On the effect of low blowing ratio continuous jets on wingtip vortex characteristics

Vortices are an unavoidable effect of flight, which appear behind the wing with a bounded length. The strength of these vortices, which are extremely stable, is due to the lift force [1]. That is the reason why this phenomenon is especially relevant during take-off and landing operations. In these situations, when aircraft are departing from or arriving to the airport runways, the following aircraft might feel two counter-rotating vortices which remain long time under normal environmental conditions. Unfortunately, this huge rotation of airflow patterns always destabilizes the following aircraft. Consequently, trailing vortices have a mighty influence on the air traffic control of airport runways, and they have justified the research interest in this topic since the 1960's [2]. However, aeronautical engineers are still searching for different technological strategies to breakdown these wingtip vortices.Short-Term Postdoctoral Stay of Talent Attraction Plan of Andalucía TECH ICE. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Nonlinear evolution of harmonically forced perturbations on a wingtip vortex

Wingtip vortices are created by flying airplanes due to lift generation. The vortex interaction with the trailing aircraft has sparked researchers’ interest to develop an efficient technique to destroy these vortices. Different models have been used to describe the vortex dynamics and they all show that, under real flight conditions, the most unstable modes produce a very weak amplification. Another linear instability mechanism that can produce high energy gains in short times is due to the non-normality of the system. Recently, it has been shown that these non-normal perturbations also produce this energy growth when they are excited with harmonic forcing functions. In this study, we analyze numerically the nonlinear evolution of a spatially, pointwise and temporally forced perturbation, generated by a synthetic jet at a given radial distance from the vortex core. This type of perturbation is able to produce high energy gains in the perturbed base flow (10^3), and is also a suitable candidate for use in engineering applications. The flow field is solved for using fully nonlinear three-dimensional direct numerical simulation with a spectral multidomain penalty method model. Our novel results show that the nonlinear effects are able to produce locally small bursts of instability that reduce the intensity of the primary vortex.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

La segmentación del mercado laboral colombiano en la década de los noventa

En este artículo se muestra que las ecuaciones de Mincer, ampliadas con variables de tamaño de las empresas y corregidas por sesgo de selectividad, dan resultados que concuerdan con las teorías del capital humano y de la segmentación. Mayores dotaciones de capital humano y de capital físico de las empresas se relacionan con mayores ingresos de los trabajadores, un resultado compatible con la existencia de economías a escala y con la segmentación entre sectores económicos debido a las barreras del mercado de capital físico y humano

La segmentación del mercado laboral colombiano en la década de los noventa

This article shows that the Mincer equations, augmented with variables of firm size and corrected by selectivity bias, yield results that are consistent with the theories of human capital and labor segmentation. Greater firm endowments of human capital and physical capital are related to greater labor income. This result is consistent with scale economies at the firm level. It also implies divisions between economic sectors due to physical and human capital markets barriers.labor market, Mincer equations, human capital

PIV measurements of the effect of pulsed blowing jet on a NACA0012 wing model

Wingtip vortices are present in taking off, and landing operations and their presence in airport runways must be reduced. To that end, several strategies have been considered in the last decades, being the active control one possible technical solution. To compute the effectiveness of active control that corresponds to pulsed low-blowing-ratio transverse jet for the reduction of the wingtip vortex strength, we carry out 2D-PIV measurements in a towing tank for chord-based Reynolds numbers 15000 and 20000. We consider two cases: (i) no active control Rjet=0 and (ii) pulsating radial jet of blowing-ratio Rjet smaller than 1.7 (or momentum coefficient lower than 0.12) and different Strouhal numbers ranging from 0.27 to 0.94. Our observations show that the best reduction of wingtip vortex strength takes place at the lowest Strouhal number tested. We use the maximum azimuthal velocity and vorticity together with the circulation to quantify this decrease in the vortex strength. Besides, we define the spatial evolution of a disturbance parameter which allow us to detect again the optimal frequency that leads to vortex destruction.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Influence of Reynolds number on theoretical models for trailing vortices

We conduct direct numerical simulations for a NACA0012 airfoil at Reynolds numbers (Re) ranging from 300 to 7000 to determine the wake behavior behind this wing profile. We characterize the structure of the wing-tip vortex, finding a reasonable agreement with experimental results at Re=7000. In addition, we model the trailing vortex theoretically, thus obtaining the parameters for Batchelor’s and Moore and Saffman’s models. We compare the results of the best fitting for the axial vorticity and the azimuthal velocity, finding only small discrepancies. The main contribution of this research work is to study the evolution of these theoretical parameters as function of the Reynolds number. We observe that the wake becomes unstable at Re ≈1200, in agreement with previous results. These instabilities in the wake behind the wing produce a change in the trend of theoretical parameters (keywords: vortex dynamics, trailing vortices, theoretical models).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

E-grocery retailing: from value proposition to logistics strategy

This paper develops two frameworks that identify and organise the elements that make up the value proposition and the logistics strategy of grocery pure players. Those frameworks are also applied to see how the elements of both frameworks are related. To identify the key elements and design characteristics, an extensive literature review was conducted. In addition, an exploratory study with five grocery pure players helped connect both frameworks. The value proposition can be classified into ten elements (range, virtual store, order features, area of delivery, sales mode, velocity, time slots, substitutions, returns, and extra services) and the logistics strategy in twelve (warehousing, inventory, procurement, picking, packing, stock out, transport type, transport ownership, consolidation, dispatch time slots, routing, and returned inventory). The case studies underline important differences among the relationships of these elements for intermediaries and independent pure players.Xunta de Galicia | Ref. ED481A-2017/24

Partial oxycombustion-calcium looping hybridisation for CO2 capture in waste-to-energy power plants

The integration of bioenergy and carbon capture and storage (BECCS) presents a great opportunity for power production with global negative CO2 emissions. This work explores a novel synergetic system that integrates membranes, partial biomass oxycombustion and the calcium looping (CaL) process. Polymeric membranes generate oxygen-enriched air (OEA) with an O2 concentration of 40%v/v, which is used for partial oxycombustion of biomass waste. The CO2-enriched flue gas evolves from the waste-to-energy plant to the CaL unit, where CO2 concentration is increased up to 90-95%v/v, ready for purification and sequestration. Compared to only oxycombustion systems, the proposed concept presents fewer technological challenges in retrofitting boilers to waste-to-energy plants. Moreover, this new approach is highly efficient as integrating membranes to produce OEA instead of cryogenic distillation systems significantly reduces energy consumption. A novel integration concept is modelled to evaluate the whole process efficiency and the effect of key parameters on the system performance, such as the temperature of the reactors, the membrane surface area, and the partial oxy-combustion degree. The results show that the novel system has an energy consumption associated with CO2 capture below 4 MJ/kg CO2 (a 31% lower than that for a conventional CaL process), with a higher CO2 capture efficiency than oxycombustion and the CaL process separately. On the other hand, the economic analysis shows a higher CO2 capture cost for the novel configuration than for the typical CaL configuration due to the additional investment cost of the membrane system. Improvements in membrane performance, mainly by increasing its permeance and diminishing the required surface area, would significantly reduce the economic cost of this novel integration. Using membranes with permeance over 400 GPU would boost the competitiveness of the system.Este ítem es la versión preprint del artículo. Se puede consultar la versión final aquí https://doi.org/10.1016/j.jclepro.2023.136776Junta de Andaluci

Juegos Panamericanos 2011: Comunidad local y su percepción sobre posibles impactos sociales

Tesis para la obtención del título de licenciado en turismoLa importancia del turismo deportivo, especialmente en aspectos económicos, sociales, ambientales y políticos, ha sido un factor muy significativo para convertirse en objeto de estudio. Por tal razón, revistas especializadas han sido establecidas; de igual manera se han llevado a cabo congresos y conferencias dedicadas al estudio de esta tipología de turismo (Ritchie y Adair, 2002). Hoy en día hay una gran tendencia hacia los estudios de eventos deportivos en cuestiones económicas. La mayoría de los estudios de turismo deportivo y sus impactos han sido realizados en países de sociedades avanzadas, tales como el Reino Unido, Canadá, Estados Unidos, Australia, entre otras, descuidando así las implicaciones de dicho fenómeno en países en vías de desarrollo. En este contexto, el presente trabajo muestra los resultados de una investigación sobre el turismo deportivo que tuvo como objetivo identificar los posibles impactos sociales de los Juegos Panamericanos 2011 en la comunidad local a partir de la percepción de sus residentes

Fabrication and characterization of superficially modified porous dental implants

Stress-shielding and loosening compromise the success of dental implants under real-life service conditions. This work evaluates the mechanical behavior of superficially modified porous titanium dental implants fabricated by two different routes: conventional powder metallurgy and space-holder techniques. A novel, feasible and repetitive protocol of micro-milling of the implant thread (before sintering), as well as surface modification treatments (after sintering) are also implemented. The discussion is conducted in terms of the influence of porosity and surface roughness on the stiffness and yield strength of implants. The macro-pores concentrate stress locally, and, at the same time, they could act as a barrier to the propagation of micro-cracks. Higher rugosity was observed for virgin implants obtained with spacer particles. Concerning superficially modified implants, while bioglass 1393 was the most effective coating due to its greater infiltration and adhesion capacity, chemical etching could improve osteoblast adhesion because modifies the roughness of the implant surface.Ministry of Science and Innovation of Spain PID2019-109371GB-I00Junta de Andalucía–FEDER (Spain) US-125977