• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집A
• /
• pp.628-635
• /
• 2001

Hydrodynamic behavior and response of vertical-cylindrical liquid-storage tank is considered. The equation of the liquid motion is shown by Laplace's differential equation with the fluid velocity potential. The solution of the Laplace's differential equation of the liquid motion is expressed with the modified Bessel functions. Only rigid tank is studied. The effective masses and heights for the tank contents are presented for engineering design model.

• 한국자동차공학회논문집
• /
• 제21권2호
• /
• pp.87-97
• /
• 2013

Recently the use of gas spring in the combat and commercial vehicle's suspension is increasing. Because of its nonlinear characteristics, the gas spring can support wide range of dynamic loads and gives good ride quality. In design of gas spring, isothermal and adiabatic processes are applied generally, but those processes could not produce heat transfer effect in the simulation. So in this study, heat transfer differential equation and BWR/Ideal state equation are used to calculate the pressure of gas spring which is changing with time. The numerical analysis showed that the pressure of gas spring forms a hysteresis loop in the both of the state equations. But the peak pressure value of BWR equation over 0.1Hz frequency are higher than that of adiabatic process. And the test results showed that the differences between test results and ideal gas equation are smaller than those of BWR equation, so the ideal equation is more accurate than BWR equation in this case.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집D
• /
• pp.890-895
• /
• 2001

Pressure resonance frequency that is caused in the combustion chamber can be interpreted to acoustic analysis. Until now the pressure resonance has been assumed and calculated to a disc type combustion chamber that neglected the combustion chamber height because the knock occurs near the TDC(top dead center). In this research FEM(fine element method) has been used to calculate the pressure resonance frequency inside the experimental engine combustion. The reduce error of the resonance frequency obtained by FEM has decreased about 50% compared to the calculation of Draper's equation. Due to the asymmetry in the shape of the combustion chamber that was neglected in Draper's equation we could find out that a new resonance frequency could be generated. To make the experimental results equal we could know that the speed of sound that satisfies Draper's equation was selected 13% higher than all the pent-roof type combustion considered.

• 한국터널지하공간학회 논문집
• /
• 제18권3호
• /
• pp.273-282
• /
• 2016

본 연구에서는 기존에 제안된 8가지의 이론식과 3차원 수치해석으로 막장압을 산정하여 비교 검토하였다. 일반적으로 국내 쉴드TBM의 막장압 산정은 이론식과 경험에 따른 방법으로 검토되고 있는 실정이나 복잡한 지층조건, 특수한 지반조건을 통과하는 구간에 대해서는 수치해석을 병행하고 있다. 따라서 이론식으로 산정된 막장압과 수치해석 프로그램에서 산정되는 막장압의 상관관계를 확인하여 막장압의 신뢰성 있는 검토방법을 찾고자 하였다. 막장압 산정시 이론식과 수치해석 모두 사질토와 점성토 지반조건에서 동일하게 검토하였으며, 이론식은 기존에 제안된 식을 사용하였고 수치해석은 쉴드터널의 시공과정을 모사한 3차원 해석을 수행하였다.

• 한국방재학회 논문집
• /
• 제9권5호
• /
• pp.139-145
• /
• 2009

불포화지역의 유기화합물을 제거하기위해 지하수 흐름 해석해를 토양 진공추출 설계에 적용시켰다. 토양 공극 속의 가스 밀도가 압력에 따라 달라지므로 가스나 증기의 흐름을 지배하는 방정식은 비선형이다. 선행 연구자 의해 선형화된 방정식은 지하수 흐름의 지배방정식과 유사하다. 압력대수층과 누수대수층의 압력강하량에 대해서 Massmann의 자료를 이용하여 비교하였다. 압력대수층에 대해서는 Massmann에 의해 제시된 Theis의 해를 수정하였으며 Theis의 해를 검증하기 위해 GASSOLVE9의 프로그램을 이용하였다. Hantush의 해석해를 이용하여 누수대수층 구조에 대해서 압력 강하량을 계산하여 Massmann의 해와 비교하였다. 그 결과 압력강하량에 대해 근사적인 결과를 얻었다.

• 대한기계학회논문집A
• /
• 제27권5호
• /
• pp.779-788
• /
• 2003

This study evaluates the approximation errors of the existing linearized equation for a servovalve nonlinear flowrate characteristic. At first, the errors are evaluated on flowrate/pressure characteristics diagrams. Subsequently, they are investigated with time response simulation results for several hydraulic control systems. To enable systematic evaluation of computational error, the authors propose three kinds of equations with restructured forms of the existing linearized equation. As results of the evaluations, it is ascertained that comparatively good computational accuracy can be achieved with the existing linearized equation when both an operating point for the linearized equation and operating range of the hydraulic system stay near the flowrate axis of the flowrate/pressure characteristics diagram. In addition, the results show that comparatively big computational error may occur when operating range of a hydraulic system stay apart from the flowrate axis of the flowrate/pressure characteristics diagram.

• Korean Journal of Mathematics
• /
• 제14권1호
• /
• pp.113-123
• /
• 2006

The arches may buckle in a symmetrical snap-through mode or in an asymmetry bifurcation mode if the load reaches a certain value. Each bifurcation curve develops as pressure increases. The governing equation is derived according to the bending theory. The balance of forces provides a nonlinear equilibrium equation. Bifurcation theory near trivial solution of the equation is developed, and the buckling pressures are investigated for various spring constants and opening angles.

• 한국가시화정보학회지
• /
• 제12권1호
• /
• pp.13-17
• /
• 2014

The growth of micro bubble has been simulated under the variation of ambient pressure. The Rayleigh-Plesset equation governs the dynamic growth and collapse of a bubble according to pressure and temperature conditions. The Rayleigh-Plesset equation was solved by 4th-order Runge-Kutta method for wide range of pressure variations. As numerical parameters, the pressure difference between initial and final pressures, and the temporal pressure gradient are changed. The results show that the pressure difference has little effect on the growth rate of the micro bubble in the inertia controlled growth region. On the other hand, the growth rate increases linearly with the increase of the pressure gradient.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2010년도 춘계 학술발표회
• /
• pp.1212-1221
• /
• 2010

A theoretical equation was proposed to consider the effect of fill and ponding for the excess pore water pressure in agricultural reservoir on soft clay ground. For the purpose of verification of the proposed equation, laboratory model tests and field tests were performed and excess pore water pressure was compared to those predicted with the Terzaghi's method. The degree of consolidation according to ponding predicted by applying the proposed equation was close to the observed degree of consolidation on the double drainage condition(at DP-3) but it was less than the observed degree of consolidation on the single drainage condition(at DP-5). The predicted excess pore water pressure according to fill and ponding was very applicable to practice because it was close to the observed data.

• 한국생산제조학회지
• /
• 제19권6호
• /
• pp.731-738
• /
• 2010

Cavitation is described by formation and collapse of the bubbles in a liquid when the ambient pressure decreases. Formed bubbles grow and collapse by change of pressure, and when they collapse, shockwave by high pressure is generated. In general, bubble behavior can be described by Rayleigh-Plesset equation under adiabatic or isothermal condition and hence, phase shift by the pressure change in a bubble cannot be considered in the equation. In our study, a numerical model is developed from the mathematical model considering the phase shift from the previous study. In the developed numerical model, size of single spherical bubble is calculated by the change of mass calculated from the change of the ambient pressure in a liquid. The developed numerical model is verified by a case of liquid flow in a narrow channel.