• Title/Summary/Keyword: high-pressure effects

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Numerical Simulation on the Pressure Wave by a High Speed Train Passing through a Tunnel (고속철도 터널에서 발생하는 풍압에 관한 수치해석)

  • Park, Jun;Kim, Hyo-Geun;Lee, Sang-Pil;Ha, Hee-Sang;Yoon, Sung-Wook
    • Proceedings of the KSR Conference
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    • 2011.10a
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    • pp.1674-1680
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    • 2011
  • As the speed of train increases, the effects of the pressure wave generated by the train are becoming more important. To calculate characteristics of the pressure wave generated by a high-speed train passing through a tunnel, several methods are simulated. The pressure waves give rise to large pressure transients which impose the fluctuating loads on the train. It is highly that the pressure transients should be predicted to design the tunnel size and to improve the comfortableness of passengers. In this study, the pressure transients were numerically simulated for a wide range of train speed and compared with the previous verified paper. The simulation results were agreed with the paper, and the characteristics of pressure wave made clear.

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Computational analysis of compressibility effects on cavity dynamics in high-speed water-entry

  • Chen, Chen;Sun, Tiezhi;Wei, Yingjie;Wang, Cong
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.11 no.1
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    • pp.495-509
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    • 2019
  • The objective of this study is to analyze the compressibility effects of multiphase cavitating flow during the water-entry process. For this purpose, the water-entry of a projectile at transonic speed is investigated computationally. A temperature-adjusted Tait equation is used to describe the compressibility effects in water, and air and vapor are treated as ideal gases. First, the computational methodology is validated by comparing the simulation results with the experimental measurements of drag coefficient and the theoretical results of cavity shape. Second, based on the computational methodology, the hydrodynamic characteristics of flow are investigated. After analyzing the cavitating flow in compressible and incompressible fluids, the characteristics under compressible conditions are focused upon. The results show that the compressibility effects play a significant role in the development of cavitation and the pressure inside the cavity. More specifically, the drag coefficient and cavity size tend to be larger in the compressible case than those in the incompressible case. Furthermore, the influence of entry velocities on the hydrodynamic characteristics is investigated to provide an insight into the compressibility effects on cavitating flow. The results show that the drag coefficient and the impact pressure vary with the entry velocity, and the prediction formulas for drag coefficient and impact pressure are established respectively in the present study.

Thermal radiation and some physical combined effects on an asymmetric peristaltically vertical channel of nanofluid flow

  • Amira S. Awaad;Zakaria M. Gharsseldien
    • Advances in nano research
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    • v.16 no.6
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    • pp.579-591
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    • 2024
  • This study explained the effects of radiation, magnetic field, and nanoparticle shape on the peristaltic flow of an Upper-Convected Maxwell nanofluid through a porous medium in an asymmetric channel for a better understanding of cooling and heating mechanisms in the presence of magnetic fields. These phenomena are modeled mathematically as a system of non-linear differential equations, that are solved under long-wavelength approximation and low Reynolds number conditions using the perturbation method. The results for nanofluid and temperature described the behavior of the pumping characteristics during their interaction with (the vertical position, thermal radiation, the shape of the nanoparticle, and the magnetic field) analytically and explained graphically. Also, the combined effects of thermal radiation parameters and some physical parameters on pressure rise, pressure gradient, velocity, and heat distribution are pointed out. Qualitatively, a reverse velocity appears with combined high radiation and Grashof number or combined high radiation and low volume flow rate. At high radiation, the spherical nanoparticle shape has the greatest effect on heat distribution.

The Influence on the Stack effect that Pressure differential system to smoke control in High-rise buildings (초고층 건축물에서 급기가압제연이 연돌효과에 미치는 영향)

  • Lim, Chae-Hyun;Park, Yong-Hwan
    • Proceedings of the Korea Institute of Fire Science and Engineering Conference
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    • 2008.11a
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    • pp.235-238
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    • 2008
  • High-rise buildings with stack effect caused by the foreclosure, which significantly delayed the spread of a fire in effects of these stack effect driving force said. In this research on the stack effect of the lobby if the pressurization of the stairwell analysis of the pressure distribution of the CONTAMW. Overall, the pressurization of the lobby makes it stairwell amount of pressure(+) to the zone in pressure designed to prevent the spread of smoke control performance and found that, the way a normal state and sub-pressurization in the stairwell with stack effect of the turbulence Such as the formation of the upper flow, but, in the upper atmosphere with pressurization was formed by the underlying trend.

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Large-Scale Experiments on the Wave-Induced Liquefaction of Sandbed (파랑작용에 의한 모래지반의 액상화에 관한 대형 수리모형실험)

  • Kang, Yoon-Koo;Suzuki, Kojiro
    • Journal of Ocean Engineering and Technology
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    • v.21 no.3 s.76
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    • pp.26-32
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    • 2007
  • A series of large-scale experiments were carried out in order to examine wave-induced liquefaction in a loosely packed sandbed, its afterward high densification and liquefaction by oscillatory pore pressure. The experiments were conducted in a Large Hydro-Geo Flume that can nearly solve the problems of scale effects of the sandbed, and the 50% sieve diameter of sand was 0.2 mm. The generation of residual pore pressure and its afterward high densification which had observed by Takahashi et al. (1999) in a wave flume experiment using fine sand with the size of 0.08 mm. As a result, the relative density of the sandbed after high densification was increased up to 79% and liquefaction by oscillatory pore pressure was not observed.

A Study on the Simulation of the Fuel Injection System in a Large Low-speed marine Diesel Engine (박용 대형 저속 디젤기관 연료분사계통의 시뮬레이션에 관한 연구)

  • 이창식
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2000.05a
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    • pp.36-44
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    • 2000
  • In his study the simulation was carried out by simplifing and modeling dividing into fuel injectioin pump high pressure pipe and fuel injection valve in the fuel injection system of a low speed marine diesel engine. A computer simulation model was developed using the method of characteristics to analyze the unsteady flow in the fuel injection system considering cavitation and variation of fuel density and bulk modulus. Comparison was commenced between the calculated data and experimental data of pressure and injection quantity at the high pressure distributor in fuel injection system for the training ship "M/V hanara" the effects of the high pressure pipe length diameter plunger diameter nozzle openning pressure were also investigated by simulating results.g results.

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High-Pressure Droplet Vaporization with Emphasis on the Vapor-Liquid Equilibrium Calculation (플래쉬 상평형 계산에 의한 고압 액적기화의 수치적 연구)

  • Lee, Kang-Won;Chae, Jong-Won;Yoon, Woong-Sup
    • 한국연소학회:학술대회논문집
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    • 2001.06a
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    • pp.106-118
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    • 2001
  • A rigorous study of single droplet vaporization under quiescent high pressure atmosphere is attempted adopting method of flash evaporation calculation for vapor-liquid equilibrium. Results due to flash method shows excellent agreement with measurement. Also shown is the present model fairly capable of depicting transients of droplet vaporization under high pressure environment, such as ambient gas solubility, property variation, and multicomponent transports. Systematic treatment of these effects with emphasis on vapor-liquid phase equilibrium revealed; conventional treatment for subcritical droplet vaporization, such as $d^2$-law, leads to erroneous prediction of droplet history, augmented gas solubility is significant under supercritical pressure, and vaporization rate proportionally increase with pressure.

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A Study on a Simulation of a Fuel Injection System in a Large Low-Speed Marine Diesel Engines (박용 대형 저속 디젤기관 연료분사계통의 시뮬레이션에 관한 연구)

  • 강정석;이창식;조권회;최재성
    • Journal of Advanced Marine Engineering and Technology
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    • v.24 no.6
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    • pp.43-52
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    • 2000
  • In this study, a simulation program was developed, which could simulate a fuel injection system for low-speed marine diesel engine. The fuel injection system was divided into fuel injection pump, high pressure pipe and fuel injection valve. The unsteady flow in the high pressure injection pipe was analyzed by the method of characteristics, considering cavitation and variation of fuel density and bulk modulus. It was confirmed that the simulation results were good agree with experimental results of injection pressure and quantity at the high pressure distributor in fuel injection system for the training ship "M/V Hannara". And the effects of the atomizer hole diameter, maximum needle lift, plunger diameter and nozzle opening pressure were also investigated with simulating results.g results.

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A Study on Coupled Field Analysis of 3-D Gas Turbine Blade (3차원 가스터빈 블레이드의 연성 해석에 관한 연구)

  • Park Keun-Hyung;Min Taeg-Ki;Park Chang-Soo
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.15 no.2
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    • pp.38-43
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    • 2006
  • A turbine blade operates under high temperature, high pressure, and the loads have the characteristics that the amplitudes change. Therefore, it is important to perform a stress analysis considering thermal and pressure loads. The purpose of this study is to investigate the effects of these loads on gas turbine blade through thermal stress analysis. The analysis results shows that pressure in gas fluid flow around blade is high in leading edge part, Gas temperature is connections with pressure of flow around blade. The distribution of stress from blade is appearing as is different at suction side and pressure side.

Fundamental Aspects of Resistance Sintering under Ultrahigh Pressure Consolidation

  • Zhou, Zhangjian;Kim, Ji-Soon;Yum, Young-Jin
    • Journal of Powder Materials
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    • v.19 no.1
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    • pp.19-24
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    • 2012
  • The consolidation results of fine tungsten powders, W-Cu composite and W/Cu FGM by using a novel method combining resistance sintering with ultra high pressure have been reviewed. The densification effects of the consolidation parameters, including pressure, input power and sintering time, have been investigated. The sintering mechanism of this method was quite different from other sintering methods. Particle rearrangement, sliding, distortion and crushing due to the ultra high pressure are the dominant mehanisms at the initial stage, then the dominant sintering mechanisms are transient arc-fused processes controlled by the input power.