Stepwise approximation of an optimally flared tunnel portal

Winslow, A.; Howe, M. S.

doi:10.1016/j.jsv.2004.01.039

Cited by 5 publications

(3 citation statements)

References 5 publications

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“…The values ᐉ′/ᐉ of the nondimensional end correction given in the final column of Table I were computed from the numerical solutions. Laplace's equation has to be solved once only for each portal, and the procedure is equivalent to a preliminary calculation of a portal Green's function [24,28]. When ∂ϕ*/∂x is known equation (1) can be applied to any train entering the tunnel along any track whose centreline is offset a distance z t from the tunnel axis.…”

Section: The Velocity Potential ϕ*mentioning

confidence: 99%

Influence of a Scarfed Portal on the Compression Wave Generated by a High-Speed Train Entering a Tunnel

Winslow

Howe

Iida

2005

Journal of Low Frequency Noise, Vibration and Active Control

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An optimally designed entrance portal must be capable of minimizing the maximum growth rate of the compression wave generated when a high-speed train enters a tunnel. A theoretical and experimental investigation has been made to determine the changes in compression wave characteristics produced when the portal is ‘scarfed’ with tapering side walls. It is concluded that portal modifications of this type are unlikely to produce a significant reduction in the maximum compression wave growth rate. Small decreases in growth rate are possible (up to about 15%) for scarf walls extending a distance beyond the tunnel entrance of the order of the tunnel height, but little or no additional improvement is achieved with longer walls.

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Section: The Velocity Potential ϕ*mentioning

confidence: 99%

Influence of a Scarfed Portal on the Compression Wave Generated by a High-Speed Train Entering a Tunnel

Winslow

Howe

Iida

2005

Journal of Low Frequency Noise, Vibration and Active Control

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“…By similarly neglecting small 'end corrections' at compared to the contribution to sound generation by the section of the vortex above the mouth in it is also permissible to use a two-dimensional approximation for . This is very convenient, because in two dimensions Laplace's equation can be solved very easily for different positions of the cross-beam using a conventional 'spread sheet' programme on a personal computer [11,12].…”

Section: The Acoustic Pressurementioning

confidence: 99%

Cavity Mode Excitation by Vortex Shedding from a Cross-Beam

Winslow

Howe

2004

International Journal of Aeroacoustics

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An analysis is made of the tonal acoustic radiation produced by nominally steady, low Mach number flow past a shallow, rectangular wall cavity in the presence of a cross-beam in the flow adjacent to the cavity. At 'lock-on' the frequency of vortex shedding from the beam is equal to one of the resonant frequencies of the cavity. The sound produced by this vorticity is augmented by the presence of the cavity and is calculated for the lowest order resonance frequency of the cavity by using a Green's function derived by Howe (International Journal of Aeroacoustics 2, 347-365, 2003). Except for beams of very small cross-section, the efficiency of the aeroacoustic coupling between the beam and the cavity depends on the position of the beam above the cavity. Our results indicate that the coupling is strongest when the beam lies above the cavity mouth between the cavity leading edge and the centre of the mouth. The analysis makes use of two alternative models of vortex shedding, involving either an array of discrete, rectilinear vortices or a continuous, time-harmonic vortex sheet in the wake of the beam. At lock-on each of these models supplies essentially identical predictions of the acoustic sound power radiated directly away from the cavity.

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“…Problems such as micro-pressure wave, wake flow, and piston wind induced by a passing train not only pose threats to safe and stable train operation but also reduce passenger comfort. In many countries, these problems are usually alleviated by optimizing the opening rate of tunnel hoods [2][3][4] and redesigning tunnel portals [5][6][7]. Studies have shown that some new tunnel portals can effectively reduce the pressure gradient.…”

Section: Introductionmentioning

confidence: 99%

Numerical Analysis of the Tunnel-Train-Air Interaction Problem in a Tunnel with a Double-Hat Oblique Hood

Zhang¹,

Zhang²,

Xiao³

2023

Fluid Dynamics &Amp; Materials Processing

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The tunnel-train-air interaction problem is investigated by using a numerical method able to provide relevant information about pressure fluctuations, aerodynamic drag characteristics and the "piston wind" effect. The method relies on a RNG k-ε two-equation turbulence model. It is shown that although reducing the oblique slope can alleviate the pressure gradient resulting from initial compression waves at the tunnel entrance, the pressure fluctuations in the tunnel are barely affected; however, a large reduction of micro-pressure wave amplitudes is found outside the tunnel. In comparison to the case where no tunnel hood is present, the amplitudes of micro-pressure waves at 40 m from the tunnel reach an acceptable range. The aerodynamic drag of the head and tail fluctuates greatly while that of the intermediate region undergoes only limited variations when the high-speed train passes through the double-hat oblique tunnel. It is shown that the effects of the oblique slope of the portal on the aerodynamic drag can almost be ignored while the train speed plays an important role.

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Stepwise approximation of an optimally flared tunnel portal

Cited by 5 publications

References 5 publications

Influence of a Scarfed Portal on the Compression Wave Generated by a High-Speed Train Entering a Tunnel

Influence of a Scarfed Portal on the Compression Wave Generated by a High-Speed Train Entering a Tunnel

Cavity Mode Excitation by Vortex Shedding from a Cross-Beam

Numerical Analysis of the Tunnel-Train-Air Interaction Problem in a Tunnel with a Double-Hat Oblique Hood

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