Experimental study of the aerodynamic noise radiated by cylinders with different cross-sections and yaw angles

Vortex shedding from cylinders has been extensively studied due to its occurrence in many engineering fields. Many experimental studies reported in the literature focus on the aerodynamics of the vortex shedding process but the literature about the radiated noise is more scarce. The aim of the work presented here is to extend the available noise data. Aero-acoustic wind tunnel tests were carried out using cylinders with different cross-sections: circular, square, rectangular and elliptical. Flow speeds between 20 and 50 m/s were used, corresponding to Reynolds numbers in the range from 1.6×104 to 1.2×105. The dependence of the noise on the yaw angle, flow speed, cross-sectional shape, angle of attack and radiation angle (directivity) is assessed. The results obtained are compared, where possible, with those found in the literature for similar cases. It is intended that the results can be used for the validation and calibration of numerical and empirical aerodynamic noise prediction models

Pasados y presente. Estudios para el profesor Ricardo García Cárcel

Ricardo García Cárcel (Requena, 1948) estudió Historia en Valencia bajo el magisterio de Joan Reglà, con quien formó parte del primer profesorado de historia moderna en la Universidad Autónoma de Barcelona. En esta universidad, desde hace prácticamente cincuenta años, ha desarrollado una extraordinaria labor docente y de investigación marcada por un sagaz instinto histórico, que le ha convertido en pionero de casi todo lo que ha estudiado: las Germanías, la historia de la Cataluña moderna, la Inquisición, las culturas del Siglo de Oro, la Leyenda Negra, Felipe II, Felipe V, Austrias y Borbones, la guerra de la Independencia, la historia cultural, los mitos de la historia de España... Muy pocos tienen su capacidad para reflexionar, ordenar, analizar, conceptualizar y proponer una visión amplia y llena de matices sobre el pasado y las interpretaciones historiográficas. A su laboriosidad inimitable se añade una dedicación sin límites en el asesoramiento de alumnos e investigadores e impulsando revistas, dosieres, seminarios o publicaciones colectivas. Una mínima correspondencia a su generosidad lo constituye este volumen a manera de ineludible agradecimiento

Spatiotemporal Characteristics of the Largest HIV-1 CRF02_AG Outbreak in Spain: Evidence for Onward Transmissions

Background and Aim: The circulating recombinant form 02_AG (CRF02_AG) is the predominant clade among the human immunodeficiency virus type-1 (HIV-1) non-Bs with a prevalence of 5.97% (95% Confidence Interval-CI: 5.41–6.57%) across Spain. Our aim was to estimate the levels of regional clustering for CRF02_AG and the spatiotemporal characteristics of the largest CRF02_AG subepidemic in Spain.Methods: We studied 396 CRF02_AG sequences obtained from HIV-1 diagnosed patients during 2000–2014 from 10 autonomous communities of Spain. Phylogenetic analysis was performed on the 391 CRF02_AG sequences along with all globally sampled CRF02_AG sequences (N = 3,302) as references. Phylodynamic and phylogeographic analysis was performed to the largest CRF02_AG monophyletic cluster by a Bayesian method in BEAST v1.8.0 and by reconstructing ancestral states using the criterion of parsimony in Mesquite v3.4, respectively.Results: The HIV-1 CRF02_AG prevalence differed across Spanish autonomous communities we sampled from (p < 0.001). Phylogenetic analysis revealed that 52.7% of the CRF02_AG sequences formed 56 monophyletic clusters, with a range of 2–79 sequences. The CRF02_AG regional dispersal differed across Spain (p = 0.003), as suggested by monophyletic clustering. For the largest monophyletic cluster (subepidemic) (N = 79), 49.4% of the clustered sequences originated from Madrid, while most sequences (51.9%) had been obtained from men having sex with men (MSM). Molecular clock analysis suggested that the origin (tMRCA) of the CRF02_AG subepidemic was in 2002 (median estimate; 95% Highest Posterior Density-HPD interval: 1999–2004). Additionally, we found significant clustering within the CRF02_AG subepidemic according to the ethnic origin.Conclusion: CRF02_AG has been introduced as a result of multiple introductions in Spain, following regional dispersal in several cases. We showed that CRF02_AG transmissions were mostly due to regional dispersal in Spain. The hot-spot for the largest CRF02_AG regional subepidemic in Spain was in Madrid associated with MSM transmission risk group. The existence of subepidemics suggest that several spillovers occurred from Madrid to other areas. CRF02_AG sequences from Hispanics were clustered in a separate subclade suggesting no linkage between the local and Hispanic subepidemics

Component-based model to predict aerodynamic noise from high-speed trains

The aerodynamic noise produced by train pantographs and bogies is significant for typical speeds of modern high-speed trains. In order to reduce the negative environmental impact of high-speed train noise, the aerodynamic noise should be tackled in an early stage of the train design. In recent years, Computational Fluid Dynamics (CFD) and Computational AeroAcoustics (CAA) models have been developed in order to predict aerodynamic noise but they are very computationally-intensive. In this thesis, a semi-empirical component-based model is developed for quick prediction of the aerodynamic noise radiated by a high-speed train pantograph and bogie. The overall noise from the pantograph and bogie is obtained as the incoherent sum of the contributions predicted from the individual components. The model empirical constants are obtained using an experimental database built from data found in the literature and noise tests carried out during this work to evaluate the effect of different geometries and inflow conditions. For the pantograph, the struts are approximated as cylinders with a particular cross-section. To extend the available database, anechoic wind tunnel noise tests were carried out using cylinders with different cross-sections for different configurations. The predictions are compared with available noise measurements using a full-size pantograph showing good agreement. For the bogie case, the prediction model is developed by identifying each of the bogie components with simple shapes. Anechoic wind tunnel noise measurements were carried out using simple shapes to determine the empirical constants of the model. Additionally, scale train car body and bogie mock-ups were used, allowing for model validation and also providing useful information on the dependence on different factors of the aerodynamic noise generation in the bogie region. The results show the potential of the model to be used as an engineering tool to predict aerodynamic noise from train pantographs and bogies, allowing the effect of design modifications of components to be assessed and low-noise technology to be developed. <br/

Uncertainty assessment of a model to predict the vibration induced by train traffic in tunnels

The uncertainty assessment of ground-borne noise and vibration predictions is important to reduce risks when decisions are made based on simulation results. In addition, it provides robustness to the prediction framework that could potentially be used for virtual validation of proposals to reduce noise and vibration induced by railway infrastructures. In this work, a general methodology for prediction uncertainty assessment based on the guide to the expression of uncertainty in measurements is applied to a numerical model dedicated to predict the vibration induced by train traffic in tunnels with slab track with isolated blocks. The standard uncertainty of the predicted acceleration on the tunnel wall is obtained by combining the standard uncertainty of the model inputs: sprung and unsprung axle mass, primary suspension and fasteners stiffness and isolated blocks mass and stiffness. The input uncertainty is defined according to the guidance given in international standards, published work or by experience judgement. The sensitivity factors are obtained as the slope of the function that fits the results obtained by running the simulations for a given range of the input quantities. The proposed methodology provides the uncertainty of the result and the contribution of each input to that uncertaintyPostprint (published version

On the feasibility of a component-based approach to predict aerodynamic noise from high-speed train bogies

At speeds above 300 km/h, aerodynamic noise becomes a significant source of railway noise. In a high-speed train, the bogie area is one of the most important aerodynamic noise sources. To predict aerodynamic noise, semi-empirical component-based models are attractive as they allow fast and cheap calculations compared with numerical methods. Such component-based models have been previously applied successfully to predict the aerodynamic noise from train pantographs which consist of various cylinders. In this work, the feasibility is evaluated of applying them to the aerodynamic noise from bogies, which consist of various bluff bodies. To this end, noise measurements were carried out in an anechoic wind tunnel for different flow speeds using simple shapes representing various idealised components of a bogie. These results have been used to adjust the empirical constants of the component-based prediction model to enable its application to the bogie case. In addition, the noise from a 1:10 scale simplified bogie mock-up was measured and used for comparison with the prediction model. The results show good agreement between measurements and predictions for the bogie alone. When the bogie is located between two ramps approximating a simplified bogie cavity the noise is underpredicted at low frequencies. This is attributed to the noise from the cavity which is not included in the model

Experimental study of the aerodynamic noise radiated by cylinders with different cross-sections and yaw angles

This dataset reports data for the figures published in: E. Latorre Iglesias, D. Thompson and M. Smith &quot;Experimental study of the aerodynamic noise radiated by cylinders with different cross-sections and yaw angles&quot;, Journal of Sound and Vibration, 2015.</span