Experimental study for the determination of the turbulence onset in natural convection on inclined plates

In June, 8th, 2009 the balloon-borne solar telescope SUNRISE was launched from the Swedish Space Corporation balloon facility Esrange. A telescope with a mirror of 1 m in diameter ob-served the Sun during six days until the mission was terminated in Canada. The design process of SUNRISE and of any optical telescope requires the analysis of the effect of surrounding air on the quality of images. The turbulence encountered in the local telescope environment de-grades its optical performance. This phenomenon called `seeing' consists of optical aberrations produced by density non-homogeneities in the air along the optical path. The refraction index of air changes due to thermal non-uniformities so that the wavefront incident on the mirror is randomly distorted, and therefore, images are altered. When telescope mirrors are heated, as it happens in solar telescopes, and therefore they are at a temperature different from the environment's, natural convection occurs. It is then crucial to know whether the flow in front of the mirror is laminar or turbulent. After reviewing the literature, it was found that the scattering of results about the onset of the transition gives only rough orders of magnitude of the values of the critical Grashof numbers. Aiming to obtain more information about it, the problem of determination of the turbulence onset in natural convection on heated inclined plates in air environment was experimentally revisited. The transition has been determined from hot wire velocity measurements. The onset of turbulence has been considered to take place where velocity perturbations start to grow. Experiments have shown that the onset depends not only on the Grashof number, but also on other parameters as the temperature difference between the heated plate and the surrounding air. A correlation between dimensionless Grashof and Reynolds numbers has been obtained, fitting extraordinarily well the experimental data. The results are obtained in terms of non-dimensional numbers, this way they apply to any air pressure and therefore to any floating altitud

On the onset of turbulence in natural convection on inclined plates

The problem of determination of the turbulence onset in natural convection on heated inclined plates in an air environment has been experimentally revisited. The transition has been detected by using hot wire velocity measurements. The onset of turbulence has been considered to take place where velocity fluctuations (measured through turbulence intensity) start to grow. Experiments have shown that the onset depends not only on the Grashof number defined in terms of the temperature difference between the heated plate and the surrounding air. A correlation between dimensionless Grashof and Reynolds numbers has been obtained, fitting quite well the experimental data

Galloping instabilities of Z-shaped shading louvers

Modern design of civil constructions such as office blocks, airport terminal buildings, factories, etc. incorporates more and more environmental considerations that lead to, amongst other elements, the use of glazed façades with shading devices to optimize energy consumption. These shading devices, normally slats or louvers, are very flexible structures exposed to the action of wind, and therefore aeroelastic effects such as galloping must be taken into account in their design. A typical cross-section for such elements is a Z-shaped profile made out of a central web and two side wings. The results of a parametric analysis based on static wind tunnel tests and performed on different Z-shaped louvers to determine translational galloping instability regions are presented in this paper

Experimental determination of the onset of turbulence on inclined plates using hot wire velocity measurements

The problem of determination of the turbulence onset in natural convection on heated inclined plates in an air environment has been experimentally revisited. The transition has been detected by using hot wire velocity measurements. The onset of turbulence has been considered to take place where velocity fluctuations (measured through turbulence intensity) start to grow. Experiments have shown that the distance to the plate edge where the onset begins depends both on the plate inclination angle and the plate temperature, and thus on the Grashof number defined in terms of the temperature difference between the heated plate and the surrounding air. An experimental setup to measure the above mentioned distance has been developed. In this paper, such an apparatus is presented, as well as the experimental procedure and some experimental results

Influencia del consumo moderado de cerveza sobre la toxicocinética del aluminio: estudio agudo

Objective: Aluminium has lately been implicated as one of the possible causal factors contributing to Alzheimer's disease and other neurodegenerative disorders due to this metal is conducive to oxidative stress in the brain. According to different researches, it has been suggested that silicon may interfere in the toxico-kinetic of this metal. The present study has examined the effect of beer consumption as a source of silicon on the bioavailability of aluminium and the possible role of beer consumption in averting aluminium's neurotoxicity. Material and methods: In a three-day study, male rats were subjected to acute exposure to aluminium while being given two types of beer, i.e., alcoholic and non-alcoholic beer, to drink at two intake levels, one equivalent to moderate to low consumption in humans (0.5 I/d; 27.5 g alcohol/d) and another equivalent to moderate to high consumption in humans (1 I/d; 55 g alcohol/day). Aluminium and silicon were determined by ICP-MS and ICPOES, respectively. Results: The results obtained seem indicate that at moderately high levels of alcoholic beer intake the silicon present in the beer was able to reduce aluminium uptake in the digestive tract, increasing its excretion by faecal route. In addition, a possible interaction of both elements at level of distribution and renal excretion is suggested. Conclusion: In consequence, moderate beer consumption, possibly affording a protective factor for the toxic effect of aluminium, one of the environmental factors for Alzheimer's disease

Role of beer as a possible protective factor in preventing Alzheimer's disease

Aluminium (Al), a neurotoxin, has lately been implicated as one of the possible causal factors contributing to Alzheimer's disease. Because silicon (Si) intake can affect the bioavailability of aluminium, the object of the present study was to assess whether moderate beer consumption might, as a source of dietary Si, affect the toxicokinetics of Al and thereby limit that element's neurotoxicity. The results obtained confirmed that at moderately high levels of beer intake the Si present in the beer was able to reduce Al uptake in the digestive tract and thus was able to slow the accumulation of this metal in the body, brain tissue included. In consequence, moderate beer consumption, due to its content in bioavailability silicon, possibly affording a protective factor for preventing Alzheimer's disease, could perhaps be taken into account as a component of the dietary habits of the population

Delamination Study in Edge Trimming of Basalt Fiber Reinforced Plastics (BFRP)

[EN] Although there are many machining studies of carbon and glass fiber reinforced plastics, delamination and tool wear of basalt fiber reinforced plastics (BFRP) in edge trimming has not yet studied. This paper presents an end milling study of BFRP fabricated by resin transfer molding (RTM), to evaluate delamination types at the top layer of the machined edge with different cutting conditions (cutting speed, feed rate and depth of cut) and fiber volume fraction (40% and 60%). This work quantifies delamination types, using a parameter Sd/L, that evaluates the delamination area (Sd) and the length (L), taking into account tool position in the yarn and movement of yarns during RTM process, which show the random nature of delamination. Delamination was present in all materials with 60% of fiber volume. High values of tool wear did not permit to machine the material due to an excessive delamination. Type II delamination was the most usual delamination type and depth of cut has influence on this type of delamination.The authors gratefully acknowledge the funding by the Ministerio de Educacion y Ciencia of the Spanish government under grant DPI2013-44903-R-AR.Navarro-Mas, M.; García Manrique, JA.; Meseguer, MD.; Ordeig Fernández, IN.; Sánchez Galdón, AI. (2018). Delamination Study in Edge Trimming of Basalt Fiber Reinforced Plastics (BFRP). Materials. 11(8). doi:10.3390/ma1108141811

Monitoring heavy metal contents in food and hair in a sample of young Spanish subjects

For most people the main route Of exposure to the toxic elements is through the diet. Consequently, information concerning dietary intake is of the utmost importance in being able to assess risks to human health. The goal of this study was to intend to assess the usefulness of hair as a biomonitor of the mineral status in young adults. Daily intakes of selected toxic and essential mineral elements were evaluated using a food frequency questionnaire. In addition, the levels of these same elements in hair samples were Measured by inductively Coupled plasma mass spectrometry and inductively coupled plasma atomic emission spectrometry. The contents of the essential elements in the study population were all well above Spanish recommendations for adult males and females. The estimated intakes of toxic elements were appreciably below the respective PTWIs, indicating that these intake levels do not pose a health concern for this group. Significant differences in hair metal levels were observed between the men and the women, who were in the same age group. Interestingly, no correlation was found between trace element intakes and the corresponding levels in the hair. In conclusion, hair is only limited usefulness as a means of estimating the nutritional status of the essential and toxic elements considered

Tool wear study in edge trimming on basalt fibre reinforced plastics

[EN] In machining of reinforced fibre composite parts, abrasive fibres and material heterogeneity produce poor surface finish, delamination and tool wear. In this research, basalt fibre reinforced plastic is machined with edge trimming in order to study tool wear, using a tool holder of diameter 25 mm, with two exchangeable uncoated carbide cutting inserts. Cutting conditions (cutting speed, feed per tooth and depth) and material characteristics (fibre volume fraction and fibre orientation) are evaluated to know their influence in the flank wear (Vb) of the tool. An analysis of variance (ANOVA) was performed to study flank wear and material removal rate, and a generalized linear model (GLM) was developed. More influence variables in the flank wear are the machining conditions, being the tool life suitable for this machining and material.This work was funded by the Research Project DPI2013-44903-R-AR of the MINER.Navarro-Mas, M.; Meseguer, MD.; Sánchez Galdón, AI.; Gutiérrez, SC. (2017). Tool wear study in edge trimming on basalt fibre reinforced plastics. Procedia Manufacturing. 13:259-266. doi:10.1016/j.promfg.2017.09.067S2592661

Milling angular references and process parameters on fiber reinforced plastics

[EN] Machining of fiber-reinforced composites produces delamination in the workpiece. In bidirectional long fiber fabric reinforced composites, delamination depends on different parameters. In this work, two parameters are studied: fiber orientation angle respect to machining direction and the distance of the warp yarn from the trimmed edge until the next dip below the crossing fill. This work defines angles relating fiber orientation with cutting and feed movements and their relations in a robust way, being applied to edge trimming and grooving operations. On the other hand, for Type II delamination, three different kinds of delamination (constant, uniform pattern variation and random) are studied taking into account fiber orientation, wick size and the fiber orientation angle respect to machining direction.Navarro-Mas, M.; Meseguer, M.; Ordeig Fernández, IN.; Lluch-Cerezo, J. (2021). Milling angular references and process parameters on fiber reinforced plastics. IOP Conference Series Materials Science and Engineering. 1193:1-10. https://doi.org/10.1088/1757-899x/1193/1/012004110119