Search results for "REY"

A study of turbulent heat transfer in curved pipes by numerical simulation

2013

Abstract Turbulent heat transfer in curved pipes was studied by numerical simulation. Two curvatures δ (pipe radius a/curvature radius c) were considered, 0.1 and 0.3; results were also obtained for a straight pipe (δ = 0) for comparison purposes. A tract of pipe 5 diameters in length was chosen as the computational domain and was discretized by finite volume multiblock-structured grids of ∼5.3 × 106 hexahedral cells. Fully developed conditions were assumed; the friction velocity Reynolds number was 500, corresponding to bulk Reynolds numbers between 12 630 and ∼17 350 according to the curvature, while the Prandtl number was 0.86 (representative of saturated liquid water at 58 bar). Simulat…

An experimental investigation on natural convection of air in a vertical channel

1993

Abstract The free convection of air in a vertical channel is studied experimentally in a laboratory model of height H = 2.6 m and rectangular cross-section b × s , with b = 1.2 m and the channel width s variable. One of the channel walls is heated with a uniform heat flux. Tests are made with different values of channel gap and heating power ( s = 7.5, 12.5, 17 cm; q c = 48–317 W m −2 ). On the basis of the results two empirical formulae are found, giving Nu and Re as functions of Ra and the geometrical parameter s/H ; Nu = 0.9282 Ra 0.2035 (s/H) 0.8972 ; Re = 0.5014 Ra 0.3148 (s/H) 0.418 . The mathematical form of these relationships reproduces other previously published formulae, valid fo…

Investigation of flow and heat transfer in corrugated passages—I. Experimental results

1996

Abstract An experimental and numerical study of flow and heat transfer was conducted for a crossed-corrugated geometry, representative of compact heat exchangers including air preheaters for fossil-fuelled power plant. In this paper, we describe the method of applying thermochromic liquid crystals and true-colour image processing to give local Nusselt number distribution over the surface, and average Nu, both of quantitative reliability; a careful uncertainty analysis is also presented. Typical experimental results for heat transfer and pressure drop are presented and discussed for various geometries and Reynolds numbers, and are compared with literature data. Numerical predictions are disc…

Numerical observations of turbulence structure modification in channel flow over 2D and 3D rough walls

2015

Abstract The effects of wall roughness on turbulence structure modifications were explored by numerical experiments, carried out using Large Eddy Simulation techniques. The wall geometry was made using an archetypal artificial method, thus to achieve irregular two- and three-dimensional shapes. The proposed roughness shapes are highly irregular and are characterised by high and small peaks, thus it can be considered a practical realistic roughness. Their effects are analysed comparing the turbulence quantities over smooth, 2D and 3D rough walls of fully developed channel flow at relatively low friction Reynolds number Re τ = 395 . Both transitional and fully rough regimes have been investig…

Response of an arctic predator guild to collapsing lemming cycles

2012

6 pages; International audience; Alpine and arctic lemming populations appear to be highly sensitive to climate change, and when faced with warmer and shorter winters, their well-known high-amplitude population cycles may collapse. Being keystone species in tundra ecosystems, changed lemming dynamics may convey significant knock-on effects on trophically linked species. Here, we analyse long-term (1988-2010), community-wide monitoring data from two sites in high-arctic Greenland and document how a collapse in collared lemming cyclicity affects the population dynamics of the predator guild. Dramatic changes were observed in two highly specialized lemming predators: snowy owl and stoat. Follo…

Influence of fish aggregating devices (FADs) on anti-predator behaviour within experimental mesocosms

2015

Commercial fishers have used fish aggregating devices throughout the Mediterranean Sea for over 40 years. These devices attract numerous predatory and forage species in both coastal and offshore environments. This study examined the influence of fish aggregating devices on schooling and aggregating behaviour by small forage fish in quasi-natural mesocosms. Anti-predator behaviour was evaluated for juvenile Caranx crysos under a variety of treatment conditions. Results suggest that, in the absence of physical structure, C. crysos first respond to a predatory threat by forming a school. When a physical structure is present, however, C. crysos show an occasional tendency to aggregate near the …

Bio-predictive tablet disintegration: Effect of water diffusivity, fluid flow, food composition and test conditions

2013

Abstract Food intake may delay tablet disintegration. Current in vitro methods have little predictive potential to account for such effects. The effect of a variety of factors on the disintegration of immediate release tablets in the gastrointestinal tract has been identified. They include viscosity of the media, precipitation of food constituents on the surface of the tablet and reduction of water diffusivity in the media as well as changes in the hydrodynamics in the surrounding media of the solid dosage form. In order to improve the predictability of food affecting the disintegration of a dosage form, tablet disintegration in various types of a liquefied meal has been studied under stati…

Chers Rois mages

2006

Se trata de la versión francesa del artículo "Carta a los Reyes Magos", publicado en "El País" el 31 de diciembre de 2005.

Carta a los Reyes Magos

2005

Reactions in Spain to the expulsion of the Jesuits from France

1996

Los sucesos que afectaron a los jesuitas en Portugal y Francia fueron seguidos con curiosidad e interés en los ambientes cultos españoles. A través de la correspondencia cruzada entre Gregorio Mayans y diversos personajes, entre los que se encontraban el obispo Asensio Sales, el bibliotecario real Martínez Pingarrón, y el jesuita P. Juan Bautista Gener, y otros, se analizan las actitudes de simpatía o antipatía que suscitaban las medidas antijesuíticas y la gestación de un ambiente proclive a la expulsión. Así mismo, se trata de la repercusión de la consulta del Consejo de Castilla sobre los jesuitas franceses exiliados en España, con referencia al eco que produjo en el Provincial de Aquita…