• Title/Summary/Keyword: Shock pressure

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EXACT RIEMANN SOLVER FOR THE AIR-WATER TWO-PHASE SHOCK TUBE PROBLEMS (공기-물 이상매질 충격파관 문제에 대한 정확한 Riemann 해법)

  • Yeom, G.S.;Chang, K.S.
    • 한국전산유체공학회:학술대회논문집
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    • 2010.05a
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    • pp.365-367
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    • 2010
  • In this paper, we presented the exact Riemann solver for the air-water two-phase shock tube problems where the strength of the propagated sock wave is moderately weak. The shock tube has a diaphragm in the middle which separates water medium in the left and air medium in the right. By rupturing the diaphragm, various waves such as rarefaction wave, shock wave and contact discontinuity are propagated into water and air. Both fluids are treated as compressible, with the linearized equations of state. We used the isentropic relations for the air and water assuming a weak shock wave. We solved the shock tube problem considering a high pressure in the water and a low pressure in the air. The numerical results cleary showed a left-traveling rarefaction wave in the water, a right-traveling shock wave in the air, and the right-traveling material interface.

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Numerical simulation on starting transients in supersonic exhaust diffuser; evolution of internal shock structures with different initial cell pressures (초음속 디퓨져 시동 과정에 관한 수치 모사; 초기 진공도에 따른 디퓨져 내부 충격파 구조의 발달 과정)

  • Park Byung-Hoon;Lim Ji-Hwan;Yoon Woong-Sup
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2005.11a
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    • pp.46-55
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    • 2005
  • For the sea-level performance test of rocket motor designed to operate in the upper atmosphere, ejectors with no induced secondary flow are generally used, which serves dual purposes of evacuating the test cell and performing as a supersonic exhaust diffuser (SED). The main concern of this research is to simulate starting transients in order to visualize evolution of internal shock structures in SED with different initial cell (vacuum chamber) pressures. RANS code with low Reynolds $k-\varepsilon$ turbulence model was employed for these computations. Numerical results were compared with the pressure measurements previously performed [Proceedings of 2004 Annual Conference, KIMST], and showed good agreements with pressure-time history of measured data. In the case of low vacuum chamber pressure, abrupt impingement of the under-expanded supersonic jet from the nozzle onto the diffuser wall was observed, whereas initial impingement point was located downstream and moved slowly upstream in the case of non-vacuum chamber pressure. In spite of initially dissimilar evolution of shock structures, iso-mach contour revealed that the steady shock structures had little difference except the location of flow separation and normal shock.

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Effect of the Residual Excess Pore Water Pressure on the Slope Stability Subjected to Earthquake Motion (잔류 과잉공극수압이 지진 하중을 받는 사면의 안정에 미치는 영향)

  • Lee, Jun-Dae;Kwon, Young-Cheul;Bae, Woo-Seok
    • Journal of the Korean Society of Safety
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    • v.21 no.2 s.74
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    • pp.107-113
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    • 2006
  • Earthquake motion is one of the most significant influence factors on the slope stability. In this paper, an effective stress analysis with the elasto-plastic model was carried out to investigate the behavior of the slope stability subjected to the successive two strong earthquake motions, fore and main shock. The major influence of fore shock to the slope stability was considered as the existence of the residual excess pore water pressure. The paper presents the influence of the existence of the fore shock to slope stability using the numerical analyses. In conclusion, the excess pore pressure by the fore shock was not dissipated during the 7hrs of consolidation. By this residual excess pore water pressure, the factor of safety at the sliding face showed the minimum values, and the deformations of slope was large when compared with the case that considered the main shock only. Furthermore, the minimum of the factor of safety came out after the end of the earthquake motion.

Transient Shock Waves in Supersonic Internal Flow

  • Suryan, Abhilash;Shin, Choon-Sik;Setoguchi, Toshiaki;Kim, Heuy-Dong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2010.05a
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    • pp.357-361
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    • 2010
  • When high-pressure gas is exhausted through nozzle exit to the atmosphere, expanded supersonic jet is formed with the Mach disk at a specific condition. In two-dimensional supersonic jets, the hysteresis phenomenon of the reflected shock waves is found to occur under quasi-steady flow conditions. Transitional pressure ratio between the regular reflection and Mach reflection in the jet is affected by this phenomenon. In the present study, experiments are carried out on internal flow in a supersonic nozzle to clarify the hysteresis phenomena for the shock waves and to discuss its interdependence on the rate of the change of pressure ratio with time. Flow visualization is carried out separately on the straight and divergent channels downstream of the nozzle throat section. The influence that the hysteresis phenomena have on the location of shock wave in a supersonic nozzle is also investigated experimentally.

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A Study on the Aerodynamic Noise of a Supersonic Exhaust Nozzle of Perforated Tube (다공관형 초음속 배기노즐의 공력소음에 관한 연구)

  • 이동훈
    • Journal of KSNVE
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    • v.9 no.1
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    • pp.113-120
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    • 1999
  • A perforated tube nozzle as an exhaust noise suppressor of a high-speed civil transport(HSCT) is proposed. The experimental results for the near and far field sound. the visualization of jet structures and the static pressure distributions in the jet passing through a perforated tube are presented and discussed in comparison with those for a simple tube. It is shown that the perforated tube has an excellent performance to greatly reduce the shock-associated noise and that also the turbulent mixing noise is reduced in the range of a limited jet pressure ratio. This considerable noise reduction is due to the pressure relief caused by the through-flow through the perforated holes. Such a pressure relief results in the transformation of normal shock waves into weak Mach waves of X -type and increases the thrust force of the perforated tube nozzle.

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Changes in Water and Electrolyte Distribution and Blood Glucose Concentration following Irreversible Hemorrhagic Shock (비가역성 실혈성 쇽에서 본 가토심근, 혈장의 전해질 및 혈당량 변화)

  • Kim, Ki-Whan;Nam, Kee-Yong
    • The Korean Journal of Physiology
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    • v.2 no.1
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    • pp.47-52
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    • 1968
  • Twenty white rabbits anesthetized with nembutal (30 mg/kg) were employed in this experiment. Five of them served as controls; the remaining rabbits as experimental group were subjected to irreversible hemorrhagic shock. Shock was induced by bleeding the animals until mean blood pressure decreased to a level of 50-40 mmHg. This level of pressure was maintained for 3-4 hours, after which the drawn blood was reinfused. The reinfusion of blood caused the elevation of arterial pressure almost the control level for some minutes, after which a gradual and progressive decline of blood pressure became evident. This decline was thought to be the result from irreversible hemorrhagic shock. When mean blood pressure declined to less than 50 mmHg, chest was opened and samples of arterial blood and left ventricular muscle were taken. Left ventricular muscle and blood plasma were analyzed for potassium, sodium, chloride and water content. Blood glucose concentration was determined by Somogyi-Nelson's method. Extracellular and intracellular myocardial water and electrolyte content were calculated on the basis that electrolytes are distributed between plasma water and interstitial water according to Gibbs-Donnan equilibrium. In this calculation extracellular water was substituted for Na space. The findings obtained were as follows: 1. The concentration of blood glucose was 87mg% in the controls and it rose to 222 mg% in shock (P<0.01). 2. Plasma potassium elevated significantly from 3.3 mEq/l in controls to 8.0 mEq/l in shock (P<0.01), while small decreases in sodium (151-146 mEq/l) and chloride (102-96 mEq/l) were observed (P<0.3, P<0.1), 3. The changes of blood water content (83.1-84.3%) and cardiac water content (77.5-78.3 gm/100gm WT) were observed. 4. In control animals myocardial potassium levels which averaged 30.2 mEq/100 gmDT rose significantly to 40.3 mEq/100 gmDT in shock (P<0.01), while moderate decreases in sodium(16.3-14.3 mEq/100 gmDT) were observed in shock. 5. The calculated transmembrane resting potential of left ventricular muscle of control animals averaged 95 mV, while rabbits in shock averaged 77 mV. (P <0.01). The findings of this experiment do not correspond with the conclusions that myocardial depression seems to be the cause of irreversible hemorrhagic shock, because the excitability of heart muscle is elevated. From the point of view that the lowered transmembrane resting potential, the cause of death in terminal stage of irreversible hemorrhagic shock may be ventricular fibrillation. It can't be said, however, that the lowered transmembrane resting potential is responsible for the transition from reversible to irreversible hemorrhagic shock. The marked increase in blood glucose suggested that glycogenolysis in the liver is favorably active in shock.

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A Numerical Simulation on the Process of Diaphragm Opening in Shock Tube Flows

  • Kang, M.S.;Nagdewe, S.;Kim, H.D.
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.05a
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    • pp.275-280
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    • 2008
  • Shock tube flow measurement has been often troubled with a finite opening time of diaphragm, but there is no systematic work to investigate its effect on the shock tube flow. In the present study, both the experimental and computational works have been performed on the shock tube flows at low pressure ratios. The computational analysis has been performed using the two-dimensional, unsteady, compressible Navier-Stokes equations, based upon a TVD MUSCL finite difference scheme. It is known that the present computational results reproduce the experimental data with good accuracy and simulate successfully the process of diaphragm opening as a function of time. The concept of an imaginary center is introduced to specify the non-centered expansion wave due to a finite opening time of diaphragm. The results obtained show that the diaphragm opening time is reduced as the initial pressure ratio of shock tube increases, leading to the effect of a finite opening time of diaphragm to be more remarkable at low pressure ratios.

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An Experimental Study on Micro Shock Tube Flow (Micro Shock Tube 유동에 관한 실험적 연구)

  • Park, Jin-Ouk;Kim, Gyu-Wan;Kim, Heuy-Dong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2012.05a
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    • pp.350-355
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    • 2012
  • Past few years have seen the growing importance of micro shock tubes in various engineering applications. A pharma ballistic technique is one such application which uses micro shock tube to accelerate drug particles and penetrate into skin, thus avoiding the usual injection drug delivery system. But for the efficient design of such instruments requires the detailed knowledge of shock characteristics and flow field inside a micro shock tube. Due to many factors such as boundary layer, low Reynolds number and high Knudsen number shock propagation inside micro shock tubes will be quite different from that of the well established macro shock tubes. In the present study, experimental studies were carried out on a micro shock tube of 3 mm diameter to investigate flow characteristics and shock propagation. Pressure values were measured at different locations inside the driven section. From the experimental values other parameters like shock velocity, shock strength were found and shock wave diagram was constructed.

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A Study on Dynamic Characteristics of Automotive Shock Absorber (자동차용 충격 흡수기의 동특성 연구)

  • 남경탁;황성원;신귀수
    • Journal of the Korean Society of Safety
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    • v.17 no.3
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    • pp.1-6
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    • 2002
  • A dynamic characteristics of shock absorber in the various excitation is investigated experimentally. Work diagrams and characteristic curves are used as a experimental standard. The various excitation conditions temperature and noise are very important factors in associated with the reduction of damping force. It is found that the heat occurrence from shock absorber, the gas shock absorber is much higher than oil shock absorber and increased in high speed. As to the variation of damping force, there are no change when the speed is low but we fixed amount of variation by increasing speed and change of new and old decrease. The sound pressure of the swash noise from cycle of shock absorber, we compared with theory sound pressure by experiment.

Experimental and Computational Studies of the Pulse Wave Impinging upon a Vertical Flat Plate (수직평판에 충돌하는 펄스파에 관한 실험적/수치해석적 연구)

  • 이동훈;김희동;강성황
    • Journal of KSNVE
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    • v.11 no.2
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    • pp.285-291
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    • 2001
  • The impingement of a weak shock wane discharged from the open end of a shock tube upon a flat plate was investigated using shock tube experiments and numerical simulations. Harten-Yee Total Variation Diminishing method was used to solve axisymmetric, unsteady, compressible flow governing equations. Experiments were carried out to validate the present computations. The effects of the flat plate and baffle plate sizes on the impinging flow field over the flat plate were investigated. Shock Mach number was varied in the range from 1.05 to 1.20. The distance between the plate and shock tube was changed to investigate the effect on the peak pressure. From both the results of experiments and computations we obtained a good empirical equation to predict the peak pressure on the flat plate.

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