217 research outputs found
Ecological design of a crayfishing program to control population density of the invasive species Procambarus Clarkii in Doñana National Park freshwater marsh (Spain)
The exploitation of Procambarus clarkii in Doñana National Park’s freshwater marsh (DNP) has been economically important to the local human population since the 1970s. The high density of this crayfish species has been causing a major environmental impact in the Park by the substantial reduction of submerging aquatic macrophytes prairies due to its broad trophic spectrum and feeding habits, which turned the environmental frame (consisting in clear water equilibrium) into a turbid water balance. Differences in population dynamics of three population groups of P. clarkii in the DNP freshwater marsh were compared and analyzed from a fishery perspective. The objective is to reduce their ecological impact using optimal crayfishing management. Maximum growth curves showed that crayfish have different growth optimums. Recruitment of young crayfish varies between different populations; when there is an excessive increase in the density of juveniles in a population and conditions are stressful, their growth is deficient. If these conditions persist, the population could become stunted. Fishery for commercial gain is banned in DNP; however, a model of fisheries program aimed at controlling the excess population of crayfish can be effective in halting the ecological impact of this invasive species while providing an opportunity for poachers to have viable productive options. The model proposed can help to solve the problem of crayfish “poaching” through the legalization and strict control of harvesting practicesPedro J. Gutiérrez-Yurrita also thanks the ICI (Spain) for a subvention grant and CONACyT (México) for a financial complement of the former grant that enabled him to complete this researc
Analysis of the Patent of a Protective Cover for Vertical-Axis Wind Turbines (VAWTs): Simulations of Wind Flow
This paper presents a numerical and experimental analysis of the patent of a
device to be used in vertical-axis wind turbines (VAWTs) under extreme wind
conditions. The device consists of two hemispheres interconnected by a set of
conveniently implemented variable section ducts through which the wind
circulates to the blades. Furthermore, the design of the cross-section of the
ducts allows the control of the wind speed inside the device. These ducts are
intended to work as diffusers or nozzles, depending on the needs of the
installation site. Simulations were performed for the case of high-speed
external wind, for which the ducts act as diffusers to reduce wind speed and
maintain a well-functioning internal turbine. Four different patent designs
were analyzed, focusing on turbine performance and generated power. The results
indicate that the patent allows the generation of electric power for a greater
range of wind speeds than with a normal wind turbine. The results support that
this patent may be a good alternative for wind power generation in geographic
areas with extreme weather conditions or with maintained or strong gusty wind.
Experimental tests were carried out on the movement of the blades using the
available model. Finally, the power curve of the model of this wind turbine was
obtained.Comment: 22 pages, 15 figure
Smoke and fire dynamics in atria and large enclosures: An overview
The proliferation of atria within modern large buildings is relatively recent. An atrium can be defined as a large open space connecting two or more storeys. Atria are important architectonical features since the 60's and can be found, among others, in shopping centres, office buildings and high-rise buildings, airports, stations and sports centres. However, the atrium represents an innovative, complex and non conventional architectonical element that can lead to fire environments diverging significantly from those in conventional compartments used in the development of current codes and standards. They are a source of discussion in the fire safety community because smoke can easily spread from one floor to another making the traditional methodologies for compartmentation of little or null effect. The design of smoke management in atria has been based on prescriptive codes since the 70's. It was not until the mid 80's that the phenomena started to be the objective of both experimental and numerical studies. It is because of the subsequent improved understanding on fire dynamics and smoke management together with the increased computing power available nowadays, that there is a progressive movement from prescriptive-based to performance-based codes which is also chaning the way atria are designed. The aim of the present work is to provide a broad overview of the current state-of-the-art of fires in atria. A brief introduction to the characteristics and types of atrium structures is presented first. Then, a description of the fire dynamics as well as the main safety problems that arise in case of fire are considered. A historical discussion of the research, including experimental and numerical studies, is presented, and current design methodologies and fire safety strategies are discussed. The final part of the overview addresses the international tendencies towards the introduction of performance-based fire protection codes. This overview highlights the need for further experimental studies and validations of numerical simulations for a wider range of fire conditions. © 2010 by Nova Science Publishers, Inc. All rights reserved
Could be possible to innovate in Veterinary TFG?
Resúmenes IV Congreso VetDoc de Docencia Veterinaria, León 2017 (6-7 de Julio)[ES] Se ha realizado un análisis comparativo sobre las características de los TFG en todos los grados en Veterinaria de las Universidades Públicas Españolas. En la Facultad de Veterinaria de Murcia, el TFG consiste en la realización de un trabajo de investigación de unos 30 folios con estructura similar a un trabajo de investigación científica además de la presentación de dicho trabajo en exposición y defensa pública ante un tribunal
Controlled formation of bubbles in a planar co-flow configuration
We present a new method that allows to control the bubble size and formation frequency in a planar air-water co-flow configuration by modulating the Water velocity at the nozzle exit. The forcing process has been experimentally characterized determining the amplitude of the water velocity fluctuations from measurements of the pressure variations in the water stream. The effect of the forcing on the bubbling process has been described by analyzing the pressute signals in the air stream in combinatiOn with visualizations performed with a high-speed camera. We show that, when the forcing amplitude is sufficiently large, the bubbles can be generated at a rate different from the natural bubbling frequency, f(n), which depends on the water-to-air velocity ratio, Lambda u(n)/u(q), and the Weber number, We rho(w)u(n)(2)H(0)/sigma, where 110 is the half-thickness of the air stream at the exit slit, rho(w), the water density and a the surface tension coefficient. Consequently, when the forcing is effective, monodisperse bubbles, of sizes smaller than those generated without stimulation, are produced at the prescribed frequency, f(f) > f(n). The effect of the forcing process on the bubble size is also characterized by measuring the resulting intact length, 1, i.e. the length of the air stem that remains attached to the injector when a bubble is released. In addition, the physics behind the forcing procedure is explained as a purely kinematic mechanism that is added to the effect of the pressure evolution inside the air stream that would take place in the unforced case. Finally, the downstream position of the maximum perturbation amplitude has been determined by a one-dimensional model, exhibiting a good agreement with both experiments and numerical simulations performed with OpenFOAM.This work has been supported by the Spanish MINECO (Subdirección General de Gestión de Ayudas a la Investigación), Junta de Andalucía and European Funds, grants Nos. DPI2014-59292-C3-1-P, DPI2014-59292-C3-3-P, P11-TEP7495. Financial support from the University of Jaén, Project No. UJA2013/08/05, is also acknowledged
Floquet stability analysis of a two-layer oscillatory flow near a flexible wall
We investigate the linear Floquet stability of two fluid layers undergoing oscillations
in the direction parallel to the flexible wall that separates them. This canonical
configuration is inspired by the cerebrospinal fluid flow in the spinal canal of subjects with
hydromyelia/syringomyelia. The analysis focuses on the marginal conditions for the onset
of instability, and how these depend on the spatial wavelength of the perturbation, and
on the values of the control parameters, which are the two channel widths, the Reynolds
number and the wall stiffness. Unstable perturbations are found to oscillate synchronous
with the base flow. The wavelength of the most unstable perturbation, of the order of the
stroke length of the basic oscillatory motion, depends strongly on the wall stiffness, but is
only weakly influenced by the channel widths and the Reynolds number. In general, around
criticality, it was found that increasing the Reynolds number has a destabilizing effect, and
that decreasing the canal widths stabilizes the instability. The wall stiffness on the other
hand has a non-monotonic effect, exhibiting an intermediate value for which the instability
is maximally amplified. The present analysis is a first step towards a better understanding
of the physical mechanisms that govern many (bio)fluid mechanical problems that involve
oscillatory flows near compliant walls.Coordinated project, PID2020-115961RB-C31, PID2020-115961RBC32
and PID2020-115961RA-C33, financed by MCIN/AEI/10.13039/501100011033Junta de
Andalucía and European Funds, project no. P18-FR-4619Funding for open access charge provided by
Universidad de Granad
An experimental and numerical study of the smoke ventilation in atrium fires under dynamic ventilation performance
Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.Smoke control systems within fire safety designs are being commonly investigated by means of computation fluid dynamics (CFD) models due to the increment of accuracy and computational speed. This paper presents a full-scale experimental and numerical comparison of atrium fires of 2.3- 2.7 MW and 5.1-5.3 MW using Fire Dynamic Simulator (FDSv6). Results from six different fire tests with dynamic and constant exhaust flow rates during the fire are presented. Different mesh element sizes as well as turbulence models (Deardorff, Dynamic Smagorinsky and Smagorinsky models) assessing the smoke layer interface are compared presentingdifferences in the steady state of 20% and 10%, respectively. A good agreement is obtained numerically, being the average relative error during the whole experiment of 12% and 17% in low and high heat release rates, respectively. Finally, the smoke layer has been well predicted not only under constant flow rates but also under dynamic flow rates, being the numerical temporal response to the exhaust changes conducted slower than the experimental one.cf201
Drag reduction on a blunt body by self-adaption of rear flexibly hinged flaps
We study the aerodynamics of a blunt-based body with rear flexibly-hinged rigid flaps,
subject to a turbulent flow of Reynolds number Re = 12000, under aligned and cross
flow conditions with yaw angle β = 0◦ and β = 4◦. To that aim, different values of
the equivalent torsional stiffness are considered, to cover the range of reduced velocity
U∗ = (0, 3.48] in water tank experiments. The effect of the angular deflection of
plates on the drag and near wake flow is analyzed, experimentally and numerically.
The results show that, in the range of U∗ herein considered, the plates undergo an
inwards quasi-static, self-adaptive deflection, which is symmetric for yaw angles β = 0◦
and asymmetric for β = 4◦. In particular, the plates feature small mean deformation
angles for values of U∗ < 1, whereas a sharp and monotonic increase of such deflection
occurs for U∗ > 1, i.e. for lower values of the hinge’s stiffness, with an asymptotic
trend towards the larger values of U∗. A critical value of reduced velocity of U∗ ≃ 0.96
is obtained as the instability threshold above which plates depart from their initial
equilibrium position. The progressive streamlining of the trailing edge translates into
significant reductions of the associated mean drag coefficients. Thus, reductions close
to 19% with respect to reference static plates configurations are obtained for the most
flexible case of U∗ = 3.48 for both β = 0◦ and β = 4◦. A close inspection of the
near wake reveals that the inwards progressive mean displacement of the plates yields
a reduction in the recirculation bubble size. A symmetric evolution of the recirculating
bubble is observed for β = 0◦, whereas the bubble becomes asymmetric for β = 4◦,
with a larger leeward clockwise vortex. In both cases, the drag coefficient is shown
to vary linearly with the global aspect ratio of the recirculating bubble. The analysis
of the numerical results shows that the reduced extension of the recirculating bubble
significantly alters the formation length and intensity of the eddies size and associated
pressure. It is observed that despite the local pressure decrease in the vortices shed from
the trailing edges, the plates self adaption reduces their size and prevents the eddies
from entering the cavity, thus, creating a dead flow region with a consequent pressure
increase at the body base.Junta de Andalucia FEDER-UJA 1262764Universidad de JaenEuropean CommissionSpanish MCIN/AEI PDC2021-121288-I00European Union Next Generation EU/PRT
TOI-1468: a system of two transiting planets, a super-Earth and a mini-Neptune, on opposite sides of the radius valley
We report the discovery and characterization of two small transiting planets orbiting the bright M3.0 V star TOI-1468 (LSPM J0106+1913), whose transit signals were detected in the photometric time series in three sectors of the TESS mission. We confirm the planetary nature of both of them using precise radial velocity measurements from the CARMENES and MAROON-X spectrographs, and supplement them with ground-based transit photometry. A joint analysis of all these data reveals that the shorter-period planet, TOI-1468 b (P_(b) = 1.88 d), has a planetary mass of M_(b) = 3.21 ± 0.24 M_(ꚛ) and a radius of R_(b) = 1.280^(+0.038)_(−0.039) R_(ꚛ), resulting in a density of ρ_(b) = 8.39^(+1.05)_(−0.92) g cm^(−3) , which is consistent with a mostly rocky composition. For the outer planet, TOI-1468 c (P_(c) = 15.53 d), we derive a mass of M_(c) = 6.64^(+0.67)_(−0.68) M_(ꚛ), a radius of R_(c) = 2.06 ± 0.04 R_(ꚛ), and a bulk density of ρ_(c) = 2.00^(+0.21)_(−0.19) g cm^(−3) , which corresponds to a rocky core composition with a H/He gas envelope. These planets are located on opposite sides of the radius valley, making our system an interesting discovery as there are only a handful of other systems with the same properties. This discovery can further help determine a more precise location of the radius valley for small planets around M dwarfs and, therefore, shed more light on planet formation and evolution scenarios
A nearby transiting rocky exoplanet that is suitable for atmospheric investigation
Spectroscopy of transiting exoplanets can be used to investigate their atmospheric properties and habitability. Combining radial velocity (RV) and transit data provides additional information on exoplanet physical properties. We detect a transiting rocky planet with an orbital period of 1.467 days around the nearby red dwarf star Gliese 486. The planet Gliese 486 b is 2.81 Earth masses and 1.31 Earth radii, with uncertainties of 5%, as determined from RV data and photometric light curves. The host star is at a distance of ~8.1 parsecs, has a J-band magnitude of ~7.2, and is observable from both hemispheres of Earth. On the basis of these properties and the planet’s short orbital period and high equilibrium temperature, we show that this terrestrial planet is suitable for emission and transit spectroscopy
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