scholarly journals Complex environmental beta-plane turbulence: laboratory experiments with altimetric imaging velocimetry

2015 ◽  
Vol 2 (6) ◽  
pp. 1507-1529 ◽  
Author(s):  
A. M. Matulka ◽  
Y. Zhang ◽  
Y. D. Afanasyev
Keyword(s):  
Fresh Water ◽  
Turbulent Flows ◽  
Laboratory Experiments ◽  
Surface Elevation ◽  
Spectral Analyses ◽  
Zonal Jets ◽  
Alternating Direction ◽  
Beta Plane ◽  
Heating Water ◽  
Universal Properties

Abstract. Results from the spectral analyses of the flows in two experiments where turbulent flows were generated in a rotating tank with topographic β-effect, are presented. The flows were forced either by heating water from below or supplying fresh water at the top of saline layer. The flow was essentially barotropic in the first experiment and baroclinic in the second experiment. The gradient of the surface elevation was measured using optical altimetry (Altimetric Imaging Velocimetry). Multiple zonal jets of alternating direction were observed in both experiments. Turbulent cascades of energy exhibit certain universal properties in spite of the different nature of flows in the experiments.

scholarly journals Complex environmental <i>β</i>-plane turbulence: laboratory experiments with altimetric imaging velocimetry

2016 ◽  
Vol 23 (1) ◽  
pp. 21-29
Author(s):  
A. M. Matulka ◽  
Y. Zhang ◽  
Y. D. Afanasyev
Keyword(s):  
Fresh Water ◽  
Turbulent Flows ◽  
Laboratory Experiments ◽  
Surface Elevation ◽  
Spectral Analyses ◽  
Zonal Jets ◽  
Alternating Direction ◽  
Heating Water ◽  
Universal Properties

Abstract. Results from the spectral analyses of the flows in two experiments where turbulent flows were generated in a rotating tank with a topographic β-effect are presented. The flows were forced either by heating water from below or supplying fresh water at the top of a saline layer. The flow was essentially barotropic in the first experiment and baroclinic in the second experiment. The gradient of the surface elevation was measured using optical altimetry (altimetric imaging velocimetry). Multiple zonal jets of alternating direction were observed in both experiments. Turbulent cascades of energy exhibit certain universal properties in spite of the different natures of flows in the experiments.

scholarly journals A theory for the emergence of coherent structures in beta-plane turbulence

2014 ◽  
Vol 740 ◽  
pp. 312-341 ◽  
Author(s):  
Nikolaos A. Bakas ◽  
Petros J. Ioannou
Keyword(s):  
Turbulent Flows ◽  
Coherent Structures ◽  
Energy Input ◽  
Large Scale ◽  
Order Approximation ◽  
Plane Channel ◽  
Phase Speed ◽  
Homogeneous State ◽  
Zonal Jets ◽  
Beta Plane

AbstractPlanetary turbulent flows are observed to self-organize into large-scale structures such as zonal jets and coherent vortices. One of the simplest models of planetary turbulence is obtained by considering a barotropic flow on a beta-plane channel with turbulence sustained by random stirring. Nonlinear integrations of this model show that as the energy input rate of the forcing is increased, the homogeneity of the flow is broken with the emergence of non-zonal, coherent, westward propagating structures and at larger energy input rates by the emergence of zonal jets. We study the emergence of non-zonal coherent structures using a non-equilibrium statistical theory, stochastic structural stability theory (S3T, previously referred to as SSST). S3T directly models a second-order approximation to the statistical mean turbulent state and allows the identification of statistical turbulent equilibria and study of their stability. Using S3T, the bifurcation properties of the homogeneous state in barotropic beta-plane turbulence are determined. Analytic expressions for the zonal and non-zonal large-scale coherent flows that emerge as a result of structural instability are obtained. Through numerical integrations of the S3T dynamical system, it is found that the unstable structures equilibrate at finite amplitude. Numerical simulations of the nonlinear equations confirm the characteristics (scale, amplitude and phase speed) of the structures predicted by S3T.

Evaluation of acute toxicity of zinc, lead and cadmium to zooplanktonic community in upper Berach river system, Rajasthan, India

2012 ◽  
Vol 2 (1) ◽  
pp. 20-26
Author(s):  
Nadim Chishty ◽  
Anil Tripathi ◽  
Madhusudan Sharma
Keyword(s):  
Heavy Metal ◽  
Acute Toxicity ◽  
Fresh Water ◽  
River Basin ◽  
Laboratory Experiments ◽  
River System ◽  
Daphnia Lumholtzi ◽  
Lead And Cadmium ◽  
Sensitivity Pattern ◽  
Static Bioassay

Current study investigated through static bioassay, the acute toxicity of Zinc,Lead and Cadmium to fresh water zooplankters in the upper Berach riversystem which is a part of Gangetic river system. The river basin stretchesfrom Madar tank to Sarjana tank with a total length of 46 Km, including ninewater bodies i.e. Bada madar tank (73‹36f0ffE and 24‹38f0hN ), Chhotamadar tank, Fateh sagar lake, Udaisagar lake, Up]stream pond (Bichhdi]I),Down]stream pond(Bichhdi]II), Gadwa, Daroli and Sarjana tank (73‹ 57f10hEand 24‹14f30h N). Whole zooplanktonic communities were exposed to different heavy metal stresses. Exposed zooplanktonic community included nine planktonic forms i.e. Heliodiaptomus viduus, Mesocyclops hyalinus, Heterocypris, Daphnia lumholtzi, Moina, Brachionus, Monostyla, Filinia. Cadmium was found to be most toxic and Zinc was least toxic to zooplankton. Ostracods and Cyclops were resistant forms and rotifers were sensitive forms in relation to metallic exposure. Sensitivity pattern observed during laboratory experiments was found to be in accordance with biodiversity variation of zooplankton in different ponds of Berach river system.

Zonal jets and cyclone–anticyclone asymmetry in decaying rotating turbulence: laboratory experiments and numerical simulations

2012 ◽  
Vol 106 (6) ◽  
pp. 557-573 ◽  
Author(s):  
Stefania Espa ◽  
Isabella Bordi ◽  
Thomas Frisius ◽  
Klaus Fraedrich ◽  
Antonio Cenedese ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Laboratory Experiments ◽  
Zonal Jets ◽  
Rotating Turbulence

scholarly journals Dynamics of Convectively Driven Banded Jets in the Laboratory

2007 ◽  
Vol 64 (11) ◽  
pp. 4031-4052 ◽  
Author(s):  
Peter L. Read ◽  
Yasuhiro H. Yamazaki ◽  
Stephen R. Lewis ◽  
Paul D. Williams ◽  
Robin Wordsworth ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Turbulent Flows ◽  
Large Scale ◽  
Zonal Flow ◽  
Inertial Range ◽  
Instability Criterion ◽  
Rossby Wave Breaking ◽  
Outer Planets ◽  
Zonal Jets ◽  
Geostrophic Turbulence

Abstract The banded organization of clouds and zonal winds in the atmospheres of the outer planets has long fascinated observers. Several recent studies in the theory and idealized modeling of geostrophic turbulence have suggested possible explanations for the emergence of such organized patterns, typically involving highly anisotropic exchanges of kinetic energy and vorticity within the dissipationless inertial ranges of turbulent flows dominated (at least at large scales) by ensembles of propagating Rossby waves. The results from an attempt to reproduce such conditions in the laboratory are presented here. Achievement of a distinct inertial range turns out to require an experiment on the largest feasible scale. Deep, rotating convection on small horizontal scales was induced by gently and continuously spraying dense, salty water onto the free surface of the 13-m-diameter cylindrical tank on the Coriolis platform in Grenoble, France. A “planetary vorticity gradient” or “β effect” was obtained by use of a conically sloping bottom and the whole tank rotated at angular speeds up to 0.15 rad s−1. Over a period of several hours, a highly barotropic, zonally banded large-scale flow pattern was seen to emerge with up to 5–6 narrow, alternating, zonally aligned jets across the tank, indicating the development of an anisotropic field of geostrophic turbulence. Using particle image velocimetry (PIV) techniques, zonal jets are shown to have arisen from nonlinear interactions between barotropic eddies on a scale comparable to either a Rhines or “frictional” wavelength, which scales roughly as (β/Urms)−1/2. This resulted in an anisotropic kinetic energy spectrum with a significantly steeper slope with wavenumber k for the zonal flow than for the nonzonal eddies, which largely follows the classical Kolmogorov k−5/3 inertial range. Potential vorticity fields show evidence of Rossby wave breaking and the presence of a “hyperstaircase” with radius, indicating instantaneous flows that are supercritical with respect to the Rayleigh–Kuo instability criterion and in a state of “barotropic adjustment.” The implications of these results are discussed in light of zonal jets observed in planetary atmospheres and, most recently, in the terrestrial oceans.

Coupled CFD-DEM modelling to assess settlement velocity and drag coefficient of microplastics

2020 ◽  
Author(s):  
Robin Jérémy ◽  
Latessa Pablo Gaston ◽  
Manousos Valyrakis
Keyword(s):  
Fluid Dynamics ◽  
Fresh Water ◽  
Turbulent Flows ◽  
Transport Processes ◽  
Water Bodies ◽  
World Health ◽  
Drinking Water Source ◽  
Drag Coefficients ◽  
Wide Range ◽  
The Impact

&lt;p&gt;Several studies have documented high concentration of microplastics on fresh water sources, oceans and even on treated tap and bottled water. Understanding the physics behind these particles in the water environment has become one of the key research needs identified in the World Health Organization Report (2019). In order to develop novel and efficient methodologies for sampling, treating and removing microplastics from water bodies, a thorough understanding of the sources and transportation and storage mechanisms of these particles is required.&lt;/p&gt;&lt;p&gt;In this article, the settlement velocity affecting the transport [1, 2] of low-density particles (1&lt;r&lt;1.4 g.cm&lt;sup&gt;-3&lt;/sup&gt;) and drag coefficients is assessed through numerical modelling. The effects of fluid and particle relative densities and media temperatures are analysed, as well as the impact of the particle size and shapes [3].&lt;/p&gt;&lt;p&gt;Computational Fluid Dynamics (CFD) techniques are applied to solve the fluid dynamics while the Discrete Element Method (DEM) approach is used to model the particle trajectories [4]. These two modules are coupled under the CFDEM module, which transmits the forces from the fluid into the particle and from the particle into the surrounding water through the Fictitious Boundary Method approach.&lt;/p&gt;&lt;p&gt;Several tests are run under the same particle conditions in order to estimate the influence of turbulent flows on these experiments. The influence from different particle densities and diameters on settling velocities and drag coefficients is assessed. The numerical results are validated against a wide range of experimental data [2, 3] and compared against empirical predictions.&lt;/p&gt;&lt;p&gt;There is an urge for gaining a better understanding of the sources and transport of microplastics through fresh water bodies. In this sense, sampling and quantification of microplastics in a drinking water source is key to evaluate the environment status and to design the most appropriate techniques to reduce or remove the microplastics from the aquatic environments. The implementation of coupled CFD-DEM models provides a very powerful tool for the understanding and prediction of the transport processes and the accumulation of microplastics along the fluvial vectors.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;References&lt;/p&gt;&lt;p&gt;[1] Valyrakis M., Diplas P. and Dancey C.L. 2013. Entrainment of coarse particles in turbulent flows: An energy approach. J. Geophys. Res. Earth Surf., Vol. 118, No. 1., pp 42- 53, doi:340210.1029/2012JF002354.&lt;/p&gt;&lt;p&gt;[2] Valyrakis, M., Farhadi, H. 2017. Investigating coarse sediment particles transport using PTV and &amp;#8220;smart-pebbles&amp;#8221; instrumented with inertial sensors, EGU General Assembly 2017, Vienna, Austria, 23-28 April 2017, id. 9980.&lt;/p&gt;&lt;p&gt;[3] Valyrakis, M., J. Kh. Al-Hinai, D. Liu (2018), Transport of floating plastics along a channel with a vegetated riverbank, 12th International Symposium on Ecohydraulics, Tokyo, Japan, August 19-24, 2018, a11_2705647.&lt;/p&gt;&lt;p&gt;[4] Valyrakis M., P. Diplas, C.L. Dancey, and A.O. Celik. 2008. Investigation of evolution of gravel river bed microforms using a simplified Discrete Particle Model, International Conference on Fluvial Hydraulics River Flow 2008, Ismir, Turkey, 03-05 September 2008, 10p.&lt;/p&gt;

An experimental study of the surface elevation probability distribution and statistics of wind-generated waves

1980 ◽  
Vol 101 (1) ◽  
pp. 179-200 ◽  
Author(s):  
Norden E. Huang ◽  
Steven R. Long
Keyword(s):  
Experimental Study ◽  
Probability Density Function ◽  
Probability Distribution ◽  
Wave Field ◽  
Field Data ◽  
Laboratory Experiments ◽  
Laboratory Data ◽  
Surface Elevation ◽  
Strong Wind ◽  
Non Gaussian

Laboratory experiments were conducted to measure the surface elevation probability density function and associated statistical properties for a wind-generated wave field. The laboratory data together with some limited field data were compared. It is found that the skewness of the surface elevation distribution is proportional to the significant slope of the wave field, §, and all the laboratory and field data are best fitted by \[ K_3 = 8\pi\S, \] with § defined as ($(\overline{\zeta^2})^{\frac{1}{2}}/\lambda_0 $, where ζ is the surface elevation, and λ0 is the wavelength of the energy-containing waves. The value of K3 under strong wind could reach unity. Even under these highly non-Gaussian conditions, the distribution can be approximated by a four-term Gram-Charlier expansion. The approximation does not converge uniformly, however. More terms will make the approximation worse.

scholarly journals Rotating gravity currents: small-scale and large-scale laboratory experiments and a geostrophic model

2007 ◽  
Vol 578 ◽  
pp. 35-65 ◽  
Author(s):  
P. J. THOMAS ◽  
P. F. LINDEN
Keyword(s):  
Fresh Water ◽  
Large Scale ◽  
Laboratory Experiments ◽  
Salt Water ◽  
Discharge Rate ◽  
Small Scale ◽  
Data Sets ◽  
Continuous Release ◽  
Dimensional Parameters ◽  
Gravity Driven

Laboratory experiments simulating gravity-driven coastal surface currents produced by estuarine fresh-water discharges into the ocean are discussed. The currents are generated inside a rotating tank filled with salt water by the continuous release of buoyant fresh water from a small source at the fluid surface. The height, the width and the length of the currents are studied as a function of the background rotation rate, the volumetric discharge rate and the density difference at the source. Two complementary experimental data sets are discussed and compared with each other. One set of experiments was carried out in a tank of diameter 1 m on a small-scale rotating turntable. The second set of experiments was conducted at the large-scale Coriolis Facility (LEGI, Grenoble) which has a tank of diameter 13 m. A simple geostrophic model predicting the current height, width and propagation velocity is developed. The experiments and the model are compared with each other in terms of a set of non-dimensional parameters identified in the theoretical analysis of the problem. These parameters enable the corresponding data of the large-scale and the small-scale experiments to be collapsed onto a single line. Good agreement between the model and the experiments is found.

Scaling, spectra and zonal jets in beta-plane turbulence

2004 ◽  
Vol 16 (7) ◽  
pp. 2592-2603 ◽  
Author(s):  
Sergey Danilov ◽  
David Gurarie
Keyword(s):  
Zonal Jets ◽  
Beta Plane
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