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The pressure variations induced by a CRH380A EMU on a 2.15 m high bridge noise barrier are investigated in a field measurement. The familiar fluctuating pressure time history curves and the peak-to-peak pressure ( ΔP ) distributions attributing to the train head on the barrier surfaces are presented. A comparison of the positive head pulse pressure is made between the measurement results and the data calculated by empirical equations in EN 14067-4. Furthermore, the influences of train speed, train running lines, locations of measurement points, train marshalling length and environmental wind speed on ΔP are analysed. The results indicate as the train speed increases, the corresponding time intervals of ΔP decrease gradually, whereas their slopes become increasingly steep. For a CRH380A EMU, the aerodynamic length of the train head is between 7.63 and 7.64 m, which differs from the physical length of a realistic train with 12.00 m. Along the noise barrier from bottom to top, the ΔP values on the inner surface decrease with the increase of height, while these values on the outer surface increase. Taking the wind direction into account, the ΔP values are a little higher when the high-speed trains run against the wind direction. [ABSTRACT FROM AUTHOR]

Transient aerodynamic pressures induced by the passage of high-speed trains past noise barriers can result in noise barrier damage. This issue is investigated experimentally in the present study by applying pressure sensors to measure the transient aerodynamic pressures acting on the inner surface (close to the railway track) of a 2.15-m high straight-type noise barrier arising from the passage of two different full-scale high-speed trains with different streamlined head cars operating at a speed of 380–420 ​km/h. The results demonstrate that the amplitudes of transient aerodynamic pressures acting on the inner surface of the noise barrier are greatest at the bottom of the noise barrier, and the pressure decreases with increasing height along the barrier. In addition, the dynamic characteristics of the aerodynamic loads are investigated using the fast Fourier transform algorithm. The main frequencies of the transient aerodynamic pressures observed over the train speed range considered are found to be proportional to the train speed and inversely proportional to the single-car length. Moreover, the results of analysis indicate that noise barrier damage can be minimized over the train speed range considered by building noise barriers with natural frequencies residing outside of the 4.21–4.74 ​Hz range. • Full-scale experiment about transient pressure on noise barrier induced by high-speed trains running at 380–420 km/h. • The amplitudes characteristics of transient aerodynamic pressures acting on the surface of the noise barrier. • The main frequencies of the transient aerodynamic pressures at different train speed. [ABSTRACT FROM AUTHOR]

With the increasing need for passenger transportation, the double-unit formation of high-speed trains (HSTs) has been widely employed. However, the dynamic characteristics of the flow around double-unit HSTs have rarely been studied. In this study, the Improved Delayed Detached Eddy Simulation (IDDES) method is employed to analyse the differences in flow fields around single- and double-unit trains. The numerical case is validated through wind tunnel experiments, mesh independence tests and IDDES assessments. The results show that the existence of the double region concentrates the Strouhal number of the aerodynamic force of the wake at 0.15. For the flow downstream of the double region, the slipstream velocity detected until the far-wake region is higher than that in the single-unit case. The standard deviation of the velocity, which reflects the intensity of the turbulence, is also higher for the double-unit case. For the near wake, the vortex dominate region is dominated by flow structure shedding from the snow plough thus similar for two cases; for the downwash dominate region, the double-unit wake exhibits more turbulent flow structures and lower dominant frequency for velocity. The proper orthogonal decomposition results also indicate more turbulent wakes within the downwash dominate region in the double-unit case. [ABSTRACT FROM AUTHOR]

The current research attempts to describe the association between the aerodynamic drag and flow structures induced by train running in time-averaged and time-dependant views. A ICE2 train model is used as the research object, with the flow field solved by Large Eddy Simulation (LES). The validation is carried out through comparison with existing research data, and grid independence study in terms of time-averaged and second-order statistics. Numerical results are firstly presented by description of the time-averaged near wake flow topology based on surface flow visualization. Then, the wake integration method is used both time-averaged and instantaneously to link the aerodynamic force with integrated flow quantities on different wake planes: from the time-averaged perspective, the contribution of different flow terms to total drag is presented and compared; from the instantaneous perspective, the overall wake variation tendency is linked to the fluctuating component of aerodynamic force, based on the wake convection velocity and downstream distance of wake planes. The dynamic features of flow quantities in different locations are presented, with cross-correlation method used to describe the correlation between fluctuating aerodynamic drag and wake motion. Approaches and findings presented in the current study could serve as fundamentals which support future study. • Large eddy simulation employed to solve flow field around a generic ICE2 high-speed train model. • Surface flow visualization techniques utilized to illustrate the time-averaged near wake flow topology. • Wake integration method applied to link the aerodynamic force with integrated flow quantities on different wake planes. • Dynamic features of flow quantities presented, with cross-correlation method used to describe correlation between aerodynamic drag and wake motion. [ABSTRACT FROM AUTHOR]

The aerodynamic loads on the overhead bridge bottom surface induced by train passage are reported in this paper. Both moving model test and numerical simulation approaches at the 1:20 scale are used. The numerical work is validated through both mesh independence tests and comparison with experimental data. Typical pressure variation curves are plotted and compared with previous studies. The peak pressure values' dependence on the Reynolds number is considered through four sets of experiments with different train running speeds. The peak pressure coefficient distribution law for the bridge bottom surface is presented. Differences in the pressure distribution in different bridge bottom areas are explained based on more detailed flow field information. The influence of the bridge height on the aerodynamic load magnitude and time interval is presented. Moreover, the application of the CEN Standard to practical engineering issues is discussed. [ABSTRACT FROM AUTHOR]

Triclosan (TCS) is a kind of chronic toxicity to aquatic organisms. Due to its highly effective antimicrobial, TCS has been widely applied in personal−care products, which naturally poses a potential risk to the ecological system and human health since its release into water−ecological environment. Therefore, it urgently demands a selective, easily separated, recyclable, and low−cost adsorbent to remove the residues of TCS from aquatic environments. In this study, a novel magnetic molecularly imprinted nano−polymers (TMIPs) were prepared for selective adsorption and convenient collection of TCS in aquatic samples, based on a core−shell technique using TCS as template molecule and SiO 2 −coated Fe 3 O 4 nanoparticles as the support substrate. The functional groups, particle size, morphology and magnetic property of TMIPs were characterized by Fourier−transform infrared spectroscopy, scanning electron microscope, transmission electron microscopy and vibrating sample magnetometer, respectively. The obtained TMIPs possessed excellent adsorption capacity (Q e = 53.12 mg g−1), speedy adsorption equilibrium time (2 min) and high selectivity (k' = 6.321) for TCS. Moreover, the pH−tolerance and stability tests manifested that the adsorption capacity of TMIPs for TCS was acid−resistance and could retain 94.2% of the maximum Q e after 5 times removal−regeneration cycles. The feature of magnetically susceptibility can simplify the procedures of sample handling in TCS determination, because the TMIPs of TCS are easy to be recycled from aquatic samples. As an application demonstration, the toxicity test in microalgae confirmed that a tiny amount of TMIPs could significantly eliminate the toxic effect of TCS on Chlamydomonas reinhardtii via the efficient binding with TCS. Image 1 • A kind of nano-polymers with magnetic property and excellent adsorption were prepared by core-shell technique. • The molecularly imprinted nano-materials (TMIPs) have specific binding with triclosan. • High recoveries in spiked aquatic samples proved that the TMIPs were feasible sample handling nanomaterials for rapid enrichment of triclosan. • TMIPs as magnetically recyclable sorbents were successfully applied in the efficient removal of triclosan from aquatic environments. [ABSTRACT FROM AUTHOR]