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Prediction of entry compression waves induced by a high-speed train entering tunnel
Rohit Sankaran Iyer,김동현,김희동 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.11
Tunnel wave produced by an entering high-speed train has always been one of the most prominent problems in the field of aeroacoustics. These waves are formed at the entrance of the tunnel and propagate ahead of the train at the local speed of sound. The formation process of the first of the successive compression wave at the entrance decides the nature and intensity of the subsequent waves. Thus, to visualize and understand the formation process; a numerical study has been conducted using commercial computational fluid dynamics (CFD) solver FLUENT 17.1. The dynamic mesh update techniques have been implemented to update the stationary domains as the train moves inside it. Pressure inside the tunnel is measured at distinct points to study the changes in the intensity of the compression wave. The flow physics has been comprehended using pressure plots and contours.
Effect of air chambers on the compression wave propagating along a high-speed railway tunnel
Rohit Sankaran Iyer,DONG HYEON KIM,김희동 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.2
An array of air chambers embedded on the tunnel track is numerically investigated for different configurations. The air chambers act as an in-tunnel countermeasure to alleviate non-linear steepening of compression waves during propagation process thereby mitigating emission of high amplitude micro-pressure waves (MPWs) from the exit portal. The air chambers are designed to entrap the incoming flow and induce damping behavior so as to reduce wave steepening in tunnels. Initially, qualititative comparisons are made between Helmholtz resonator and damping type air chambers. Thereafter, the quantitative assessment of the compression wave properties are checked in detail. From results, over damped air chamber shows 60 % reduction in peak over pressure for weak compression wave whereas the Helmholtz resonator and critically damped shows 35 % and 22 %, respectively. Similarly, due to the presence of over damped air chamber, 17 % reduction in maximum pressure gradient is noticed while critically damped shows close to 10 % reduction.
Prediction of the Entry Compression Waves Produced by a High-Speed Train Entering Tunnel
Rohit Sankaran Iyer,Dong Hyeon Kim(김동현),Heuy Dong Kim(김희동) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11
High-Speed trains entering tunnel produce a system of complicated wave phenomena. A strong compression wave at the entrance is formed, which then propagates ahead of the train at about speed of sound. This exits at the far end of the tunnel as an impulse wave creating a distinct aural discomfort and also provokes mechanical stresses on train cars triggering uneasiness to passengers inside it. Therefore, a study to understand the formation process of the very first of the compression waves produced at the entrance of the tunnel is of prime importance. To understand this phenomenon, a 3-D compressible, unsteady computational investigation has been conducted. The numerical scheme is validated against a reduced scale experimental study. The pressure being measured at two different locations inside the tunnel is used to study the changes in compression waves. The changes are comprehended using pressure contour plots and velocity vectors.
Rohit Sankaran Iyer,Dong Hyeon Kim(김동현),Tae Ho Kim(김태호),Heuy Dong Kim(김희동) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
Entry compression wave is generated in a high-speed railway tunnel due to the train nose ingression at a very high velocity. Due to piston effect there is a sudden rise in pressure inside the tunnel which leads to the formation of the very first or the initial of the successive waves. Ulteriorly, this upsurges into a multitude of wave phenomena due to the reflection and collision of waves on the tunnel wall, thereby, creating a complex sequence of compression waves. Study undertaken here is about the formation process of entry compression wave as a high-speed train enters. A computational investigation on the effect of train nose and blockage ratio has been conducted using dynamic mesh technique. The train is moved using a CG_Motion UDF and the stationary mesh is updated using remeshing and smoothing techniques. The formation process of the entry compression wave has been studied in detail using multiple pressure monitors set on the tunnel wall and the results are comprehended using the pressure plots and contours obtained post the simulations. The post processed contour and vector images gives us a detailed insight on to the flow physics inside the tunnel with the change in above said parameters.