Redondo, J. M.; Vila, M.; Tellez, J-D; Lopez, P.; Sánchez, M. Topical Problems of Fluid Mechanics Vol. 2016, num. 2, p. 169-176 DOI: 10.14311/TPFM.2016.023 Date of publication: 2016-02-10 Journal article
Turbulence affects molecular mixing in a large variety of physical processes both in the
environment, in astrophysics and in industrial situations. In some events it is interesting to
enhance the transport of mass, heat, humidity and pollutants, while sometimes it is
interesting to reduce mixing. Here we analyse some turbulent descriptors which reflect the
mixing processes in the compressible induced instabilities that take place in shocks, such as
Richtmyer-Meshkov and Rayleigh-Taylor (RM and RT). We present results related to both
instabilities and discuss their spatial and temporal variability during the advance of a
mixing front, and also their relationships with other scaling arguments. Two types of
experiments were used in this study: Mixing generated by gravitational acceleration in low
Atwood number incompressible experiments using fluids; and the full compressible shocktube
experiments using interfaces between different density gases. The role of local
turbulence has mostly relied on advanced visualization measurements through multifractal
methods. Comparisons with numerical experiments of shock driven fronts occurring at
density interfaces are also relevant. The global advance of the fronts is also measured and
fractal descriptors are calculated in both Large Eddy Simulation (LES) and Kinematic
Simulation KS models
The detailed study of the turbulence and the fluid flow in sport is an open and exciting field of research, in particular in swimming and aquatic sports there is a wealth of new techniques that may aid performance. In swimming, thanks to measurement techniques like
Particle Image Velocimetry (PIV), Particle Tracking (PT) or pattern analysis, now it is possible to measure the flow environment and not just the human movement. Numerical Computational Fluid Dynamics (CFD) is also a useful tool. We present several techniques stressing the importance of 3D effects and the dynamics of enhanced propulsion by hands and feet while the reduction in resistance need to be considered in an integrated way.
Examples of Sculling, Hand wakes, Underwater Undulatory Swimming (UUS) and Vortex Filament Analysis (VFA) are all interesting to improve swimming techniques.
Turbulent transfer is one of the most important processes in the Atmospheric Boundary Layer (ABL), showing many difficulties in stable situations (SBL): non stationary
conditions, presence of internal gravity waves, intermittency, decoupling from the surface fluxes, etc.
• The Monin-Obukhov (M-O) Theory is a suitable framework for presenting micrometeorological data, as well as for extrapolating and predicting certain micrometeorological
information where direct measurements are not available.
• In order to describe the surface fluxes, which is a key parameter in the atmospheric and dispersion models, the universal similarity functions fm and fh for non dimensional
wind and temperature profiles must be determined .
• Some commonly used linear universal functions can be not valid for moderate to strong stability, leading to important errors in the evaluation of surface fluxes. What is the
range of validity?
Comments to PDF variation and vorticity-helicity evaluation to experiments that show new results from the spectral analyses of the flows in two experiments where turbulent flows were generated in a rotating tank with a topographic ß-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.
In the Edited paper, a turbulent ocean is modelled in the laboratory. The rotation of the Earth around its axis is represented by the rotation of a turntable. Similar to that in the Earth's ocean, the currents in the laboratory "ocean" are created by density effects when the water is heated or made salty. The laboratory currents are measured by a system which is not unlike the satellite altimetry system used by oceanographers to create "topographic" maps of the elevation of the water surface.
The effect of the differences between Salt and Heat agents to stratify the flow are discussed stressing the Rossby deformation scale, which marks where and when the rotation
induced Coriolis forces are in equilibrium with the effect of buoyancy. The upscale transfer of energy is inhibited at the Rossby deformation scale by baroclynic instability
at larger scales, which accounts for the dominant observed sizeof geophysical vortices.
Different regions of the parameter space based on the local versions of the Reynolds number, the Richardson number and the Rossby number should also be used to compare both laboratory observations and field data as well as the different experiments between themselves
Editor comments at Non linear Processes in Geophysics of the paper: Complex environmental ß-plane turbulence: laboratory experiments with altimetric imaging velocimetry of the Special Issue Complex Environmental and Geophysical Turbulence by
A. M. Matulka et al.
In the Edited paper, a turbulent ocean is modelled in the laboratory. The rotation of the Earth around its axis is represented by the rotation of a turntable. Similar to that in the Earth's ocean, the currents in the laboratory
New industrial and didactic flow solutions based on new flow concepts are needed to meet the unprecedented requirements set by the dramatically increasing energy needs, the use of Thermoelectric didactive devices are neded for better environmental and industrial performance. We need improvements to existing solutions, such as better convective control with radical new developments thanks to thermoelectricity coupled with fluid dynamics descriptors such as PIV. also energy savings and reduction of adverse environmental impacts can come from multifractal concepts. The development of new flows both numerically and experimentally are important for solutions with fully resolved simulations because existing turbulence models cannot be applied indiscriminately on many untested new flow ideas.
One very recent example is the turbulent flows generated by fractal grids. Fractal grids are made from a structure, such as a square, repeated at different scales that allow higher mixing efficiencies.
We present several experimental studies on Turbulent Mixing produced by the advance of a density interface produced by brine when an oscilating grid produces zero-mean turbulence at a certain vertical distance. The older regular grid experiments have been re-calibrated and compared with fractal grids of different solidity and self-similar characteristics. Recent PIV and advanced visualizations will be compared with the initial work performed in 1993.
Pastore, N.; Cherubini, C.; Gassi, C.; Allegretti, N.; Redondo, J. M.; Tarquis Alfonso, A. Energy procedia Vol. 76, p. 273-281 DOI: 10.1016/j.egypro.2015.07.860 Date of publication: 2015-07-01 Journal article
Fractured rocks play an important role in transport of natural resources through subsurface systems. In recent years, interest has
grown in investigating heat transport by means of tracer tests, driven by the important current development of geothermal
applications. Many field and laboratory tracer tests in fractured media show that fracture - matrix exchange is more significant
for heat than mass tracers, thus thermal breakthrough curves are strongly controlled by matrix thermal diffusivity. In this study,
the behaviour of heat transport in a fractured network, at bench laboratory scale, has been investigated.
The UPC at the Vilanova i la Geltru Campus and UPC- CIMNE at Castelldefels will host the ERCOFTAC international summer school on Complex Environmental Turbulent Flows. This follows similar events organized in Vilanova, Madrid, Warsav, Prague, Volos and Barcelona since 1992. The main motivation for this 2015 Summer School is to study in depth Transport and diffusion in non-homogeneous, non-isotropic and non-stationary turbulence mostly affected by body forces, which is typical of Environmental Flows. Magnetic fields, Stratification and Rotation are fundamental processes afecting turbulence in industrial and environmental flows, for example to predict convective heat transport, pollutant diffusion and mixing. Reactions, solute transport in Environmental Fuid Dynamics, direct and inverse cascades in turbulence at different scales will be discussed with related topics. The experimental part of the summer school and a series of student presentations will be done at the ERCOFTAC PAN-EUROPEAN LABORATORY ON NON-HOMOGENEOUS TURBULENCE with a one day dedicated Workshop during the summer school. (2 July).
Mixing generated by gravitational acceleration and the role of local turbulence measured through
multifractal methods is examined in numerical experiments of Rayleigh-Taylor and Richtmyer-Meshkov driven
front occurring at density interfaces. The global advance of the fronts is compared with laboratory experiments
and Nusselt and Sherwood numbers are calculated in both large eddy simulation (LES) and kinematic simulation
KS models. In this experimental method, the mixing processes are generated by the evolution of a discrete set of forced
turbulent plumes. We describe the corresponding qualitative results and the quantitative conclusions based on measures of the
density field and of the height of the fluid layers. We present an experimental analysis to characterize the partial mixing process.
The conclusions of this analysis are related to the mixing efficiency and the height of the final mixed layer as functions
of the Atwood number, which ranges from 9.8×10-3 to 1.34×10-1
Costal Eddy Structure and Pollution Detection from SAR Spectral Analysis
Jose Manuel Redondo1,3, Juan Jose Martinez Benjamin1, Margarita Diez2,3, Pilar Lopez Gonzalez-Nieto4, Juan Jorge3, Jackson Tellez3
1ETSEB UPC Barcelona Tech, Spain; 2Ports de la Generalitat, Vilanova i la Geltru, Barcelona 08800, Spain; 3ETSECCPB, Universitat Politecnica de Catalunya, Dept. Fisica Aplicada, Barcelona, Spain; 4IPD, Univ. Complutense Madrid, Madrid, Spain.
Remote sensing by advanced radar active and passive methods provide better discrimination and higher resolution in complex geophysical flows. In the ocean, and even more so, in the coastal zone,where turbulent flow is generated in the ocear surface either by waves, wind or/and local currents. The conditions of the medium are highly non-homogeneous, and in the presence of a pollutant the SAR detects many topological features[1,2]. New techniques are used for the subsequent analysis, of more than 2000 Images provided by the ESA ERS1/2, ASAR, ENVISAT, RADARSAT and with additional cruise observations and measurements [4-9] in the North-west Mediterranean Sea area between 1996 and 2012.
Also the structure of the flows are presented using self-similar traces that may be used to parametrize mixing at both limits of the Rossby Deformation Radius scale. RL Results show the ability to identify different SAR signatures may predicting the self-similar structure of the turbulence[3,4], complex coastal field-dependent behavior is strongly influenced by stratification and rotation of the turbulence spectrum is observed only in the range smaler than local RL. The measures of diffusivity from buoy or tracer experiments are used to calibrate the behaviour of different tracers and pollutants, both natural and man-made in the NW Mediterranean Sea [4,5]. Thanks to different polarization and intensity levels in satellite imagery can be used to distinguish between natural and man-made sea surface features due to their distinct self-similar and fractal as a function of spill parameters, environmental conditions and history of both oil release and weather conditions.
Environmental factors determine [6,7] spreading. On the other hand helical and stratified turbulence is also modified by the intermittency and by the maximum fractal dimension, [5,8], which is related to the energy spectrum of the flow.
 Redondo, J.; Matulka, A.M.; Carrillo, J. (2010) Vortex decay in stratified flows. Topical Problems of Fluid Mechanics 2010. Praga, AS. pp. 127-130.
 Castilla R., Redondo J.M., Gamez P.J. and Babiano A. (2007), Non Linear Processes in Geophysics, 14, (2007) pp. 139.
 J. M. Redondo, J. H. Fernando and S. Pares (1995) Cloud entrainment by internal or
external turbulence, Mixing in geophysical flows, J. M. Redondo and O. Metais (Eds), CIMNE, Barcelona (1995) pp. 379-392.
 Platonov A., Carillo A., Matulka A., Sekula E., Grau J., Redondo J. M., Tarquis A. M. (2008) Multifractal observations of eddies, oil spills and natural slicks in the ocean surface", Il Nuovo Cimento, Vol. 31 C, N. 5-6, pp. 861-880.
 Redondo J.M. (1996) Vertical microstructure and mixing in stratified flows. Advances in Turbulence VI. Eds. S. Gavrilakis et al.(1996), pp. 605-608.
[7,8] Nicolleau, F.C.G.A.; Cambon, C.; Redondo, J.M.; Vassilicos, J.C.; Reeks, M.; Nowakowski, A.F. (Eds.)(2011) New Approaches in Modeling Multiphase Flows and Dispersion in Turbulence, Fractal Methods and Synthetic Turbulence. ERCOFTAC Serie
 Fraunie P., Berreba S. Chashechkin Yu.D., Velasco D. and Redondo J.M. (2008) Large eddy simulation and laboratory experiments on the decay of grid wakes in strongly stratified flows. Il Nuovo Cimento C 31, 909-930.
 Matulka, A., López, P., Redondo, J. M., and Tarquis, A.(2014) On the entrainment coefficient in a forced plume: quantitative effects of source parameters, Nonlin. Processes Geophys., 21, 269-278.
Pastore, N.; Chierubini, C.; Giassi, C.; Allegretti, N.; Redondo, J. M.; Tarquis Alfonso, A. European Geosciences Union General Assembly p. 2279- Presentation's date: 2015-04-17 Presentation of work at congresses
Fractured rocks play an important role in transport of natural resources or contaminants transport through
subsurface systems. In recent years, interest has grown in investigating heat transport by means of tracer tests,
driven by the important current development of geothermal applications. In literature different methods are
available for predicting thermal breakthrough in fractured reservoirs based on the information coming from tracer
An important achievement is the invention and development of techniques for measurement of velocities in hydraulic engineering
Knowledge of the technological advances in digital cameras with high
resolution and high speed are extremely useful to measure relevant predictive parameters in the environment. Here we present some
advances in image processing techniques, these can be used in hydraulic hazard predictions therefore, providing a tremendous potential to measure the behavior of the water surface flow.
This technique was performed at the Laboratory of Hydraulics Department of Hydraulic, Maritime and Environmental Universidad Pol
ytechnic de Catalonia, (UPC Barcelona Tech) where we used a
water flow platform with dimensions of 5.5 m long and 4 m wide allowing a zone of useful measurements of 5.5m x 3m, where the width is similar of a typical urban road. The platform allows to modify the slopes longitudinal at angles between 0% and 10% and transversal slopes of between 0% and 4%. And there is also the possibility of a range of flows. In the experiments discussed here we used flow rates up to 200 l/s
In addition, a camera high resolution 1280 x 1024 pixels with maximum speed of 488 frames per second.
A novel technique using particle image velocimetry to measure surface flow velocities has been developed and validated with the
experiments assays with the grate inlets.
In this case, the Methodology carried out can become a useful tools to understand the hydraulics behavior of the flow approaching the inlet where the traditional measuring equipment have serious problems and limitations.
We study at several non-homogeneous sites, such as the coastal Mediterranean Area (Ebro Delta, Blanes) and in
the iberian Plateau the wind intermittency as well as the fractal structure of the induced cloud and wave fronts.
Weather data from 10 and 100m hight masts are used to calculate Local Richardson number, Monin-Obukhov
length, eddy transfer coefficients, turbulent kinetic energy, turbulent intensities, friction velocities and sensible heat flux at three levels (5, 17 and 32 m) were considered. The results show how the stability at 17 and 32 minfluences the turbulent transfer near the ground.
The shear of wind or convection are the main mechanism to produce mixing in the surface, which is often detected in satellite images of nearby clouds or coastal features.
The influence of internal gravity-waves on the atmospheric boundary-layer during strong stable stratification is quantified
Redondo, J. M.; Tellez, J-D; Sotillos, L.; Lopez, P.; Furmanek, P.; Sánchez, J.; Diez, M. European Geosciences Union General Assembly p. 1-2 Presentation's date: 2015-04-14 Presentation of work at congresses
Local Diffusion and the topological structure of vorticity and velocity fields is measured in the transition from a homogeneous linearly stratified fluid to a cellular or layered structure by means of convective cooling and/or heating[1,2]. Patterns arise by setting up a convective flow generated by an array of Thermoelectric devices (Peltier/Seebeck cells) these are controlled by thermal PID generating a buoyant heat flux . The experiments described here investigate high Prandtl number mixing using brine and fresh water in order to form density interfaces and low Prandtl number mixing with temperature gradients. The set of dimensionless parameters define conditions of numeric and small scale laboratory modeling of environmental flows. Fields of velocity, density and their gradients were computed and visualized [3,4]. When convective heating and cooling takes place the combination of internal waves and buoyant turbulence is much more complicated if the Rayleigh and Reynolds numbers are high in order to study entrainment and mixing. Using ESS and selfsimilarity structures in the velocity and vorticity fieds and intermittency [3,5] that forms in the non-homogeneous flow is related to mixing and stiring. The evolution of the mixing fronts are compared and the topological characteristics of the merging of plumes and jets in different configurations presenting detailed comparison of the evolution of RM and RT, Jets and Plumes in overall mixing. The relation between structure functions, fractal analysis and spectral analysis can be very useful to determine the evolution of scales. Experimental and numerical results on the advance of a mixing or nonmixing front occurring at a density interface due to body forces and gravitational acceleration are analyzed considering the fractal and spectral structure of the fronts like in removable plate experiments for Rayleigh-Taylor flows. The evolution of the turbulent mixing layer and its complex configuration is studied taking into account the dependence on the initial modes at the early stages and its spectral, self-similar information [3,7-9]. Spectral and Fractal analysis on the images has been used in order to estimate dominant mixing structures as well as the dispersion relations of basic instabilities [4,8. Comparison of the range of entrainment values from laboratory experiments with those ocurring in nature, both in the atmosphere and ocean or in Astrophysics shows the importance of modeling correctly the integral lengthscales of the turbulence. The Entrainment may actually be related to the ratio of the flux to gradient Richardson numbers as well as the Turbulent Schmidt or Prandtl number [6,8] and their structure functions . Turbulent mixing diagnostics are based on schlieren and shadowgraph visualization, planar laser sheet, laser Doppler velocimetry (LDV) and particle image velocimetry (PIV). We are interested by the influence of initial conditions (flux gradients of various sizes) on the transition to turbulent mixing, the influence of subsequent vortices and waves, initially in a one dimensional or plane configuration and furthermore in a two-three dimensional configuration with the interface oblique with respect to the horizontal.
Numeric modeling of a flow past vertical and horizontal strips towed in a linearly stratified tank are preformed by comparison to laboratory experiments using Schlieren visualization, density marker and probe measurements of internal wave fields. Both parts of the wave fields including upstream transient and downstream stationary waves were resolved. Analysis is here focusing on observed near wake singular components.
Experimental results in order to map the different transitions between two and three dimensional convection in an enclosure with complex driven heat flows. The size of the water tank is of 0.2 x 0.2x 0.1 m and the heat sources or sinks can be regulated both in power and sign [1-3]. The thermal convective driven flows are generated by Seebeck and Peltier effects in two opossed walls, thus generating different types of convective cells that varies strongly with the Topology of the boundary conditions as a function of Rayleigh, Peclet and Nusselt numbers,[4-6] Visualizations are performed by PIV, Particle tracking and shadowgraph.
Diffusion is measured in the transition from a homogeneous linearly stratified fluid to a cellular or layered structure by means of convective stirring. Patterns arise by setting up a convective flow generated by a buoyant heat flux . The experiments described here investigate high Prandtl number mixing using brine and fresh water in order to form density interfaces and low Prandtl number mixing with temperature gradients .
We also present a detailed comparison of the evolution of Jets and Plumes in overall mixing. The relation between fractal analysis and spectral analysis can be very useful to determine the evolution of scales. Experimental and numerical results on the convective cells are compared with Remote Sensing observations of the atmosphere, SAR images of the ocean can detect well these types of structures over the ocean[5-7].
The evolution of the turbulent mixing layer and its complex configuration is studied taking into account the dependence on the initial modes at the early stages and its spectral, self-similar information . Spectral and Fractal analysis on the images has been used in order to estimate dominant mixing structures as well as the dispersion relations of basic instabilities .
This Lecture notes are designed to complement the class notes of the course Turbulence and Mixing and Ocean Turbulence prsented at UPC, Toulon University and the Campus Universitary de la Mediterrania since 2010. It draws from Wikipedia and basic student support webs the pre-requisite knowledge on basic principles of Physics used in the Turbulence course. The main enphasis is on the use of clasical dynamics notations and thermodynamics which are not usually presented in engineering courses. It concentrates on the turbulence aspects related to energy, Entropy and scaling of the complex aspects of environmental turbulence. The use and explanation of Feynman diagrams in turbulence is also seldom presented away from quantum mechanics so the intention of these notes is also to show the synergy between different branches of physics and engineering.
A compilation of mathematical techniques and physical basic knowledge in order to prepare the post graduate students of the subjects of physical geodesy, environmental physics and the visiting students of Erasmus-Socrates projects of the Mediterranean Institute of Oceanography of Toulon and the Campus Universitari de la Mediterrania in Vilanova i la Geltru, Barcelona.
Experimental results on mixing occurring at a convective driven
or a overturning density gradient due to gravitational acceleration are
analyzed considering the velocity field of the process. We present
a thermoelectric driven heating and cooling experimental device in
order to investigate the different motions between two dimensional
convection in an enclosure and the 3 D complex flows. The size of the
enclosure is of 0.2 x 0.2 x 0.1 m and the heat sources or sinks (two
in facing walls) can be regulated both in power and sign (Redondo
1992). The thermal convective driven flows are generated by Seebeck
and Peltier effects  in 4 wall extended positions of 0.05 x 0.05 cm
each. The parameter range of convective cell array varies strongly
with the Topology of the Boundary conditions. At present side heat
fluxes are considered and estimated as a function of Rayleigh, Peclet
and Nusselt numbers, but the tilting possibilities of the BEROTZA
built experimental device also allow to heat/cool at top and bottom
at different angles
This contribution presents an experimental investigation on the behaviour of sediments
in a turbulent boundary layer flow, it compares the energy and vorticity needed to generate
a turbidity current and the zero mean flow lift off and entrainment across a stably stratified
density interface, either produced by solutes, sediment concentration or both. The
experimental parameters are used to quantify the entrainment, the mixing efficiency and
different types of dominant instability and the topological aspects of the turbulent cascade
in the environment. The experiments allow to detected both horizontally and vertically.
The local sediment and velocity fields. Grid turbulence in an enclosed two layer system
is measured with PIV as well as with sonic velocimetry. Observations of the horizontal
and vertical velocity energy spectra as well as the structure functions are used to estimate
local mixedness, entrainment and intermittency.
Turbulence affects the dynamics and the evolution of the turbulent mixing layer and its complex configuration is studied taking into account the dependence on the initial modes at the early stages and its spectral, self-similar information. Most models of the turbulent mixing evolution generated by hydrodynamics instabilities do not include any dependence on initial conditions, but in many relevant physical problems this dependence is very important, for instance, in Inertial Confinement Fusion target implosion. We discuss simple initial conditions with the aid of a numerical model developed at FIAN Lebedev which was compared with results of many simulations. The analysis of Kelvin-Helmholtz, Rayleigh-Taylor, Richtmyer-Meshkov and of accelerated instabilities is presented locally, and seen to dominate the turbulent cascade mixing zone differently under different initial conditions. Simulations and multi-fractal and neuron network analysis of Turbulent Mixing under RT and RM instabilities are presented for the different experiments and numerical simulations, further analysis on the numerical model is presented using wavelet preprocessing of the simulation results and neuron network presentation of the data. The aspect ratios of the bubble induced convective cells are seen to depend on the boundary and initial conditions applied to the front. The evolution of the Rayleigh-Taylor instability develops into a turbulent mixing front that may be investigated further using the information that the fractal dimensions or Kolmogorov Capacities give as the flow evolves in time. The basic self-similar characteristics of the flow are compared and the evolution of the multi-fractal dimensions of density, velocity and vorticity contours provides indication that most mixing takes place at the sides of the dominant convective blobs. In the context of determining the influence of structure on mixing ability and determine the regions of the front which contribute most to molecular mixing.
The present study compares the performances and reliabilities of the classical Mobile – Immobile Model (MIM)
and the Explicit Network Model (ENM) that takes expressly into account the network geometry for describing
tracer transport behaviour in a fractured sample at bench scale. Though ENM shows better fitting results than
MIM, the latter remains still valid as it proves to describe the observed curves quite well.
The results show that the presence of nonlinear flow plays an important role in the behaviour of solute
transport. Firstly the distribution of solute according to different pathways is not constant but it is related to the
flow rate. Secondly nonlinear flow influences advection, in that it leads to a delay in solute transport respect to the
linear flow assumption. Whereas nonlinear flow does not show to be related with dispersion. The experimental
results show that in the study case the geometrical dispersion dominates the Taylor dispersion. However the
interpretation with the ENM model shows a weak transitional regime from geometrical dispersion to Taylor
dispersion for high flow rates.
The improvements in experimental methods and high resolution image analysis are nowadays able to detect subtle
changes in the structure of the turbulence over a wide range of temporal and spatial scales, we compare the
scaling shown by different mixing fronts driven by buoyancy that form a Rayleigh-Taylor mixing front. We use
PIV and density front tracking in several experimental configurations akin to geophysical overturning . We
parametrize the role of unstable stratification by means of the Atwood number and compare both the scaling and
the multifractal and the maximum local fractal structure functions of the different markers used to visualize the
front. Both reactive and passive scalar tracers are used to investigate the mixing structure and the intermittency
of the flow. Different initial conditions are compared and the mixing efficiency of the overal turbulent processes
The behavior of a forced plume is mainly controlled by the source buoyancy and momentum fluxes and the efficiency of turbulent mixing between the plume and the ambient fluid (stratified or not). The interaction between the plume and the ambient fluid controls the plume dynamics and is usually represented by the entrainment coefficient aE. Commonly used one-dimensional models incorporating a constant entrainment coefficient are fundamental and very useful for predictions in geophysical flows and industrial situations. Nevertheless, if the basic geometry of the flow changes, or the type of source or the environmental fluid conditions (e.g., level of turbulence, shear, ambient stratification, presence of internal waves), new models allowing for variable entrainment are necessary. The presented paper is an experimental study based on a set of turbulent plume experiments in a calm unstratified ambient fluid under different source conditions (represented by different buoyancy and momentum fluxes). The main result is that the entrainment coefficient is not a constant and clearly varies in time within the same plume independently of the buoyancy and the source position. This paper also analyzes the influence of the source conditions on the mentioned time evolution. The measured entrainment coefficient aE has considerable variability. It ranges between 0.26 and 0.9 for variable Atwood number experiments and between 0.16 and 0.55 for variable source position experiments. As is observed, values are greater than the traditional standard value of Morton et al. (1956) for plumes and jets, which is about 0.13
We present a detailled experimental study of the thermocapillary motion of an aniline drop in an stably stratified fluid sytem driven by a laser beam. The thermocapillary motion of drops is the result of the temperature dependence of the interfacial tension. If the surface of the drop is subject to thermal gradients, then non-equilibrium surface tension effects appear, which in some cases can move the drop. We measure some of the velocity induced fields , vorticity, oscilations and intermittency of this complex flow. The source of the no uniformity of the temperature of the surface can be, as is in this experiment, the non uniform heating of the floating drop by a laser beam. In recent years, the thermocapillary movement of bubbles and drops under the influence of laser radiation has received more experimental attention thanks to the improvement in the flow visualization techniques.
We present a versatile apparatus that allows students to understand, manipulate and measure many aspects of buoyancy driven convective flows. The basic prototype presented and described in this brochure is a sturdy and simple to use laboratory or demonstration lecture equipment.
It consists of a visualization optimized Perspex enclosure of plane area 200mmx 200 mm and 100 mm thickness. Four thermoelectric Peltier effect coolers/heaters are used to generate different types of convective flows, both in steady state situations and in transients. The flow visualization patterns and techniques that are provided and may be used with ease will upgrade your student laboratory to the XXI st century.
Here we show the technical details of the experimental apparatus and show some examples of its use in several disciplines.
Tarquis Alfonso, A.; Platonov, A.; Matulka, A.M.; Grau, J.; Sekula, E.; Diez, M.; Redondo, J. M. Nonlinear processes in geophysics Vol. 21, num. 2, p. 439-450 DOI: 10.5194/npg-21-439-2014 Date of publication: 2014-01-01 Journal article
The use of synthetic aperture radar (SAR) to investigate the ocean surface provides a wealth of useful information that is very seldom used to its full potential. Here we will discuss the application of multifractal techniques to detect oil spills and the dynamic state of the sea regarding turbulent diffusion. We present different techniques in order to relate the shape of the multifractal spectral functions and the maximum fractal dimension to the behaviour of the ocean surface. We compare eddy and sheared dominated flows with convective driven flows and discuss the different features and observation methods. We also compare the scaling of different oil spills detected by means of SAR images. Recent spills and weathered ones are selected and compared to investigate their behaviour in different spatial and temporal ranges. We calculate the partition function based on the grey intensity value of each SAR pixel deriving several types of multifractal spectra as a function of spill residence time estimated for each image. Image manipulations are seen to reduce the speckle noise and thus distinguish much better the texture of the oil spill images. The results are used to discuss how eddy diffusivity may be estimated and used in a description of the ocean surface using a simple turbulence kinematic simulation model to predict the shape of oil spills. Differences in the multifractal spectrum among SAR images may detect the slicks due to plankton and also provide information on the age of the oil spills, on the Lagrangian turbulent structure and on ocean surface diffusivity.
The study of particle diffusion and of turbulent sedimentation is of great importance in many geophysical fields, such as in Environmental Science or Oceanography as well as in Bio-environmental and industrial processes. For a long time, the study of diffusion was numerically computed with random free paths, which gives Brownian behavior.
These stochastics methods have the objection that do not take into account the flow profile. On the other hand, there are many ways to simulate a fluid flow, but when this is turbulent our aim is to simulate the behaviour of neutral or heavy and inertial particles of biological or geological nature in a turbulent flow, in a simple way with a kinematically simulated model and to validate the results. We use the Kinematic Simulation (KS) model, also known as Synthetic Turbulence to model several environmental situations, both in the Atmosphere and the Ocean.
We calculate diffusion and scaling of the velocity and vorticity in a thermoelectric driven heating and cooling experimental device in order to map the different transitions between two and three dimensional convection in an
enclosure and complex driven flows. The size of the water tank is of 0.2 x 0.2 x 0.1 m and the heat sources or sinks can be regulated both in power and sign. The thermal convective driven flows are generated by Seebeck
and Peltier effects in 4 wall extended positions of 0.05 x 0.05 cm each. The parameter range of convective cell array varies strongly with the Topology of the boundary conditions. At present side heat fluxes are considered
and estimated as a function of Rayleigh, Peclet and Nusselt numbers, Visualizations are performed by PIV, Particle tracking and shadowgraph using the DigiFlow fluid visualization programme.
We present a description and some applications of the basic relationships that may affect the figure of merit in complex multiscale thermoelectric materials.
The success of Onsager’s Linear relationships between Fluxes and Forces in explaining the reversible Thermoelectric effects and in deriving Kelvin’s relationships (Onsager 1931) has been extended to include Magneto-Thermo- Electrical effects. Nerst or Nerst-Ettinghausen Effects, among others provide further examples of possible applications in thermal technologies.
The way in which the material structure is built with a controllable multifractal aspect, alternating at many different scales the grains which, either due to intrinsic cristaline anisotropy or due to a selective doping produce power relationships between the interfacial line lengths and the areas in 2D, or beween the area of the surface separating subsets of different material properties and the volumes of the respective grains in 3D. The application of these fractal aspects in order to describe fluxes that may be very different when measured at different scales may also be stated in terms of the relationships between fluxes and forces or between fluxes per unit area and gradients perpendicular to that same area.
When basic physical properties that are defined in a very different geometrical way, such as masic properties or surface properties, the need of integrating over all possible scales arises in order to avoid singularities in the theory. The effect of minimum and maximum grain size clusters and their geometrical self similarity is studied in terms of non-linear relationships and of higher order cumulants for several of the Magneto-Thermo-Electric (Devies 1952) and Thermo-electric Effects
In this Chapter we report on an experimental study of the thermocapillary motion of an aniline drop in an stably stratified fluid system and driven by a laser beam. The thermocapillary motion of drops is the result of the temperature dependence of the interfacial tension. If the surface of the drop is not isothermal gradients of the surface tension appear, which in some cases can move the drop. The source of the no uniformity of the temperature of the surface can be, in particular, the heating of the drop by a laser beam. In the last years, the thermocapillary movement of bubbles and drops under the influence of laser radiation was studied theoretically and experimentally. However, in the literature there is no data on observation of the movement of a single drop in a laser beam. In this paper an experimental methodology is proposed to study such a motion of a drop.
We present scaling applications of coastal SAR images in the NW Mediterranean Sea. The distribution of meso-scale vortices of size, related to the Talwegs, to the local Rossby deformation scale and other dominant features can be used to distinguish dinamical features in the ocean surface. Multi-fractal analysis is then very usefull. The SAR images exhibited a large variation of natural features produced by winds, internal waves, the bathymetric distribution, by convection, rain, etc as all of these produce variations in the sea surface roughness so that the topological changes may be studied and classified. An additional unique value that characterizes the overall
spatial fractal dimension of the system is to integrate the multifractal functions for different intensities. Several types of SAR images exhibit also their different structure functions. The flatness or Kurthosis is a statistic parameter which indicates the shape of the pdfs of the SAR intensity, and seems to be a very good indicator of the degree of existing structure; when flatness changes with scale following a potencial law, intermittency is present. Both the multifractal spectra and the distribution of the Flatness function F are found to be useful tools to measure intermittency, when it is applied to the correlations between the different SAR polarizations and to different physical features. Comparisons with the standard multi-fractal formalism also may reveal the importance of anisotropy and non-locality.
Series of flow percolation experiments under gravity were performed in different glass model and real karstic media
samples. We present a multifractal characterization of the experiments in several parametric non-dimensional
flow descriptors. Using the maximum local multifractal dimension as an additional flow indicator. Also experiments
Non laminar flow and transport conditions in fractured and karstified media were performed at Bari.
The investigation on hypothesis of non linear flow and non fickian transport in fractured aquifers led to a
distinction on the different role of channels and microchannels and of the presence of vortices and eddy trapping. The dominance of the elongated channels produced early arrival times, with the solute traveling along the high velocity channel network. On the other hand in a lumped structured karstic media, the percolation flow produced long tails with local Eddy mixing, entrapment in eddies, and slow flow out of the eddies.
The Synthetic Aperture Radar (SAR) is a useful tool to study both marine water dynamics and its pollution,
this is relevant near the coastline, where river pollution may be also important. Oil spills and natural slicks are
detected with SAR to reveal river and vessel pollution as well as the complex eddy and current interaction
in the ocean surface near the coastline. In the framework of the ESA and European Union contracts, more than
1000 SAR images of the North-west Mediterranean Sea area taken between December 1996 and December
2008 are presented using self-similar traces that may be used to parametrize mixing at both limits of the Rossby
Deformation Radius scale. Results show the ability to identify different SAR signatures and at the same time
provide calibrations for the different
local configurations of vortices, spirals, oil spills and tensioactive slicks that eventually allow predicting the
behaviour of different tracers and pollutants in the NW Mediterranean Sea.
Experimental and theoretical results on the propulsion of swimrners are presented with an
emphasis on the specific characteristics of the wakes produced by the swimmers in the
water. We introduce the subject revising sorne of the previous work on the fruitless
controversy between Drag and Lift cornponents of the forces induced by swirnmers hands.
After presenting sorne experimental results on Underwater Oscillatory Swimrning we
discuss in detail the complex nature of the swimrners body, feet and hand wakes and show
the role of vortices. Severa! basic recornmendations rnay be deduced comparing animal and
human swimming. One is the need to reduce Strouhal numbers to increase propulsion, the
other one is to generate wakes that maximize momenturn and rninimize energy, this is
di scussed in terms of the fluid topological properties of basic vortical flow configurations.
Lopez, P.; Matulka, A.M.; Redondo, J. M.; Tarquis Alfonso, A. International workshop on nonlinear processes in oceanic and atmospheric flows p. 57-59 Presentation's date: 2012-06-01 Presentation of work at congresses
Turbulent plumes are fluid motions whose primary source of kinetic energy and momentum flux is body forces derived from density inhomogeneities. The plume boundary acts as a phase boundary across which ambient fluid is entrained. The difference between the plume-fluid radial velocity and the total fluid velocity quantifies in a natural way the purely horizontal entrainment flux of ambient fluid into the plume across the phase boundary at the plume edge.
At geophysics, it is usual the generation of turbulent plumes as a part of a dispersion process. For example, there are eruptionc plumes, river plumes (into a lake, sea or ocean), mantle plumes, hydrothermal plumes or contaminant plumes, for example. They also are important in engineering (building ventilation processes).
En nuestra sociedad los derivados del petróleo son la fuente principal de energía. Los accidentes con hidrocarburos han
protagonizado episodios de contaminación trágicos para la biosfera del océano. Se analizan algunos de ellos, sus efectos y
sistemas de limpieza.
La complejidad de los procesos físicos, químicos o biológicos que actúan sobre el crudo en el mar, hacen difícil su estudio
en laboratorio. Para ello se hacen numerosas campañas de campo con distintas escalas y procesos físicos predominantes
diferentes: zonas costeras (Delta del Ebro y playa de Vilanova); en aguas confinadas (puerto de Barcelona y puerto de
Recife); y en aguas abiertas (Mediterráneo Occidental), con diferentes tecnologías (foto, vídeo, satélite), para seguir
trazadores eularianos (manchas de leche y fluoresceína, flotantes o hidrocarburos) y lagrangianos (boyas lastradas), se
miden los agentes forzadores: viento, oleaje, marea, etc. y se correlacionan para caracterizar los diferentes escenarios.
También se revisa el estado del arte.
El tratamiento digital de imágenes de vídeo permite numerosas aplicaciones en el campo de la hidromorfodinámica, pues
es posible controlar la evolución espacial y temporal de cualquier parámetro con evidencias visibles y es una técnica no
intrusiva que ofrece datos de oleaje de una zona, en contraposición a los datos puntuales de los sensores. Las imágenes
sufren numerosas alteraciones, deformaciones, ruidos, etc., que hay que depurar previamente.
Los coeficientes de difusión presentan una gran variedad condicionada a la dependencia característica con la escala
temporal y espacial de los fenómenos predominantes. Los coeficientes de difusión medidos se agruparon según el
número de Reynolds y se hizo una clasificación: hipodifusividad, hiperdifusividad y difusión anómala. Esta caracterización de
escenarios permite parametrizar el medio para modelizar su comportamiento y poder predecir su evolución.
En el campo del oleaje se pueden obtener espectros de energía y otros parámetros para su caracterización, detectar la
morfología de barras sumergidas, identificar corrientes de retorno, caracterizar run-up, etc. En el puerto de Barcelona se
tomaron numerosos datos de velocidades de viento (Vv) y corriente (Vc) llegando a una buena correlación entre ambas (Vcx
(cm/s)= 2.306 Vvx (m/s)+ 0.148) y constatando que hay una influencia de otros efectos como la marea, reflexión de los
muelles o difracción que no se pueden obviar.
Las imágenes de Rádar de Apertura sintética SAR permiten detectar episodios de contaminación y analizar la vorticidad a
gran escala del medio. Resultó sorprendente el gran número de manchas detectadas. Se comprobó que los vertidos
siguen la Ley de Zipp (distribución hiperbólica entre los accidentes y su tamaño). Se vió que los remolinos siguen la
dirección de los cañones submarinos. Con el análisis fractal y multifractal del contorno de la mancha se puede caracterizar
su origen (antropogénico o natural como masas de plankton) y su envejecimiento o persistencia, etc. Se comprueba que es
posible que la intermitencia de la turbulencia pueda parametrizarse mediante medidas fractales y que el uso de momentos
de orden superior ayuda a comparar medidas de difusión a distintas escalas mediante la Ley de Richardson Generalizada.
Así se relaciona la pendiente del espectro, la intermitencia y la dependencia temporal de la difusión efectiva.
Los distintos agentes que producen difusión en el mar sufren interacciones no-lineales complejas. Con todo ello, se
pretende contribuir a comprender mejor los procesos de dispersión de los contaminantes en el mar y, por consiguiente,
ayudar en la lucha contra este fenómeno.
In our society the derivatives of petroleum are the main source of energy. The accidents with hydrocarbons have carried out
tragic episodes of contamination for the biosphere of the ocean. Some of them, their effects and systems of cleaning are
The complexity of the physical, chemical or biological processes that act on the oil in the sea, makes their study in laboratory
difficult. For it numerous campaigns of field with different scales and different predominant physical processes become:
coastal zones (Delta of the Ebro and beach of Vilanova); in confined waters (port of Barcelona and port of Recife); and in open
waters (West Mediterranean), with different technologies (photo, video, satellite), to follow Lagrangian tracers (milk spots and
fluoresceine, floating or hydrocarbons) and Euler tracers (ballasted buoys), to measure the agents: wind, waves, tide, etc.
and they are correlated to characterize the different scenes. Also the state-of-the-art is reviewed.
Treatment digital of images of video allows many applications in field of hydromorfodynamics, because it is possible to
control the space and temporary evolution of any parameter with visible evidences and is a nonintrusive technique that offers
data of a zone, in contrast to the pointing data of the sensors. The images put up with numerous alterations, deformations,
noises, etc., that have to purify previously.
The diffusion coefficients present/display a great conditional variety to the dependency characteristic with the temporary and
space scale of the main phenomena. The measured coefficients of diffusion were grouped according to the Reynolds
number and a classification became: hypo-diffusion, hyper-diffusion and anomalous diffusion. This characterization of
scenes allows obtaining the waves parameters, the average one to model its behavior and power to predict its evolution.
In the field of the waves run-up, etc. can be obtained spectra of energy and other parameters for their characterization, the
morphology of submerged bars, identification of return currents. In the port of Barcelona numerous speed data of wind (Vv)
and current were taken (Vc) arriving at a good correlation between both (Vcx (cm/s) = 2,306 Vvx (m/s) + 0,148) and stating that
an influence of other effects are as the tide, reflection of the wharves or diffraction that cannot be avoided.
The images of Radar of synthetic Opening SAR allow to detect episodes of contamination and to analyze the vorticity on great
scale of means. Was surprising the great number of spots identifies. It was verified that the spills follow the Law of Zipp
(hyperbolic distribution between the accidents and their size). Saw that the eddies follow the direction of the submarine tubes.
With the analysis fractal and multifractal of the contour of the spot it is possible to be characterized its origin (human or
natural like masses of plankton) and its aging or persistence, etc. It is verified that it is possible that the intermitency of the
turbulence can obtain parameters by means of measures fractals and that the use of moments of superior order aid to
compare measures of diffusion on different scales by means of the Generalized Law of Richardson. Thus it is related the
slope of the phantom, the intermitency and the temporary dependency of the effective diffusion.
The different agents who produce diffusion in the sea undergo complex not-linear interactions. It, is tried yet to contribute to
include/understand better the
Many experimental and field studies have been devoted to the understanding of non-homogeneous turbulent dynamics. Activity in this area intensified when the basic Kolmogorov self-similar theory was extended to two-dimensional
or quasi 2D turbulent flows such as those appearing in the environment, that seem to control mixing [1,2]. The statistical description and the dynamics of these geophysical flows depend strongly on the distribution of long lived organized (coherent) structures. These flows show a complex topology, but may be subdivided in terms of strongly elliptical domains (high vorticity regions), strong hyperbolic domains (deformation cells with high energy condensations) and the background turbulent field of moderate elliptic and hyperbolic characteristics. It is of fundamental importance to investigate the different influence of these topological diverse regions.
There are several techniques suitable for measuring and modelling dispersion from scalar or velocity-field measurements in a turbulent flow. Each of these has peculiar features and sometimes, even different scaling, and a careful choice has to be made depending on the kind of information available and needed. A useful way to investigate diffusion is to make use of the fractal and multifractal information that ocean and atmospheric flows provide. Here we present some fractal based techniques, where the velocity and scalar fields are related to the spectral spatial information that they provide and are used to predict diffusivity and mixing.In addition an Eulerian description can be obtained by interpolation from Lagrangian information, which is much easier to model via Kinematic Simulation or synthetic turbulence type models, because the detail velocity field is eventually sampled in a random statistical way in the whole domain during their time evolution. It is not possible to get reliable Lagrangian information using PIV since the transformation from the Eulerian description to the Lagrangian one implies an integration in time of the velocity field, especially when considering phenomena that show high sensitivity to initial conditions (turbulent flows). We show some examples of oil spill dispersion in the ocean surface and discuss several multifractal and scaling approaches.
This book series is a collection of the main contributions from the first five workshops held by Ercoftac Special Interest Group on Synthetic Turbulence Models
(SIG42), a summary of each workshop can be found in Ercoftac Bulletin, Synthetic turbulence can model diffusion , and was simulated on a one dimensional grid with a random velocity field. Kraichnan continued
with a random flow field in three dimensions, and constructed an isotropically random sum of unsteady Fourier waves with distributed frequencies.
Most of the applications really started with what was to be called Kinematic Simulation (KS). Kinematic simulation are perhaps the best known of the synthetic
turbulence models. They are based on a simplified incompressible velocity field which kinematically simulates the Eulerian velocity field and is generated as
a sum of random incompressible Fourier modes with a given wavenumber-energy
spectrum. More generally by synthetic turbulence models we mean Lagrangian models
for turbulent diffusion which simulate the Lagrangian statistics that would arise from the underlying Eulerian field. Synthetic turbulence has been used as an approach to understand the general mechanisms of turbulent diffusion, but also to make quantitative predictions of relative dispersion and higher order statistical moments. While remaining as simple a model as possible, synthetic turbulence models are
expected to capture the essence rather than the details of the bigger picture, synthetic turbulence models have now moved from simple to more complex flows, some are discussed in contributions herein, KS for stratified and rotating flows and other complex turbulent flow
Angilella, J.R., Nicolleau, F., Redondo, J.-M.: Synthetic Turbulence Model and Particle-Laden Flows, Ecole de Géologie, Nancy, France. ERCOFTAC Bull. 79, 32–35 (2009)
Redondo, J.-M., Nicolleau, F., Cambon, C.: Synthetic Turbulence Models II, SIG 42 and 35
ERCOFTAC Workshop. ERCOFTAC Bull. 77, 5–7 (2008)
Cornell Mixing Zone Expert System-CORMIX software was used to simulate the behavior of effluents discharged by the underwater emissary in Fortaleza (Ceará, Brazil). This software is used to analyze and predict the discharge design in bodies of water. Application of the CORMIX model was determined to simulate the tracer discharge using local environmental parameters and underwater emissary discharge data. Data on wind, current and position in relation to the coast were used in the chosen case to obtain the discharge flow classification from the model since the hydrodynamic dispersion fields are differentiated by the predominance of different physical processes responsible for the dispersion and mixture of effluents. The simulations carried out
considering the characteristics of the underwater emissary, liquid effluents and receiving medium show a very high dilution capacity. The dilution is directly related to coastal current speed ranging between 1:45 and 1:278, respectively the minimum and maximum for the mixture’s initial zone dilution, with diffuser distances between 16 and 55 meters. This gives the system the characteristic of good dilution capacity compared to other installed systems. At the limit of the simulations, 5.000 m from the diffuser, dilutions reached values between
X1:251 and 1:2.688. From the simulations, it is possible to observe that given the difference in density between the effluent (freshwater) and the sea, the plume presents strong positive buoyancy. Thus, if we consider the unfavorable speeds and currents (0,25-direction and 0,04 - speed) we would have a P = 0,25 x 0,04 or P =0,01 (1%) probability of occurrence. However, for the actual situation, this probability is near zero. The results obtained from using the CORMIX model helped in the environmental monitoring of the effluent disposal area.