Frente de Defensa de la Amazonía. El juicio a la petrolera Chevron-Texaco

Saludos con todos y todas. Más que hablar de otros elementos quiero contarles algunos de los hechos que vivimos cotidianamente en la Amazonía ecuatoriana. Desde hace más de 25 años trabajo en la Amazonía norte de Ecuador, en lo que hoy son las provincias de Orellana y Sucumbíos. Por mi trabajo en el campo profesional como abogado he estado al frente de litigios, que involucran a distintos pueblos indígenas de la Amazonía ecuatoriana, del ambiente y los Derechos Humanos de quienes vivimos allí. Sin embargo, el caso más importante del que me ha tocado ser parte es el caso de las comunidades indígenas y campesinas, quienes desde hace 18 años atrás venimos sosteniendo en contra de la petrolera Chevron. Litigio que por varias razones se ha convertido en el juicio más importante de la humanidad en la lucha por los derechos humanos y los derechos ambientales

Impact of ultrasoft neutrinos and realistic radial wavefunctions on neutrinoless double-beta decay matrix elements

Universidad de Sevilla. Máster Universitario en Física Nuclea

Influence of flow tree-dimensionality on the heat transfer of a narrow channel backward facing step flows

This manuscript studies the forced-mixed convective flow on a three-dimensional backward facing step with low aspect ratio (AR = 4) and expansion ratio ER = 2 for Reynolds number in the laminar and beginning of transitional regime (Re 100-1200). The analysis is performed using large eddy simulations, with the main objective assessing the effect of sidewalls on heat transfer characteristics on bottom wall in narrow channels with sudden expansion. The numerical model has been validated with experimental and numerical results from the literature and qualitatively with the experimental results obtained through Moire deflectometry. The bottom surface was kept at constant temperature greater than the flow inlet temperature, while the other walls are considered to be adiabatic. To decouple the three-dimensional flow features due to the sidewalls and the intrinsic three-dimensional instabilities of the separated flow, two different boundary conditions on lateral walls, slip and non-slip, have been used. The results obtained show that when slip sidewalls are considered, the three-dimensional intrinsic structures begging to appear for Re equal to 1200. These structures enhance the heat transfer in the bottom wall. On the contrary, with non-slip sidewalls, the strong three-dimensional structures caused by the sidewalls represented by the upper side recirculation bubble and the wall jets mask the intrinsic three-dimensional instability, decreasing the heat transfer in the lower wall downstream of the step. As a consequence, the surface averaged Nusselt for all Reynolds numbers corresponding to the beginning of the transitional flow is lower for the case of non-slip sidewalls than for the case of slip sidewalls. Thus, the study concludes that sidewalls have a negative effect on heat transfer in narrow channels for flow Reynolds numbers in the early transitional regime

Assessment of experimental optical techniques for characterizing heat transfer using numerical simulations

This manuscript addresses the application of numerical simulations for assessing the error in the measurement of the bulk temperature along the laser beam of a 3D flow using a 2D Moire deflectometry analysis. To analyze the effect of different flow parameters on the error, a 3D computational model of an experimental system was developed. The simulated domain represents the well-known solution of the backward facing step in a rectangular channel but includes a hot-plate at the bottom of the step to enhance the heat transfer effects. The geometry resembles that found in a general heat exchanger. The difference between the computed bulk temperature of the flow and the average temperature obtained via the 2D Moire is analytically evaluated for various assumed general temperature profiles; the numerically computed profiles of temperature indicates that the error decreases with the channel aspect ratio. The use of CFD enables the determination of the flow topology and thus an evaluation of the 3D flow behavior that will cause the measurement error. A parametric study was performed for different flow conditions, namely, the aspect ratio of the channel, the inflow conditions (flow velocity or Reynolds number), and the temperature of the hot wall. The results indicate that the Moire technique is suitable for evaluating the bulk temperature in typical heat exchange devices and flow conditions

Assessment of secondary bubble formation on a backward-facing step geometry

Flow visualization experiments and numerical simulations were performed on a narrow three-dimensional backward-facing step (BFS) flow with the main objective of characterizing the secondary bubble appearing at the top wall. The BFS has been widely studied because of its geometrical simplicity as well as its ability to reproduce most of the flow features appearing in many applications in which separation occurs. A BFS test rig with an expansion ratio of 2 and two aspect ratios (AR = 4 and AR = 8) was developed. Tests were performed at range of Reynolds numbers ranging from 50 to 1000; visualization experiments provided a qualitative description of secondary bubble and wall-jet flows. Large eddy simulations were carried out with two different codes for validation. Numerical solutions, once validated with experimental data from the literature, were used to acquire a deeper understanding of the experimental visualizations, to characterize the secondary bubble as a function of the flow variables (Reynolds and AR) and to analyze the effect of the secondary bubble on primary reattachment length. Finally, to decouple the sidewall effects due to the non-slip condition and the intrinsic flow three-dimensionality, numerical experiments with free-slip conditions over the sidewalls were computed. The main differences were as follows: When the non-slip condition is used, the secondary bubble appears at a Reynolds number of approximately 200, increases with the Reynolds number, and is limited to a small part of the span. This recirculation zone interacts with the wall-jets and causes the maximum and minimum lengths in the reattachment line of the primary recirculation. Under free slip conditions, the recirculation bubble appears at a higher Reynolds number and covers the entire channel span. Published by AIP Publishing

Some Results of the Educational Experiment APIS (Cervantes Mission on Board ISS)

Some results of the analysis of the pictures taken along the performance of the Análisis de Propiedades Inerciales de Sólidos, Analysis of the Inertia Properties of Solid Bodies (APIS) experiment carried out in the Cervantes mission on board ISS, are presented. APIS was an educational experiment devoted to take advantage of the unique conditions of absence of relative gravity forces of a space platform such as ISS, to show some of the characteristics of the free rotational motion of a solid body, which are impossible to carry out on earth. This field of experimental research has application to aerospace engineering science (e.g. attitude control of spacecrafts), to astrophysical sciences (e.g. state of rotation and tumbling motions of asteroids) and to engineering education. To avoid the effect of the ambient atmosphere loads on the motion, the test body is placed inside a sphere, which reduces the effect of the aerodynamic forces to just friction. The drastic reduction of the effect of the surrounding air during the short duration of the experimental sequences allows us to compare the actual motion with the known solutions for the solid body rotation in vacuum. In this paper, some selected, relevant sequences of the sphere enclosing a body with a nominal cylindrical inertia tensor, put into rotation by the astronaut, are shown; the main problems to extract the information concerning the characteristic parameters of the motion are outlined, and some of the results obtained concerning the motion of the test probe are included, which show what seems to be a curious and unexpected solution of the Euler equations for the solid body rotation in vacuum, without energy dissipation, when the angular momentum is almost perpendicular to the axisymmetry axis

Influence of geometrical parameters on the linear stability of a Benard-Marangoni problem

[EN] A linear stability analysis of a thin liquid film flowing over a plate is performed. The analysis is performed in an annular domain when momentum diffusivity and thermal diffusivity are comparable (relatively low Prandtl number, Pr = 1.2). The influence of the aspect ratio (Gamma) and gravity, through the Bond number (Bo), in the linear stability of the flow are analyzed together. Two different regions in the Gamma-Bo plane have been identified. In the first one the basic state presents a linear regime (in which the temperature gradient does not change sign with r). In the second one, the flow presents a nonlinear regime, also called return flow. A great diversity of bifurcations have been found just by changing the domain depth d. The results obtained in this work are in agreement with some reported experiments, and give a deeper insight into the effect of physical parameters on bifurcations.The computations shown in this work were made possible by a generous grant of computer time from the supercomputation center of the Universitat Politecnica de Valencia.Hoyas, S.; Fajardo, P.; Pérez Quiles, MJ. (2016). Influence of geometrical parameters on the linear stability of a Benard-Marangoni problem. Physical Review E. 93(4). https://doi.org/10.1103/PhysRevE.93.043105S934Bénard, H. (1901). Les tourbillons cellulaires dans une nappe liquide. - Méthodes optiques d’observation et d’enregistrement. Journal de Physique Théorique et Appliquée, 10(1), 254-266. doi:10.1051/jphystap:0190100100025400Smith, M. K., & Davis, S. H. (1983). Instabilities of dynamic thermocapillary liquid layers. Part 1. Convective instabilities. Journal of Fluid Mechanics, 132, 119-144. doi:10.1017/s0022112083001512Garnier, N., & Chiffaudel, A. (2001). Two dimensional hydrothermal waves in an extended cylindrical vessel. The European Physical Journal B, 19(1), 87-95. doi:10.1007/s100510170352Hoyas, S., Herrero, H., & Mancho, A. M. (2002). Bifurcation diversity of dynamic thermocapillary liquid layers. Physical Review E, 66(5). doi:10.1103/physreve.66.057301Hoyas, S., Herrero, H., & Mancho, A. M. (2002). Thermal convection in a cylindrical annulus heated laterally. Journal of Physics A: Mathematical and General, 35(18), 4067-4083. doi:10.1088/0305-4470/35/18/306Hoyas, S., Mancho, A. M., Herrero, H., Garnier, N., & Chiffaudel, A. (2005). Bénard–Marangoni convection in a differentially heated cylindrical cavity. Physics of Fluids, 17(5), 054104. doi:10.1063/1.1876892Herrero, H., & Mancho, A. M. (1998). Influence of aspect ratio in convection due to nonuniform heating. Physical Review E, 57(6), 7336-7339. doi:10.1103/physreve.57.7336Mancho, A., Herrero, H., & Burguete, J. (1997). Primary instabilities in convective cells due to nonuniform heating. Physical Review E, 56(3), 2916-2923. doi:10.1103/physreve.56.2916Ezersky, A. B., Garcimartín, A., Burguete, J., Mancini, H. L., & Pérez-García, C. (1993). Hydrothermal waves in Marangoni convection in a cylindrical container. Physical Review E, 47(2), 1126-1131. doi:10.1103/physreve.47.1126Hoyas, S., Gil, A., Fajardo, P., & Pérez-Quiles, M. J. (2013). Codimension-three bifurcations in a Bénard-Marangoni problem. Physical Review E, 88(1). doi:10.1103/physreve.88.015001Peng, L., Li, Y.-R., Shi, W.-Y., & Imaishi, N. (2007). Three-dimensional thermocapillary–buoyancy flow of silicone oil in a differentially heated annular pool. International Journal of Heat and Mass Transfer, 50(5-6), 872-880. doi:10.1016/j.ijheatmasstransfer.2006.08.015Shi, W., Liu, X., Li, G., Li, Y.-R., Peng, L., Ermakov, M. K., & Imaishi, N. (2010). Thermocapillary Convection Instability in Shallow Annular Pools by Linear Stability Analysis. Journal of Superconductivity and Novel Magnetism, 23(6), 1185-1188. doi:10.1007/s10948-010-0661-8Torregrosa, A. J., Hoyas, S., Pérez-Quiles, M. J., & Mompó-Laborda, J. M. (2013). Bifurcation Diversity in an Annular Pool Heated from Below: Prandtl and Biot Numbers Effects. Communications in Computational Physics, 13(2), 428-441. doi:10.4208/cicp.090611.170212aEckert, E. R. G., Goldstein, R. J., Ibele, W. E., Patankar, S. V., Simon, T. W., Kuehn, T. H., … Garrick, S. (2000). Heat transfer — a review of 1997 literature. International Journal of Heat and Mass Transfer, 43(14), 2431-2528. doi:10.1016/s0017-9310(99)00196-9Hoyas, S., Fajardo, P., Gil, A., & Perez-Quiles, M. J. (2014). Analysis of bifurcations in a Bénard–Marangoni problem: Gravitational effects. International Journal of Heat and Mass Transfer, 73, 33-41. doi:10.1016/j.ijheatmasstransfer.2014.01.061O’Shaughnessy, S. M., & Robinson, A. J. (2013). Heat transfer near an isolated hemispherical gas bubble: The combined influence of thermocapillarity and buoyancy. International Journal of Heat and Mass Transfer, 62, 422-434. doi:10.1016/j.ijheatmasstransfer.2013.02.064Celli, M., Barletta, A., & Alves, L. S. de B. (2015). Marangoni instability of a liquid film flow with viscous dissipation. Physical Review E, 91(2). doi:10.1103/physreve.91.023006Orszag, S. A. (1972). Comparison of Pseudospectral and Spectral Approximation. Studies in Applied Mathematics, 51(3), 253-259. doi:10.1002/sapm1972513253Canuto, C., Hussaini, M. Y., Quarteroni, A., & Zang, T. A. (1988). Spectral Methods in Fluid Dynamics. doi:10.1007/978-3-642-84108-8JIMÉNEZ, J., & HOYAS, S. (2008). Turbulent fluctuations above the buffer layer of wall-bounded flows. Journal of Fluid Mechanics, 611, 215-236. doi:10.1017/s0022112008002747Mancho, A. M., & Herrero, H. (2000). Instabilities in a laterally heated liquid layer. Physics of Fluids, 12(5), 1044-1051. doi:10.1063/1.870359Favre, E., Blumenfeld, L., & Daviaud, F. (1997). Instabilities of a liquid layer locally heated on its free surface. Physics of Fluids, 9(5), 1473-1475. doi:10.1063/1.869470Burguete, J., Mukolobwiez, N., Daviaud, F., Garnier, N., & Chiffaudel, A. (2001). Buoyant-thermocapillary instabilities in extended liquid layers subjected to a horizontal temperature gradient. Physics of Fluids, 13(10), 2773-2787. doi:10.1063/1.1398536Daviaud, F., & Vince, J. M. (1993). Traveling waves in a fluid layer subjected to a horizontal temperature gradient. Physical Review E, 48(6), 4432-4436. doi:10.1103/physreve.48.4432RILEY, R. J., & NEITZEL, G. P. (1998). Instability of thermocapillary–buoyancy convection in shallow layers. Part 1. Characterization of steady and oscillatory instabilities. Journal of Fluid Mechanics, 359, 143-164. doi:10.1017/s0022112097008343Mercier, J. F., & Normand, C. (1996). Buoyant‐thermocapillary instabilities of differentially heated liquid layers. Physics of Fluids, 8(6), 1433-1445. doi:10.1063/1.868920Yu, J.-J., Ruan, D.-F., Li, Y.-R., & Chen, J.-C. (2015). Experimental study on thermocapillary convection of binary mixture in a shallow annular pool with radial temperature gradient. Experimental Thermal and Fluid Science, 61, 79-86. doi:10.1016/j.expthermflusci.2014.10.01

Experimental assessment of RANS models for wind load estimation over solar-panel arrays

This article belongs to the Special Issue Application of Computational Fluid Dynamics in Mechanical EngineeringThis paper reports a comparison between wind-tunnel measurements and numerical simulations to assess the capabilities of Reynolds-Averaged Navier-Stokes models to estimate the wind load over solar-panel arrays. The free airstream impinging on solar-panel arrays creates a complex separated flow at large Reynolds number, which is severely challenging for the current Reynolds-Averaged Navier-Stokes models. The Reynolds-Averaged Navier-Stokes models compared in this article are k-ϵ, Shear-Stress Transport k-ω, transition and Reynolds Shear Model. Particle Image Velocimetry measurements are performed to investigate the mean flow-velocity and turbulent-kinetic-energy fields. Pressure taps are located in the surface of the solar panel model in order to obtain static pressure measurements. All the Reynolds-Averaged Navier-Stokes models predict accurate average velocity fields when compared with the experimental ones. One of the challenging factor is to predict correctly the thickness of the turbulent wake. In this aspect, Reynolds Shear provides the best results, reproducing the wake shrink observed on the 3rd panel in the experiment. On the other hand, some other features, most notably the blockage encountered by the flow below the panels, are not correctly reproduced by any of the models. The pressure distributions over the 1st panel obtained from the different Reynolds-Averaged Navier-Stokes models show good agreement with the pressure measurements. However, for the rest of the panels Reynolds-Averaged Navier-Stokes fidelity is severely challenged. Overall, the Reynolds Shear model provides the best pressure estimation in terms of pressure difference between the front and back sides of the panels.The authors wish to thanks Carlos Cobos for contributing the realisation of the experimental setup and J. Rodríguez for providing the PIV system. The authors acknowledge S. Discetti and A. Ianiro for insightful comments and discussions

Set-up analysis and Optimization of CFD Simulations for Radial Turbines

[EN] This paper proposes a CFD method for simulating radial turbocharger turbine flows. A review is presented of the computational model in terms of meshing, mesh movement strategy, and computational algorithm in turbomachinery CFD simulations. A novel local mesh independence analysis is developed for this purpose. This procedure is aimed at distributing the cells more efficiently by selecting suitable cell sizes for the different regions of the domain to optimize the use of the available computational resources. Pressure- and density-based solvers are compared. The influence of the moving-mesh strategy was analyzed, and small differences were observed in the region near the maximum efficiency point, while these differences increased when off-design conditions were considered. Finally, a comparison of the results with data from an experimental test bench shows that the proposed computational methodology can be used to characterize radial turbomachinery. The objective of the analysis and the optimization of the case configuration was to establish some general guidelines for CFD turbomachinery simulations.The authors are indebted to the Spanish Ministerio de Econom a y Competitividad through Project TRA 2010-16205.Galindo, J.; Hoyas, S.; Fajardo, P.; Navarro, R. (2013). Set-up analysis and Optimization of CFD Simulations for Radial Turbines. Engineering Applications of Computational Fluid Mechanics. 7(4):441-460. doi:10.1080/19942060.2013.11015484S44146074ANSYS (2009).Ansys Fluent 12.0 User’s Guide. Canonsburg, PA: ANSYS Inc.ANSYS (2011).ANSYS FLUENT Theory Guide. ANSYS Inc.Aymanns R, Scharf J, Uhlmann T, Lückmann D (2011). A revision of quasi steady modelling of turbocharger turbines in the simulation of pulse charged engines.16th Supercharging Conference.Hellström F (2010).Numerical Computations of the Unsteady Flow in Turbochargers. PhD thesis, Royal Institute of Technology KTH Fluid Physics.Hiereth H, Prenninger P (2007).Charging the Internal Combustion Engine. Springer Verlag.Japikse D, Baines NC (1997).Introduction to Turbomachinery. Oxford University Press.Liu Z, Hill DL (2000). Issues surrounding multiple frames of reference models for turbo compressor applications.Fifteenth International Compressor Engineering Conference, Purdue University, USA

A moving mesh generation strategy for solving an injector internal flow problem

[EN] The ability to handle complex geometries is an important part of transient calculations; therefore, the need for fully automatic mesh generation capable of dealing with such geometries is quite demanded. In this paper a specific approach to fully automatic three-dimensional mesh generation is presented. An approach to moving the generated mesh is also outlined. In particular, the simulation of a diesel injector needle movement is sought. The movement of the needle was calculated on the basis of injection rate experimental data and injection rate predicted data with steady state boundaries and geometry. The simulation was performed using the commercial code STAR-CD version 4.06. (C) 2010 Elsevier Ltd. All rights reserved.This research was funded by the Spanish Government in the framework of the Project "Caracterizacion experimental de la cavitacion en el flujo interno e influencia sobre modelos de chorro Diesel'', Reference TRA2007-68006-C02-01. SH and PF were partially supported by the Universidad Politecnica de Valencia under the program "Primeros Proyectos de investigacion'', in the framework of the project "Simulacion CFD de chorros Diesel en inyeccion directa: la atomizacion primaria'', Reference PAID-2759.Margot, X.; Hoyas, S.; Fajardo, P.; Patouna, S. (2010). A moving mesh generation strategy for solving an injector internal flow problem. Mathematical and Computer Modelling. 52:1143-1150. doi:10.1016/j.mcm.2010.03.018S114311505