ◽  
The Mean ◽  
Dependent Modification ◽  
Mean Current ◽  
Inside Out

With inside-out patch recordings in ventricular myocytes from the hearts of guinea pigs, we studied ATP-sensitive K+ (KATP) channels activated by phosphatidylinositol 4,5-bisphosphate (PIP2) with respect to sensitivity to ATP when in either a rundown state (RS) or a non-rundown state (NRS). Rundown of KATP channels was induced by exposure either to ATP-free solution or to ATP-free solution containing 19 μM Ca2+. Exposure of membrane patches to 10 μM PIP2 reactivated channels with both types of rundown. The reactivation by PIP2 did not require ATP in the bath. The IC50 of channels recovered from RS and before the rundown was 37.1 and 31.1 μM, respectively. PIP2irreversibly increased the mean current when the channel was in the NRS. This was associated with a shift of IC50 to 250.6 μM after PIP2 exposure. PIP2 activates NRS KATP channels by decreasing their sensitivity to ATP, whereas PIP2 reactivates RS-KATP channels independently of ATP without changing ATP sensitivity.

scholarly journals The interaction of free Rossby waves with semi-transparent equatorial waveguide – wave-mean flow interaction

2009 ◽  
Vol 16 (3) ◽  
pp. 381-392 ◽  
Author(s):  
G. M. Reznik ◽  
V. Zeitlin
Keyword(s):  
Rossby Waves ◽  
Landau Equation ◽  
Spatial Modulation ◽  
Equilibrium Solutions ◽  
Mean Flow ◽  
Ginzburg Landau ◽  
Baroclinic Waves ◽  
Ginzburg Landau Equation ◽  
The Mean ◽  
Mean Current

Abstract. Nonlinear interactions of the barotropic Rossby waves propagating across the equator with trapped baroclinic Rossby or Yanai modes and mean zonal flow are studied within the two-layer model of the atmosphere, or the ocean. It is shown that the equatorial waveguide with a mean current acts as a resonator and responds to barotropic waves with certain wavenumbers by making the trapped baroclinic modes grow. At the same time the equatorial waveguide produces the barotropic response which, via nonlinear interaction with the mean equatorial current and with the trapped waves, leads to the saturation of the growing modes. The excited baroclinic waves can reach significant amplitudes depending on the magnitude of the mean current. In the absence of spatial modulation the nonlinear saturation of thus excited waves is described by forced Landau-type equation with one or two attracting equilibrium solutions. In the latter case the spatial modulation of the baroclinic waves is expected to lead to the formation of characteristic domain-wall defects. The evolution of the envelopes of the trapped Rossby waves is governed by driven Ginzburg-Landau equation, while the envelopes of the Yanai waves obey the "first-order" forced Ginzburg-Landau equation. The envelopes of short baroclinic Rossby waves obey the damped-driven nonlinear Schrodinger equation well studied in the literature.

ELECTROMETRIC SENSITIVITY OF THE SINGLE ELECTRON TRANSISTOR

1992 ◽  
Vol 06 (22) ◽  
pp. 3555-3574 ◽  
Author(s):  
WOLFRAM KRECH ◽  
ANDREAS HÄDICKE ◽  
HEINZ-OLAF MÜLLER
Keyword(s):  
Shot Noise ◽  
Single Electron Transistor ◽  
Driving Voltage ◽  
Electromagnetic Environment ◽  
External Voltage ◽  
Noise Parameters ◽  
Double Junction ◽  
The Mean ◽  
Mean Current ◽  
External Charge

The essential part of the SET electrometer is the so-called SET transistor which consists of two serially coupled SET junctions driven by an external voltage. An external charge is influenced on the island between the two junctions. Furthermore, the influence of the electromagnetic environment is modelled by an additional impedance in the circuit. Using as well the two-state as the three-state approach, the mean-current through the double-junction, the shot-noise parameters and the charge sensitivity are calculated as a function of the driving voltage and the external charge on the island.

scholarly journals The Role of Wave-Induced Coriolis–Stokes Forcing on the Wind-Driven Mixed Layer

2005 ◽  
Vol 35 (4) ◽  
pp. 444-457 ◽  
Author(s):  
Jeff A. Polton ◽  
David M. Lewis ◽  
Stephen E. Belcher
Keyword(s):  
Analytical Solution ◽  
Observational Data ◽  
Mixed Layer ◽  
Analytical Solutions ◽  
Eddy Viscosity ◽  
Large Eddy Simulations ◽  
Current Profile ◽  
Large Eddy ◽  
The Mean ◽  
Mean Current

Abstract The interaction between the Coriolis force and the Stokes drift associated with ocean surface waves leads to a vertical transport of momentum, which can be expressed as a force on the mean momentum equation in the direction along wave crests. How this Coriolis–Stokes forcing affects the mean current profile in a wind-driven mixed layer is investigated using simple models, results from large-eddy simulations, and observational data. The effects of the Coriolis–Stokes forcing on the mean current profile are examined by reappraising analytical solutions to the Ekman model that include the Coriolis–Stokes forcing. Turbulent momentum transfer is modeled using an eddy-viscosity model, first with a constant viscosity and second with a linearly varying eddy viscosity. Although the Coriolis–Stokes forcing penetrates only a small fraction of the depth of the wind-driven layer for parameter values typical of the ocean, the analytical solutions show how the current profile is substantially changed through the whole depth of the wind-driven layer. It is shown how, for this oceanic regime, the Coriolis–Stokes forcing supports a fraction of the applied wind stress, changing the boundary condition on the wind-driven component of the flow and hence changing the current profile through all depths. The analytical solution with the linearly varying eddy viscosity is shown to reproduce reasonably well the effects of the Coriolis–Stokes forcing on the current profile computed from large-eddy simulations, which resolve the three-dimensional overturning motions associated with the turbulent Langmuir circulations in the wind-driven layer. Last, the analytical solution with the Coriolis–Stokes forcing is shown to agree reasonably well with current profiles from previously published observational data and certainly agrees better than the standard Ekman model. This finding provides evidence that the Coriolis–Stokes forcing is an important mechanism in controlling the dynamics of the upper ocean.

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