Experimental analysis of train slipstream in confined spaces

The train slipstream, i.e. the air velocities induced by the train, is one of the most important aerodynamic effects connected to railway vehicles because it has a direct impact on the safety of passengers on the platform and track workers along the railway line. In recent years, a lot of studies were performed to understand the development of this phenomenon in the open field and specific EU standards, the EN 14067-4 and the TSI (Technical Specifications for Interoperability) were issued. On the other hand, only few studies have been carried out to analyze the train passages in confined spaces (as tunnels, line sections with acoustic barriers, etc.), even if the first results of these analyses have shown that the confinement of the air causes more severe conditions regarding the speed of the air flow. This work aims at studying, through a full-scale experimental campaign, the effects of the flow confinement on the air speed caused by the train passage. In particular, the effects of different parameters, linked to the train i.e. the train type and length, the train speed and the measurement position, and linked to the infrastructure i.e. variations in the local infrastructure geometry, were analyzed

Numerical and Experimental Analysis of the Pressure Signature for different High-Speed Trains

This paper describes a procedure for the validation of numerical codes able to reproduce the pressures in tunnel due to the passage of trains. In the first step, the parameters of the numerical code are set by matching the train-tunnel pressure signature measured during a single-passage of different types of train within the tunnel and in the second step, without changing the parameters, the crossing of two trains is simulated. Within the paper, the methodology is applied to the numerical mono-dimensional code DB-Tunnel while the experimental data are those collected during an experimental research programme carried out in the tunnel La Fornace, on the Italian high-speed railway from Roma to Firenze. The accuracy of the numerical code estimation is evaluated in terms of the maximum pressure generated in the tunnel by the train passing/crossing because this is the key parameter, according to the TSI standard for railway infrastructures

Simplified estimation of the train resistance parameters: full scale experimental tests and analysis

A CEN standard (EN 14067-4, 2005) describes the methodologies for the assessment of the running resistance of railway vehicles starting from full-scale test measurements. According to this standard, the speed dependent terms of the equation of Davis [1] have to be determined by means of coasting tests. In this paper, a new method to estimate the running resistance coefficients from a full-scale coasting test is proposed and compared with the two methods proposed in the CEN standard (the regression method and the speed history identification method). The main advantage of this new method is that it does not require the railway line characteristics to be known and it will be shown that the new method is able to evaluate the coefficients with an accuracy equivalent to that of the other methods considered

Controlled Lactonization of o-Coumaric Esters Mediated by Supramolecular Gels

Fragrances are volatile organic compounds widely used in our daily life. Unfortunately, the high volatility required to reach human receptors reduces their persistency in the air. To contrast this effect, several strategies may be used. Among them, we present here the combination of two techniques: the microencapsulation in supramolecular gels and the use of profragrances. We report a study on the controlled lactonization of four esters derived from o-coumaric acid. The ester lactonization spontaneously occurs after exposure to solar light, releasing coumarin and the corresponding alcohol. To determine the rate of fragrance release, we compared the reaction in solution and in a supramolecular gel and we demonstrated that the lactonization reaction always occurs slower in the gel. We also studied the more suitable gel for this aim, by comparing the properties of two supramolecular gels obtained with the gelator Boc-L-DOPA(Bn)(2)-OH in a 1:1 ethanol/water mixture in different gelator concentration (0.2% and 1% w/v). The gel prepared with 1% w/v gelator concentration is stronger and less transparent than the other and was used for the profragrances encapsulation. In any case, we obtained a significative reduction of lactonization reaction in gel, compared with the same reaction in solution

Full scale experimental tests to evaluate the train slipstream in tunnels

The train slipstream, i.e. the air velocity induced by the train, is one of the most important aerodynamic effects connected to railway vehicles because it has a direct impact on the safety of passengers on the platform and track workers along the railway line. In recent years, a lot of studies were performed to understand the development of this phenomenon in open field, and specific EU standards, the EN 14067–4 and the TSI were issued. Instead, only few studies have been carried out to analyse the train slipstream in confined spaces (as tunnels, line sections with acoustic barriers, etc.), even though the first results of these analyses have shown that the confinement of the air causes more severe conditions regarding the speed of the air flow. This work aims at studying, through a fullscale experimental campaign, the effects on the air flow speed caused by the train passage. The effects of different train parameters (i.e. train type and length, etc.) and infrastructure parameters (i.e. geometry variations) were analysed. Lastly, the results of a specific test considering the presence of a stationary train inside the tunnel while another train is passing are described, to simulate scenarios of ordinary railway traffic

Boc-Protection on L-DOPA: an Easy Way to Promote Underwater Adhesion

The ability of mussels to adhere to underwater surfaces has attracted a lot of attention from the scientific community. As proteins containing L-DOPA (3,4-dihydroxyphenyl-l-alanine) are involved in their adhesion, a common strategy to synthesize adhesives is the incorporation of this amino acid into other compounds. Herein, we report a study on four compounds of the family of Bocx-(L-DOPA)n-OMe (x = 1–3; n = 1,2), that we prepared through simple synthetic steps. Three of them showed the capability of underwater adhesion: while they are not adhesive in the dry phase, the adhesiveness is triggered when the dried sample is immersed in water or any aqueous solutions. The introduction of protecting groups stabilizes L-DOPA, preventing the oxidation of the catechol moiety, and enhances the hydrophobicity, helping the removal of water from the surface to bind. These molecules show good adhesiveness, with different properties, so they may be all used as adhesives for different purposes. These outcomes pave the way for new applications for these materials as green and biocompatible adhesives

Ballast flight under high-speed trains: Wind tunnel full-scale experimental tests

The flying ballast phenomenon has become an important problem, in the last years, because of the development of high speed trains and the consequent increase of the speed up to 350. km/h. The problem is very complex since it is related to both railway infrastructure and train characteristics and since it involves mechanical and aerodynamic effects. The results of an experimental study carried out on the Italian high-speed railway and on a 1:1 real stretch of the railways in wind tunnel are presented in the paper. The study was aimed to analyze the effects of the height of the ballast level, the stone shape in the upper layer of the ballast and the compaction of the ballast bed on the problem. To this purpose a specific wind tunnel test rig was designed to reproduce in the wind tunnel a flow with the same average characteristics of the one measured on the real line, especially in the region close to the ballast and sleepers. Finally, starting from the results of these tests, possible countermeasures to ballast lifting on-set are proposed

Aerodynamic loads in open air of high speed trains: Analysis of experimental data

The homologation of high-speed trains is a demanding and expensive procedure. In particular, the evaluation of train slipstream according to the standard TSI, 2008 is divided in two different test programmes: one concerning the workers at the trackside and the other studying the passengers standing on the platform. This paper presents some slipstream measurements performed on three high speed trains and a comparison between them. The objective is to investigate the slipstream on the platform and relate it to the flow measured at the trackside at the same height with respect to the top of the rail. This topic is currently under revision by the commission in charge of the TSI standard. Interesting evidence concerning the improvements of the aerodynamic performance of new-generation trains are highlighted