Jose M. Redondo | Universitat Politecnica de Catalunya (original) (raw)

Books by Jose M. Redondo

This paper describes the use of surface flow image velocimetry (SFIV) to analyse flow velocity fi... more This paper describes the use of surface flow image velocimetry (SFIV) to analyse flow velocity fields near grated inlets. This will help to understand the flow-capture process of grated inlets and improve their design. The technique allows approximation of the surface flow velocity field where other techniques can fail. Especially in cases when the flow near the inlet is supercritical, and with small depths, the introduction of other devices to measure velocity fields can dramatically modify the flow pattern around the gauge and lead to unreliable measurements. SFIV provides a non-intrusive way of estimating flow velocities in the area covered by the images. Full-scale experiments were carried out using a high-resolution camera and commercial codes to characterise the flow patterns approaching grated inlets commonly used in Barcelona, Spain. The results from image processing algorithms were used to differentiate frontal and lateral flows reaching the inlets.

We discuss a taxonomy of different dynamical features in the ocean surface and provide some eddy ... more We discuss a taxonomy of different dynamical features in the ocean surface and provide some eddy and front statistics, as well as describing some events detected by several satellites and even with additional cruise observations and measurements, in the Northwest Mediter-ranean Sea area between 1996 and 2012. 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 and at the same time provide calibrations for the different local configurations of vortices, spirals, Langmuir cells, oil spills and tensioactive slicks that eventually allow the study of the self-similar structure of the turbulence. Depending on the surface wind and wave level, and also on the fetch. the bathimetry, the spiral parameters and the resolution of vortical features change. Previous descriptions did not include the new wind and buoyancy features. SAR images also show the turbulence structure of the coastal area and the Regions of Fresh Water Influence (ROFI). It is noteworthy tt such complex coastal field-dependent behavior is strongly influenced by stratification and rotation of the turbulence spectrum is observed only in the range smaller than the local Rossby deformation radius, RL. The measures of diffusivity from buoy or tracer experiments are used to calibrate the behavior of different tracers and pollutants , both natural and man-made in the NW Mediter-ranean Sea. Thanks to different polarization and intensity levels in ASAR satellite imagery, these 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 and slick parameters, environmental conditions and history of both oil releases and weather conditions. Eddy diffusivity map derived from SAR measurements of the ocean surface, performing a feature spatial correlation of the available images of the region are presented. Both the multi fractal discrimination of the local features and the diffusivity measurements are important to evaluate the state of the environment. The distribution of meso-scale vortices of size, the Rossby deformation scale and other dominant features can be used to distinguish 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. In a similar way bathimetry may be studied with the methodology described here using the coastline and the thalwegs as generators of local vertical vorticity.

Surface Flow Image Velocimetry (SFIV), is a practical extension of Particle Image Velocimetry (PI... more Surface Flow Image Velocimetry (SFIV), is a practical extension of Particle Image Velocimetry (PIV), as one of the major effective techniques in hydraulics providing velocity and vorticity fields in fast flow laboratory experiments or in field conditions. SFIV uses similar algorithms than conventional PIV, and these tools have a great deal in common with specific pattern matching used in synthetic schlieren. This paper presents an application to characterize the hydraulic behavior of a grate inlet in the area of urban drainage in order to reproduce the velocity field near the grates, as this is one of the important factors for the design of improved inlet systems and prevention of urban flooding. With a high speed camera it is possible to capture images of very high resolution and speed, which combined with the techniques SFIV for image processing, we may generate dynamic velocity and vorticity fields as well as local fluxes around the grate inlet, and combined with flow depth data, evaluate local Froude numbers. The average surface velocity measured by the imaging technique is a good approximation, especially for shallow flows, but it is also possible to extrapolate the technique to rivers, canals, or other hydraulic structures.

We present results on several laboratory experiments where a sharp density interface generated by... more We present results on several laboratory experiments where a sharp density interface generated by either salt concentration or heat, advances due to grid stirred turbulence or to buoyancy. The fractal and multi-fractal measures will be used as a function of the position and time of the advance of the mixing fronts as topological indicators of the multi-scale of these complex flows. There are usually several fractal dimensions for the different physical indicators that may be related to different cascade types in a non-local non-equilibrium turbulent flow. The relationships between the spectra in a turbulent equilibrium cascade and the maximum value of the fractal dimension of a certain set of measurements of a fixed value are related and applied to several self similar situations. We discuss the advances in experimental techniques in the study of turbulence. Different types of visualization techniques and measurement techniques used in laboratory experiments are able to extract information about the intermittency and the self-similarity of the turbulence.

The advance of a Rayleigh-Taylor front is described in Linden & Redondo (1991),[1-3] and may be s... more The advance of a Rayleigh-Taylor front is described in Linden & Redondo (1991),[1-3] and may be shown to
follow a quadratic law in time where the width of the growing region of instability depends on the local mixing
efficiency of the different density fluids that accelerate against each other g is the acceleration and A is the Atwood
number defined as the diference of densities divided by their sum.
This results show the independence of the large amplitude structures on the initial conditions the width of
the mixing region depends also on the intermittency of the turbulence. Then dimensional analysis may also depend
on the relevant reduced acceleration driven time and the molecular reactive time akin to Damkholer number and
the fractal structure of the contact zone [2,4].
Detailed experiments and simulations on RT and RM shock induced fronts analized with respect to structure
functions are able to determine which mechanisms are most effective in local mixing which increase the
effective fractal dimension, as well as the effect of higher order geometrical parameters, such as the structure
functions, in non-homogeneous fluids (Mahjoub et al 1998)[5].
The structure of a Mixing blob shows a relatively sharp head with most of the mixing taking place at the
sides due to what seems to be shear instability very similar to the Kelvin-Helmholtz instabilities, but with sideways
accelerations. The formation of the blobs and spikes with their secondary instabilities produces a turbulent
cascade, evident just after about 1 non-dimensional time unit, from a virtual time origin that takes into account the
linear growth phase, as can be seen by the growth of the fractal dimension for different volume fractions.
Two-dimensional cuts of the 3D flow also show that vortex flows have closed or spiral streamlines around
their core. Examples of such flows can be also seen in the laboratory, for example at the interface of atwo-layer
stratified fluid in a tank in which case streamlines are more regular. Mixing in turbulent flows remains less well
understood, and in spite research some basic problems are still virtually unexplored.

Turbulence is one of the most ubiquitous phenomena in all of fluid mechanics. In the ocean, no le... more Turbulence is one of the most ubiquitous phenomena in all of fluid mechanics. In the ocean, no less than in the atmosphere, is its influence widespread. For example, the interplay between the ocean stratification and the diffusive turbulent motions is often crucial in determining the structure of each. Again, the response of the ocean to large-scale wind and thermal disturbances and the development of ocean currents is dependent on the transfer of matter, momentum and energy by irregular smaller scale motions of one kind or another.
Not all of the random motions found in the ocean, however, can be described properly as turbulence. The characteristic properties of turbulent motions are that they possess a random distribution of vorticity in which there is no unique relation between the frequency and wave number of the Fourier modes; that they are diffusive and dissipative. A distinction is drawn between turbulence in a stably stratified fluid on the one hand and random field of internal gravity waves on the other. This differentiation is useful, not only conceptually but also observationally since the mechanisms of energy transfer (in both physical and Fourier space) are essentially different.
When the wind blows across the surface of the water, a tangential surface stress is developed both directly from the interfacial stress, and indirectly by the rate of momentum loss from the surface waves by such processes as wave breaking. Below the surface, a turbulent mixed layer develops. If the underlying region is statically stable or neutral, the interface between turbulent and non-turbulent fluid is very sharp, and remains so as the turbulence erodes the lower fluid by entrainment. The temperature and salinity in the mixed layer are both virtually uniform as a result of turbulent diffusion, and the continued erosion results in an increasing contrast between the properties of the water in the mixed layer and that immediately below. In this way, a thermocline develops. If, on the other hand, there is substantial surface cooling, there may be a region below the mixed layer in which the density decreases with depth and which is statically unstable. Convective motions can develop and, particularly in polar waters, may extend to considerable depths.
Turbulence in the oceans can also be generated in more familiar ways, such as in shear zones produced by the confluence of different water messes, particularly in estuaries. Turbulence does not invariably occur, however; the stratification may be sufficiently great that the Richardson number is large enough everywhere to prevent the onset of dynamical instability.
Turbulent mixing, and especially turbulent mixing in a density stratified fluid, is a difficult problem in geophysical fluid mechanics, as well as in environmental and industrial studies. Of particular interest is the mixing in the neighbourhood of relatively sharp density interfaces in the oceans, lakes, reservoirs, and the atmosphere. In environmental fluid mechanics, an understanding of these mixing processes is essential in determining water quality in water bodies containing a sharp density interface. The presence of such an interface, by suppressing fluid turbulence, limits the downward transfer of pollutants and gases such as CO2 and O2 from the upper mixed layer. This has important consequences in the design of wastewater and thermal reservoirs. In the atmosphere serve air pollution problems may result from the presence of thermal inversions that inhibit the vertical transport of pollutants. Her again, a knowledge of the exchange processes across the inversion layer is important in predicting and controlling air quality in the atmosphere.
The information that can be obtained on mixing in a stratified fluid is essential for the development of computer models of geophysical phenomena, because, if better predictions are to be made, the distributions of potential and kinetic energy have to be correctly assessed for each process under study.

The purpose will be to describe the different methods applied in swimming research to visualize a... more The purpose will be to describe the different methods applied in swimming research to visualize and understand water movements around the propulsive limbs and their application to improving swimming technique. A compilation of flow visualization methods applied in human swimming research is presented.

Vector Calculus and Fluid Visualization topics used in Remote sensing and gravity measures of the... more Vector Calculus and Fluid Visualization topics used in Remote sensing and gravity measures of the Earth and the Environment.

$Research paper thumbnail of Turbulent transport of sediments and its fractal structure$

Ms Thesis of David Hernandez at ETSECCPB - UPC, Bacelona Tech. 2011

The Universitat Politecnica de Catalunya at the Vilanova i la Geltru Campus (EPSViG) organizes th... more The Universitat Politecnica de Catalunya at the Vilanova i la Geltru Campus (EPSViG) organizes the VIII ADVANCES IN TURBULENCE International conference as the main periodic event of the Xarxa Tematica de Dinamica de Fluids i Turbulencia
Geofisica during 24-26 November 2005.

This series of conferences started in 1992 with a small meeting of 50 participants held at UPC Barcelona which grew steadily.
Advances in Turbulence 4, held in Barcelona in October 1998 had 117 participants from 18 countries and was strongly suported by CNRS, Advances in Turbulence 5 was held at the Universitat de Girona in June 1999 with more than 100 participants, Advances in Turbulence 6 was presented within the wider scope EUROMECH European Turbulence Conference with more than 500 Participants at the Vertex Auditorium in Barcelona, and Advances in Turbulence 7 was held during 21-23 November 2003 in Vilanova i la Geltru with 100 participants. The conference site is a human sized coastal village with many attractive lures to the visitor including food, sights and leisure. The Advances in Turbulence 8 conference will take place hosted by the Campus Universitari de la Mediterrania and the UPC at the Moli de Mar building, near the lighthouse beach.

We welcome all participants to discuss and present their latest work on turbulent flows, mixing, chaotic dynamics and complex systems. The Proceedings Special Issue will be published in English (although presentations and abstracts may be given both in English and French). The full paper if accepted and presented at the conference will be reviewed in either Word or Tex Kluwer templates. All handling of the papers will be electronic and published likely as an special issue after the
conference with the participant list.

XARXA DFTG (Fluid Dynamics and Geophysical Turbulence ) as well as ERCOFTAC SIGS Representing members of the XARXA TEMATICA DE DINAMICA DE FLUIDS I TURBULENCIA GEOFISICA groups are invited to present their main advances in turbulence since the last meeting in 2003. Invited speakers at the conference are . C. Yague (Univ. Complutense Madrid), J. M. Redondo (UPC, Barcelona ) A. Platonov (Hidromet. Institute. St. Petersburg / UPC), J. L. Pelegri / A Viudez (CSIC, ICM Barcelona), B. Fleck (Univ. Alberta, Canada). P. Arnau (Univ. Barcelona) .

An Acrylic Painting exhibition, together with the poster session on Shapes and Patterns in the Environment and a young scientist session related to the European Science week will complement the meeting. See www.campusmed.net for updated information. We also thank CUM and Gencat support.

The Campus Universitari de la Mediterrania, at the Vilanova i la Geltru Campus has hosted several... more The Campus Universitari de la Mediterrania, at the Vilanova i la Geltru Campus has hosted several ERCOFTAC international summer-course on stratified and rotating flows, on turbulent diffusion, on ocean and non-homogeneous Turbulence since 2002. Also similar events have been organized, not only in Vilanova but also in Toulon and Prague since 1999. After ten years of activity, the main motivation, thinking about future summer-courses and workshops has been to gather a selection of the papers and research presentations at the CUM in this volume on Advances in Environmental Turbulence, and to foster new ideas on complex turbulent flows, on the predictive computational ability of diffusion of pollutants in environmental flows improving the understanding of environmental fluid dynamics, their vortical 2D and 3D flows and the small scale turbulence and mixing. Connections with related topics such as wave flows, plankton distribution, oil slick studies, fronts and coastal areas, atmospheric turbulence, non-linear and breaking wave induced flows, stably stratified and rotating turbulent flows and laboratory results are also included in the volume. The editors hope that this issue will help research students in turbulence as well as more advanced researchers.

This book contains a collection of the main contributions from the first five workshops held by E... more This book contains a collection of the main contributions from the first five workshops held by Ercoftac Special Interest Group on Synthetic Turbulence Models (SIG42. It is intended as an illustration of the sig’s activities and of the latest developments in the field.

This volume investigates the use of Kinematic Simulation (KS) and other synthetic turbulence models for the particular application to environmental flows.
This volume offers the best syntheses on the research status in KS, which is widely used in various domains, including Lagrangian aspects in turbulence mixing/stirring, particle dispersion/clustering, and last but not least, aeroacoustics. Flow realizations with complete spatial, and sometime spatio-temporal, dependency, are generated via superposition of random modes (mostly spatial, and sometime spatial and temporal, Fourier modes), with prescribed constraints such as: strict incompressibility (divergence-free velocity field at each point), high Reynolds energy spectrum. Recent improvements consisted in incorporating linear dynamics, for instance in rotating and/or stably-stratified flows, with possible easy generalization to MHD flows, and perhaps to plasmas. KS for channel flows have also been validated. However, the absence of "sweeping effects" in present conventional KS versions is identified as a major drawback in very different applications: inertial particle clustering as well as in aeroacoustics. Nevertheless, this issue was addressed in some reference papers, and merits to be revisited in the light of new studies in progress.

Content Level » Research

Keywords » atmospheric flows - fractal fluids - isotropic turbulence - lagrangian dispersion - multiphase flows - super fluids - synthetic turbulence models

In the present book we collect som of the papers and related works presented in the Workshopd... more In the present book we collect som of the papers and related works presented in the Workshopds organized by the Spanish Pilot Centre of ERCOFTAC (European Research Community on Flow Turbulence and Combustion) in Spain. The meetings were designed to promote contacts between different univerity research groups and industrial partners working in turbulence. The first of these Worshops took place at the facilitiesof the CIMNE, in the Technical University of Catalonia, in Barcelona in February 2003. The second was held in the School of Aeronautic Engineering of the Poly-technical University of Madrid(UPM), in February 2004. Both meetings were devoted to the field of Turbulent flow, in any of its many applications (Industrial, Aeronautical, Environmental, Geo-Astrophysical, etc) or methodologies including; numerical, experimental and theoretical aspects. The main objective was to picture the state of the research in this field in Spain and to create a meeting point for the Spanish and Iberian research groups within the framework of ERCOFTAC. The content of the volume delas with theoretical aspectsof turbulence, with difference methods of numerical simulation (DNS, LES, Kinematic Simulation, RANS), laboratory measurements of turbulence, mixing and complex flows and measurements in the Atmosphere and the Ocean.

In this thesis, after presenting some of the existing knowledge on the different types of force... more In this thesis, after presenting some of the existing knowledge on the different types of forces that swimmers exert on the water in order to propell themselves, the fact that the arm and hand trajectories in the water are very complex and have both sideways and longitudinal components allow to attempt for the first time direct measurements of the lift and drag components of the hand against the water while swimming. Both lift and drag are discussed applying to a hand pushing at an angle against the water the impulse theoreme as well as the Kutta-Joukovskii principle used in aeronautics.

Piezoceramic transductors applied to different positions of swimmer's hands while they swim are used to calculate velocity circulation and lift, as well as pressure differences between the palm and the back of the hand. The unsteady pressure signals are converted also to velocity and are used to identify the changes in hand trajectory and to calculate vorticity.

The lift and drag components of the force are compared against the total force ( with a mean of 13 Kiloponds) with averages of 30% Lift and 70% Drag for competitive swimmers.

Different configurations of oscillating grid generated turbulence are used in order to lift a lay... more Different configurations of oscillating grid generated turbulence are used in order to lift a layer of sediment. The sediment- turbulence interactions are studied. The level of vorticity at the sediment lutocline is important to predict the height of the lutocline (sharp density interface produced by the lift off sediment layer). The Shields parameters are measured for a wide range of sediment size distribution. Shear lift off processes are compared with zero-mean flow and the level of turbulence needed for lift-off is measured with ADV and advanced video techniques.

These pages are collected summaries of communications presented at the Fourth Workshop on Resear... more These pages are collected summaries of communications presented at the Fourth
Workshop on Research in Turbulence and Transition, held at Instituto Superior
T´ecnico, in Lisbon on October 16th, 2009. The first edition of this Workshop was
held on February 6, 2003 at the International Centre for Numerical Methods in Engineering
at the Technical University of Catalonia, the second was held at the School
of Aeronautical Engineering at the Technical University Madrid on February 12 of
2004, and the third one took place in the College of Engineering at the University
of Seville on October 17, 2008.
These Workshops have been conducted at the initiative of CIMNE, Iberian-East and
Iberian-West Pilot Centres of the European Research Community on Flow, Turbulence
and Combustion (ERCOFTAC), and is a Europe-wide organization that promotes
research on topics related to fluid dynamics, turbulence and combustion, and
their industrial applications. More information can be found at www.ercoftac.org
The aim of this Workshop is to contribute to a better knowledge of the activities
carried out by various Iberian research groups in any field relevant to the turbulence
or/and Transition. The papers presented correspond to groups from Madrid,
Barcelona, Seville, Zaragoza, Tarragona, Girona, Lisbon, OPorto, Coimbra, and
Beira Interior.
The organizers of the Workshop want to thank the IDMEC at Instituto Superior
T´ecnico, Technical University of Lisbon.

Analysis of turbulence and its governing laws is the source of a large researching effort into wh... more Analysis of turbulence and its governing laws is the source of a large researching effort into which experimental campaigns play a main role. The most used experiments to describe the
phenomenon are based on tracers tracking which are set in a tank of fluid where a turbulence is created by means of a grid.

One of the fields of larger complexity is the study of turbulence
phenomena within a state of stratificacion which is defined by a
halocline. In this work a set of experiments have been performed
from a classical experimental device in which some variations
have been introduced in order to gather a larger amount of
information at a lower cost. A first objective is the validation of this new device by studying basic laws in no stritified conditions. A second objective is the performing of a detailed study on the
influence of stratification on energy and vorticity decaying laws,
conduct an in-depht study of kinetic energy transference laws and the analysis of the vortex number evolution at a different
enstrophy levels. For these purposes a wide range of computer
tools have been used, including image capturing and processing,
fluid mechanics specific programs and stadistic software

$Research paper thumbnail of Turbulent transport of sediments and its fractal structure$

Ms Thesis of David Hernandez at ETSECCPB - UPC, Bacelona Tech. 2011

Content Level » Research

Keywords » atmospheric flows - fractal fluids - isotropic turbulence - lagrangian dispersion - multiphase flows - super fluids - synthetic turbulence models

The lift and drag components of the force are compared against the total force ( with a mean of 13 Kiloponds) with averages of 30% Lift and 70% Drag for competitive swimmers.

$Research paper thumbnail of Multifractal observations of eddies, oil spills and natural slicks in the ocean surface$

Il Nuovo Cimento C, 2008

Natural and man-made distributions of tensioactive substance concentrations in the sea surface fe... more Natural and man-made distributions of tensioactive substance concentrations in the sea surface features exhibit self-similarity at all radar reflectivity levels when illuminated by SAR. This allows the investigation of the traces produced by vortices and other features in the ocean surface. The man-made oil spills besides often presenting some linear axis of the pollutant concentration produced by moving ships also show their artificial production in the sea surface by the reduced range of scales, which widens as time measured in terms of the local eddy diffusivity distorts the shape of the oil spills. Thanks to this, multifractal analysis of the different backscattered intensity levels in SAR imagery can be used to distinguish between natural and man-made sea surface features due to their distinct self-similar properties. The differences are detected using the multifractal box-counting algorithm on different sets of SAR images giving also information on the age of the spills. Different multifractal algorithms are compared presenting the differences in scaling as a function of some physical generating process such as the locality or the spectral energy cascade.

Estuarine, Coastal and Shelf Science, 2008

Spatial and temporal variations in the distribution of the marine picoplanktic cyanobacteria popu... more Spatial and temporal variations in the distribution of the marine picoplanktic cyanobacteria population and mixing conditions were found in the Ebro River estuary outflow to the Mediterranean Sea in Spain. Six sampling surveys were undertaken between July 1999 and February 2000 for distances up to 15 km from the river mouth. Measurements were taken of flow velocity, salinity, temperature, depth and picocyanobacteria (PCB) abundances. Gradient Richardson (Rig) and Reynolds (Re) numbers were determined to evaluate hydrodynamics. In summer, large values of Rig arise from the small flow rates, and small values of velocity shear between the surface fresh water layer and the bottom saline layer; conversely, in winter the large flow rates and attendant large velocity shears between the layers give rise to small values of Rig. Flow conditions in the fall are an intermediate case between the summer and winter cases. Vertical abundance distributions were resolved through the river water, interfacial region, and the bottom salt wedge; longitudinal gradients of PCB abundances were also resolved. Seasonal differences in the PCB abundance values were observed. Analysis of cell numbers (C ) showed that the variable dC/dS, the dependence of cell number upon salinity gradient (dS ) was critical. A non-dimensional number; the cellular gradient number (Cg) is introduced. Cg has useful biological interpretations that can potentially be included in ecological modeling. For example, Cg ¼ 1 pertains to perfect adaptability of the organism to adjust to changing environmental conditions, whereas Cg ¼ 0 describes total mortality. For a system with strong advection there is insufficient time for cells to adapt to the changing environment, and so those cell counts are unchanged. This is the case for the Ebro estuary in winter as advection of salinity (and hence PCB abundance) dominates the other loss processes for large flow rates.

In this work a study both the internal turbulence energy cascade intermittency evaluated from win... more In this work a study both the internal turbulence energy cascade intermittency evaluated from wind speed series in the atmospheric boundary layer, as well as the role of external or forcing intermittency based on the flatness (Vindel et al 2008)is carried out. The degree of intermittency in the stratified ABL flow (Cuxart et al. 2000) can be studied as the deviation, from the linear form, of the absolute scaling exponents of the structure functions as well as generalizing for non-isotropic and non-homogeneous turbulence, even in non-inertial ranges (in the Kolmogorov-Kraichnan sense) where the scaling exponents are not constant. The degree of intermittency, evaluated in the non-local quasi-inertial range, is explained from the variation with scale of the energy transfer as well as the dissipation. The scale to scale transfer and the structure function scaling exponents are calculated and from these the intermittency parametres. The turbulent diffusivity could also be estimated and compared with Richardson's law. Some two point correlations and time lag calculations are used to investigate the time and spatial integral length scales obtained from both Lagrangian and Eulerian correlations and functions, and we compare these results with both theoretical and laboratory data. We develop a theoretical description of how to measure the different levels of intermittency following (Mahjoub et al. 1998, 2000) and the role of locality in higher order exponents of structure function analysis. Vindel J.M., Yague C. and Redondo J.M. (2008) Structure function analysis and intermittency in the ABL. Nonlin. Processes Geophys., 15, 915-929. Cuxart J, Yague C, Morales G, Terradellas E, Orbe J, Calvo J, Fernández A, Soler M R, Infante C, Buenestado P, Espinalt A, Joergensen H E, Rees J M, Vilá J, Redondo J M, Cantalapiedra R and Conangla L (2000): Stable atmospheric boundary-layer experiment in Spain (Sables 98): a report, Boundary-Layer Meteorology 96, 337-370 Mahjoub O.B., Babiano A. and Redondo J.M. (1998) Structure functions in complex flows. Journal of Flow Turbulence and Combustion. 59, 299-313. Mahjoub O.B., Redondo J.M. and Babiano A. (2000) Self similarity and intermittency in a turbulent non-homogeneous wake. Proceedings of the Eighth European Turbulence Conference. (Eds. Dopazo et al.) CIMNE, Barcelona, 783-786. Mahjoub O.B., Redondo J.M., and R. Alami, (1998) Turbulent Structure Functions in Geophysical Flows, Rapp. Comm. int. Mer Medit., 35, 126-127.

Dynamics of Atmospheres and Oceans, 1996

Probability distribution of basic instabilities appearing in stratified flows and point density f... more Probability distribution of basic instabilities appearing in stratified flows and point density fluctuations have been studied. Various parameters of the mixing process have been changed in the experiments, to investigate mixing. Detailed flow visualization as well as density measurements have been used in zero-mean-flow laboratory experiments involving grid-stirred turbulent mixing across a density interface and bubble-induced mixing. The overall mixing efficiency of the processes depends on the local Richardson number as well as on the local vorticity. Parameter distributions of low and high mixedness corresponding to different instabilities are presented, showing that dipolar vortices penetrating the interface are the most efficient mixing instabilities.

A series of experiments on turbidity currents are presented, using the turbulent energy equation ... more A series of experiments on turbidity currents are presented, using the turbulent energy equation balance with the buoyancy term modelled in terms of the settling velocity. The highly concentrated mud turbidities exhibit non-newtonian effects which may be related to the entrainment experiments of Wolansky and Brush [Tellus 1975]. The influence of slope is also studied in weak and strong entrainment sliding flows.

In many geophysical phenomena with great environmental interest appear simple processes that gene... more In many geophysical phenomena with great environmental interest appear simple processes that generate complexity (Mandelbrot 1967). This can be found so much as in the growth of an ice crystal, the ramifications of a river basin or in the flow of a river or the ocean as long as the Reynolds number is high and the regime corresponds to a turbulent fluid flow.

Abstract Some results on pollutant dispersion modelling and tracer measurements for the Mediterra... more Abstract
Some results on pollutant dispersion modelling and tracer measurements for the Mediterranean Spanish coast are presented. Two hydrodynamic models have been used to simulate wind and wave induced circulation in the nearshore and surf zones respectively. A “near field” model has been used in order to simulate the initial conditions for the local “far field” dispersion model. Two study cases are presented: The first one shows the mixing of conservative tracers in a Mediterranean surf zone from an experimental and numerical models used to predict bacterial dispersion from the main sea outfalls of Barcelona City. The comparison between dye dispersion experiments and model in the surf zone is good, while the outfall predictions show the importance of accurately modelling the effects of buoyancy on the plume.

This book series is a collection of the main contributions from the first five workshops held by ... more 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.
It is intended as an illustration of the sig’s activities and of the latest developments in the field.
Synthetic turbulence can be traced back to the 80's, in which diffusion was simulated
on a one dimensional grid with a random velocity field. Kraichnan continued with a random flow field in three dimensions, and constructed incompressible fields
as 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.

The aim of this study was to compare the running-drip method (RDi) (Baraka 1972), a simple techni... more The aim of this study was to compare the running-drip method (RDi) (Baraka 1972), a simple technique never used in animals, with the hanging drop (HDo) technique in dogs in sternal (S) and lateral (L) recumbency.

Harvard Deusto Marketing Y Ventas, 2006

Título: Retos de la convergencia tecnológica Autores: Redondo, José Manuel Revista: Harvard-Deust... more Título: Retos de la convergencia tecnológica Autores: Redondo, José Manuel Revista: Harvard-Deusto Marketing & Ventas, 2006 MAY-JUN; (74) Página(s): 66-69 ISSN: 11337672 Resumen: Las nuevas tecnologías abren un mundo de posibilidades a las marcas para ...

Física de la …, 2009

Se presenta un sencillo modelo de laboratorio para generar mezcla turbulenta entre dos fluidos mi... more Se presenta un sencillo modelo de laboratorio para generar mezcla turbulenta entre dos fluidos miscibles que están en una situación inicial inestable en un campo gravitatorio. El proceso de mezcla se genera por medio de la evolución de un conjunto discreto de penachos ...

Turbulent transfer is one of the most important processes in the Atmospheric Boundary Layer (ABL)... more 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.
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 [1].
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?

Turbulence affects the dynamics and the evolution of the turbulent mixing layer and its complex c... more 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.

In colloquial speech the term "turbulence" means any flow with complicated temporal and spatial d... more In colloquial speech the term "turbulence" means any flow with complicated temporal and spatial dynamics. In contrast, the properties of these flows are supposed to be described by models which are based on the assumption of a precise and very well defined setting. This paper is an attempt to review the fundamentals of turbulence theory, with emphasis on non-fully developed turbulence.

Scientometrics

This review focuses on the effects of small-scale turbulence on the rate processes of copepods, a... more This review focuses on the effects of small-scale turbulence on the rate processes of copepods, an important group of planktonic animals, and on their consequences for the dynamics of pelagic ecosystems. Turbulent water motion enhances the encounter rates between planktonic organisms and their food, changing the perception of the food environment for copepods and other planktonic animals. As a consequence, their feeding behaviour is affected, and the grazing rates significantly increased. Direct effects of small-scale turbulence for planktonic copepods also include the enhancement of metabolic energy expenditure, excretion rates, growth, and development rates. Through complex cumulative processes of the changes on individual rate-processes, the structural and functional properties of planktonic ecosystems are modified, with important consequences for the ultimate fate of biogenic carbon in aquatic systems.

for the 9th International Workshop on the Physics of Compressible Turbulent Mixing July 2004 Camb... more for the 9th International Workshop on the Physics of Compressible Turbulent Mixing July 2004 Cambridge, UK Edited by S.B. Dalziel

Molecular mixing in the early stages of RT has been directly visualised with LIF in a similar set... more Molecular mixing in the early stages of RT has been directly visualised with LIF in a similar set up as in Linden nd Redondo(1991), Here reactive mixing using chemical tracers has been used to define the Laser Induced Fluoresceine mixing.
Arguments based on growth rate used to justify accuracy of Front-Tracking schemes are shown to be inaccurate
MILES simulations appear to provide a reasonable approximation to the mixing behaviour

There are several techniques suitable for measuring and modelling dispersion from scalar or veloc... more 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

Call for the ERCOFTAC-CNRS-UPC-CIMNE-CUM Summercourse and workshop (near Barcelona) from 30 Jun... more Call for the ERCOFTAC-CNRS-UPC-CIMNE-CUM Summercourse and workshop (near Barcelona) from 30 June-5 July

organized by

The list of abstracts and papers presented at the Summer-school and workshop of the ERCOFTAC, Ins... more The list of abstracts and papers presented at the Summer-school and workshop of the ERCOFTAC, Inst. of Mathematics CAS, Pittsburg Univ. USA and Czech Technical Univertity, is presented for future meetings of the Pan European Laboratory on Non Homogeneous Turbulence (ERCOFTAC).
A list of contributions compiled by Tomas Bodnar et al. may be found at: http://www.prague-sum.com/site/page/view/download.

Here only Workshop presentations are resumed;

Dagmar Medková / Robin problem for the Oseen system
Milan Pokorný / A Linearized Model for Compressible Flow past a Rotating Obstacle: Analysis via Modified Bochner–Riesz Multipliers
Philippe Fraunie / Two phase flow modeling
Adélia Sequeira / An Overview of Some Mathematical Models for Blood Coagulation
David Wegmann / An Improved Energy Inequality for Weak Solutions of the Navier-Stokes Equations
Jonas Sauer / Maximal Lp-Regularity of the Spatially Periodic Stokes Operator
Petr Sváček / On the conservation of the energy for incompressible flow interacting with solid bodies/particles
Hana Mizerová / Existence, uniqueness and approximation of the diffusive Peterlin viscoelastic model
Peter Otčenáš / A numerical approximation of an equation of the wall in the fluid-structure interaction problem
Evgeniya Stepanova / Flow Pattern Comparison of Miscible and Solid Markers in Compound Vortex
Vladimír Hric / Numerical Solution of Transonic Wet Steam Flow with Non-equilibrium Condensation
Viktor Šíp / Development of FVM Solver for ABL Flows
Nikolay Shevtsov / Visualization of waves on the free surface of the compound vortex
Tobias Seitz / Flow Reconstruction from MRV Measurements
Xiaoxin Zheng / Time-dependent singularities in the Navier-Stokes system
Benyahia Mohamed / On the weak solutions to the Fluid/Rigid Body interaction problem
Johannes Brand / Fluid Flows & Floating Bodies
Joana Silva / The Impact of the Sea-level Rise in the Hydromorphology of Alluvial Rivers
Giusy Mazzone / On the inertial motions of liquid-filled rigid body with slip boundary conditions
Tomoyuki Nakatsuka / On uniqueness of symmetric Navier-Stokes flows around a body in the plane
Václav Mácha / Self-propelled motion in a viscous compressible fluid
David Wegmann / An Improved Energy Inequality for Weak Solutions of the Navier-Stokes Equations
Irina Denisova / On energy inequality for evolution problem for two fluids of different types without surface tension
Eliška Cézová / Exploratory analysis of meteorological data measured in opencast coal mine
Luboš Matějíček / On the experimental and numerical study of dust dispersion in complex terrain
Jiří Neustupa / On steady solutions of the Bénard problem in a two dimensional quadrangular cavity
Ondřej Kreml / On bounded solutions to the compressible isentropic Euler system
Martin Kalousek / Homogenization of a non-Newtonian flow through a porous medium
Jose Manuel Redondo / Lift off and turbidity currents in the environment
Jose Manuel Redondo / PIV of convective complex flows driven by thermoelectric heat fluxes
David Maltese / Error estimates for a numerical approximation to the compressible barotropic Navier-Stokes equations

Topics used during our Environmental Turbulence Lectures during Fall 2015 at UPC, Barcelona Tech... more Topics used during our Environmental Turbulence Lectures during Fall 2015 at UPC, Barcelona Tech. It adresses Lagrangian and Hailtonian Basic concepts

The satellite-borne SAR and ASAR seems to be an excellent system not only to detect man-made oil ... more The satellite-borne SAR and ASAR seems to be an excellent system
not only to detect man-made oil spills and tensioactive slicks but it
also detects dynamic features and the ocean eddies of different sizes.
The study of the topology of the regions of different rugosity of the
ocean can map the vortical, eliptical regions as well as the hyperbolic
shear dominated areas, is also a convenient tool to investigate the
eddy structures, the scale to scale energy and enstrophy transfer of a
certain area, and to calculate the eddy diffusivity values.
The effect of bathymetry and local currents are important in describing
the ocean surface behavior. In the NW Mediterranean the maximum
eddy size agrees remarkably well with the limit imposed by the local
Rossby deformation radius using the usual thermocline induced
stratification, Redondo and Platonov (2001).

The workshop is focussed on the subject of Environmental Turbulence and its relation with geophys... more The workshop is focussed on the subject of Environmental Turbulence and its relation with geophysical, biological and astrophysical applications. The main motivation for this workshop is to create a multidisciplinary environment and to discuss and study non-linear aspects of turbulence and their effects on non-homogeneous, non-isotropic and non-stationary media which are fundamental in real flows.

Due to high cost of satellite images, and the wealth of new physical local information obtained f... more Due to high cost of satellite images, and the wealth of new physical local information obtained from the sea surface, it is worthwhile to implement new types of image analysis that can relate dynamical turbulence information to measurable multi-scale descriptors. SAR and ASAR (Advanced Synthetic Aperture Radar) are well designed to determine locally the roughness of the sea surface, and we use this property to investigate the structure of river plumes and of coastal flows, the polarimetric information from the SAR can also be used to investigate the lower atmosphere. The topological characteristics of the shape of the river plumes marked by the rugosity of the river brakish water floating over the salty Mediterranean water, when analzsed in detail reveals a very complex nature. Several features, such as the local Reynolds number, the Richardson number and the distance from the wall, all affect the multi-fractal spectra as well as the maximum Fractal Dimension or Kolmogorov capacity Lane Serf (1993). The asymmetry between the coastal side and the deep ocean side of the river plumes, may be used to improve the estimates of local eddy diffusivity from satellite images. The relationships presented relating the structure functions and the multifractal indicators, agree with a 2D generalized Richardson's dispersion Law (Castilla et al. 2007). -F. Nirchio, S. Di Tomaso W. Biamino, E. Parisato, P. Trivero, A. Giancasp (2005) -Oil spills automatic detection from sar images

Una barra metálica de longitud se mueve en el interior de un campo magnético uniforme ( ) con vel... more Una barra metálica de longitud se mueve en el interior de un campo magnético uniforme ( ) con velocidad constante , siendo perpendicular tanto al eje de la varilla como al campo magnético y de módulo .

Resumen: La aparición de múltiples escalas, que interactúan entre si en diversos fenómenos físico... more Resumen: La aparición de múltiples escalas, que interactúan entre si en diversos fenómenos físicos medioambientales, especialmente cuando el régimen fluido es turbulento, exige métodos de análisis nuevos. El análisis multi-fractal permite cuantificar el nivel de complejidad geométrico y en algunos casos a partir de una caracterización geométrica se pueden predecir algunos aspectos dinámicos del fluido. Se aplica el método de Box-Counting (conteo de cajas) para calcular la dimensión fractal o capacidad de Kolmogorov a observaciones de nubes obtenidas mediante las imágenes de satélite de la Atmósfera (Infrarrojo IR y Visible) y de superficie del Océano (Radar de Apertura Sintética SAR). En todos los casos las diferencias en complejidad entre los distintos tonos de gris detectados en las imágenes de satélites de estructuras atmosféricas, derrames de crudo o penachos de aguas contaminadas en la superficie marina son un reflejo de las condiciones físicas ambientales del medio fluido atmosférico u oceánico y nos permiten entender mejor los procesos dinámicos y de transporte de energía a distintas escalas del flujo analizado.

The statistical analysis of larger data sets (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(200... more The statistical analysis of larger data sets (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005) from the collection of the SAR images, including new images obtained from ESA (ENVISAT and ERS-2) as well as further SAR/ASAR images obtained directly from ESA(C1P.2240) (2000-2007)has been used both to analyse the Sea Surface features, such as slicks and vortices as well as oil spills. Images during a 9 yr period have been analysed, using at the same time a more comprehensive identification of the topology associated to patterns and eddies detected in the ocean surface. More than 2000 synthetic aperture radar (SAR and ASAR) as well as other types of images have been compared over the test site used by the Clean Seas proyect in the NW Mediterranean sea. We have analyzed these SAR images with respect to radar signatures of (natural and man-made) oil pollution and other surface features. The extension of most of the SAR detected vortices (63 %) is less than 100 Km2. 33% of vortices occupy an area between 100 to 500 Km2 and only 4% of the vortices possess a large area between 500 and 1200 Km2. About a 93% of vortices have a diameter less than 20 Km. Most detected vortices (79%)have elipticities between 1.125 -1.625. The vortices in the NW Mediterranean exhibit a binormal distribution of the vortices and we consider that there exist two main types of mechanisms related to their orientation: Dynamical, mostly due to the influence of the Liguro-Provenzal current (about 50% of the detected vortices have direction angles between 250 and 750 and bathymetrical, due to the influence of the submarine canyons situated mostly perpendicularly to the coast line (25% of the cases the detected vortices have azimuth angles between 125 and 145 degrees near Barcelona.

Design and operation of thermoelectric coolers and heaters as well as the fluid mechanics of conv... more Design and operation of thermoelectric coolers and heaters as well as the fluid mechanics of convection is important [1]. We present a university-industrial colaboration that developed transient Thermoelectric driven convective models based on the control of thermal boundary conditions and flow measurements inside a closed enclosure for didactic uses. The coupling of heat transfer and electric conduction within semiconductors is important and takes into account all thermoelectric effects, including Joule and Seebeck heating, Thomson effect, Peltier effect and Fourier's heat conduction. We present a Thermoelectric driven heating and cooling experimental device in order to map the different transitions between two dimensional convection in an enclosure and the 3 D complex flows. The size of the box 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 [2,3]. The buoyancy driven flows are generated by Seebeck and Peltier effects in 4 to 40 wall positions. The parameter range of convective cell array varies strongly with the topology of the boundary conditions and buoyancy [4]. At present side and vertical 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 any angle [5,6] (Redondo 1995, Redondo et al.2013). Fluid visualizations are performed by PIV, Particle tracking and shadowgraph/schliering [4]. Thermoelectric coolers offer the potential to better control and enhance the cooling of electronic modules to regulate operating temperatures or to allow higher power. Thermoelectric coolers are limited by the maximum heat fluxes and have lower coefficient of performance (COP) but offer a wide range of boundary fluid control. Environmental and Engineering Fluid Mechanics laboratories at university or professional schools may incorporate student practical work in several of many fields that need understanding such as:

Design and operation of thermoelectric coolers and heaters that may be used in detailled laborato... more Design and operation of thermoelectric coolers and heaters that may be used in detailled laboratory experiments of buoyancy driven trurbulence, as well as in the general fluid mechanics of convection is important, there seems to be a lack of comparison between numerical models of turbulent flows (Including Kinematic Simulation and DNS) and non-homogeneous experiments. [1-3] We present the results of a university-industrial colaboration that developed a Fluid Dynamic Didactic Apparatus able to model steady and transient Thermoelectric driven convective models based on the control of thermal boundary conditions and also optimized to perform flow measurements inside a closed enclosure. The Thermoelectric Convection Didactic Device (TCDD) presented here is basically designed for a range of didactic uses, but a wide range of innovative research options are available, both in the small 4x4 device shown in figure 1 and in larger and higher power equipments. We present here both the thermoelectric and the fluid flow description of the TCDD. The coupling of heat transfer and electric conduction within the semiconductor Thermal assemblies is important and takes into account the local thermoelectric effects, including Joule and Seebeck heating, Thomson effect, Peltier effect and Fouriers heat conduction. The macroscale heating cooling equations are presented together with the calibration and flow characteristics of the thermolectric convective devices shown only for an example configuration, but many other are possible.

Information about the workshop on Bio-Environmental TURBULENCE to be held by CUM in Barcelona, C... more Information about the workshop on Bio-Environmental TURBULENCE to be held by CUM in Barcelona, Castelldefels, Vilanova i la Geltru and Tarragona during 22-29 June 2017