A Computational fluid dynamics study on the relative motion effects for high speed train crosswind assessment

The effect of the relative motion between a train and the surrounding infrastructure may result in critical scenarios where the infrastructure has a significant effect on the atmospheric wind. This paper analyses using a computational dynamics approach the variation of the aerodynamic force coefficients on the leading vehicle of a high speed train due to the relative motion between the train and the infrastructure. A limited increase (below 10 percent) in force coefficients are calculated and a small decrease (below 7 percent) is observed in the characteristic wind curve computation

Indirect model based estimation of cutting force and tool tip vibrational behavior in milling machines by sensor fusion

Real time prediction of cutting tool condition and machined surface finish have been attractive research objectives over the last decades. However, providing practical and reliable solutions is still a demanding task for milling machine tools. One of the most challenging literature goals is to obtain a robust estimation of the cutting forces through indirect sensor measurements since many process and tool related quantities are indirectly linked to cutting forces. Another challenging issue in machining process monitoring and control is prediction of surface finish and quality. As the vibration plays a major role in the surface generation, this can be done by accurate prediction of the vibrational displacements at the tool tip during machining operation. In this paper, a novel model based estimation of cutting force and tool tip acceleration is designed and tested based on data fusion of different sensors measurements. In this context, two sensors (piezoelectric accelerometer and eddy-current displacement both mounted inside the spindle structure) have been utilized to acquire the experimental signals over a wide range of frequencies. In order to predict the above mentioned quantities, an optimal state estimator based on Kalman Filter (KF) is used. The models have been obtained by system identification method based on experimental measurements performed on a machine tool. The model based estimator is fed by real data. The results show that the estimation of the impulse force and tool tip acceleration can be achieved accurately in low and high frequency ranges by assigning different weights to the measurement sensors

Experimental investigation of the effects of embankment scenario on railway vehicle aerodynamic coefficients

The embankment is a typical layout for rail infrastructures, and train aerodynamic coefficients for the analysis of cross-wind effects with this scenario are required by the TSI standard. Nevertheless, wind tunnel tests on scale models with the embankment scenario present problems in the reproduction of the end layout conditions, that is the simulation of a “pseudo-infinite” full scale embankment. In this paper, the effect of different end layouts of the embankment model as well as wall proximity effects are analysed. To study these two effects, two wind tunnel campaigns were carried out on a ETR500 train model 1:45 scaled. In the first tests, performed in a 1.5 x 1 m wide wind tunnel section, different embankment end layouts (wall-to-wall,finite length with and without noses, etc.) were reproduced and tests performed with different Reynolds numbers. The second experimental campaign was then carried out in a wider wind tunnel section (4 x 4 m), with a different distance between the end of the vehicle and the walls of the wind tunnel. From the results of the first experimental campaign it was found that, in the 10°-40° range of wind angle, all the configurations with nose are generally equivalent, in terms of aerodynamic coefficients, to the wall-to-wall one, considered as the reference configuration (error range +/- 10%). Moreover, comparison of the results obtained with the different wind tunnel setups led to the conclusion that the distance from the upstream end of the ground model to the leading edge of the train model is a key parameter for determining aerodynamic coefficients with the embankment scenario, especially around the critical angle where the coefficients reach their maximum values. For this reason, this parameter has to be correctly reproduced to obtain coefficients comparable with full scale values