• The KSFM Journal of Fluid Machinery
• /
• v.3 no.2 s.7
• /
• pp.50-56
• /
• 2000

The effects of lobe shapes on the leak flow conductance of Roots-type vacuum pump are studied numerically and experimentally. The modelled lobe shape of Roots-type vacuum pump is two-lobe spur gear. The numerical analyses are performed on leak flows in Roots-type vacuum pump. It is numerically calculated using a 4th-order Runge-Kutta method and is compared with experimental results. Results show that for the case of involute lobe shape the total amount of the leak flow conductance is greater than that of cycloid and Cassini oval lobe shapes.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.23 no.8
• /
• pp.969-977
• /
• 1999

A similarity solution of a steady laminar flow of micropolar fluids past wedges has been studied. The similarity variables found by Falkner and Skan are employed to reduce the streamwise-dependence in the coupled nonlinear boundary layer equations. Numerical solutions of the equations are then obtained using the fourth-order Runge-Kutta method and the distribution of velocity, micro-rotation, shear and couple stress across the boundary layer are obtained. These results are compared with the corresponding flow problems for Newtonian fluid past wedges with various wedge angles. Numerical results show that, keeping ${\beta}$ constant, the skin friction coefficient is lower for a micropolar fluid, as compared to a Newtonian fluid. For the case of constant material parameter K, however, the velocity distribution for a micropolar fluid is higher than that of a Newtonian fluid.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• v.20 no.1
• /
• pp.37-50
• /
• 2016

A large eddy simulation (LES) of a turbulent channel flow is performed by using the third order low-storage Runge-Kutta method in time and second order finite difference formulation in space with staggered grid at a Reynolds number, $Re_{\tau}=590$ based on the channel half width, ${\delta}$ and wall shear velocity, $u_{\tau}$. To reduce the calculation cost of LES, algebraic wall model (AWM) is applied to approximate the near-wall region. The computation is performed in a domain of $2{\pi}{\delta}{\times}2{\delta}{\times}{\pi}{\delta}$ with $32{\times}20{\times}32$ grid points. Standard Smagorinsky model is used for subgrid-scale (SGS) modeling. Essential turbulence statistics of the flow field are computed and compared with Direct Numerical Simulation (DNS) data and LES data using no wall model. Agreements as well as discrepancies are discussed. The flow structures in the computed flow field have also been discussed and compared with LES data using no wall model.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.4 no.5
• /
• pp.215-222
• /
• 1996

This paper reports on theoretical study of the compression process within balanced type vane pump for Electro-Hydraulic Power Steering(EHPS). Equations fo camring profiles are derived, then displacements, velocities, accelerations, and jerks are calculated. Vane side leakages, vane slit leakages, and rotor side leakages are considered and calculated. Numerical integration of flow equation is performed using 4th Runge-Kutta method. As a result of analysis, it is found that chamber pressure depends on rotational speeds, bulk modulus of fluid, notches, camring profiles, and positions of delivery port. Especially, the variation of notch area is the most important factor that prevents pressure from rapid rising.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.3 no.3
• /
• pp.97-108
• /
• 1995

A 3-dimensional double track vehicle model, that has 12-degress-of-freedom, was proposed to analyze handling and riding behaviours of an automotive car. Nonlinear characteristics of the suspension and steering systems of the vehicle model were considered in its equations of motion, which were solved by using the 4th-order Runge-Kutta integration method. Computer simulations for lane change, steady-state handling, and running-over-bump manoeuvres were made and verified by vehicle tests on proving ground. The computed results of the proposed model showed better agreement with test results than those of the conventional 2-dimensional single track model did. Especially they showed good accuracy near the characteristic speed and in high lateral accelerated manoeuvres.

• Journal of Korean Society for Quality Management
• /
• v.20 no.1
• /
• pp.158-167
• /
• 1992

This paper represents the new techniques for optimal sampling plans of reliability applying the mathematical complex number(real and imaginary number) in the complex system of reliability. The research formulation represent a mathematical model Which preserves all essential aspects of the main and auxiliary factors of the research objectives. It is important to formule the problem in good agreement with the objective of the research considering the main and auxilary factors which affect the system performance. This model was repeatedly tested to determine the required statistical chatacteristics which in themselves determine the actual and standard distributions. The evaluation programs and techniques are developed for establishing criteria for sampling plans of reliability effectiveness, and the evaluation of system performance was based on the complex stochastic process(derived by the Runge-Kutta method. by kolmogorv's criterion and the transform of a solution to a Sturon-Liouville equation.) The special structure of this mathematical model is exploited to develop the optimal sampling plans of reliability in the complex system.

• Proceedings of the KIEE Conference
• /
• 1991.07a
• /
• pp.143-146
• /
• 1991

This paper describes the analysis of a capacitor-driven induction coil-gun employing an equivalent circuit. The system differerntial equations are solved by using Runge-Kutta method. The velocity characteristics of projectile and current building in barrel ciols are studied. From the results, it is shown the optimal capacitance of capacitors, charging voltage and initial position of the projectile can be determined. These results will be used as the basis data for the design of capacitor driven coil-guns.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2002.11a
• /
• pp.267-270
• /
• 2002

The fluoescent lamp has been successfully modeled by employing the radial variation of particle density and considering driving circuit effects on the characteristics of discharge process. The electron energy distribution is assumed to have a Maxwellian. The electron mobility and the ambipolar diffusion coefficients are considered to vary with an electron energy rather than a simple uniform value. Energy states of mercury atom in the discharge process are regarded as six levels rather than simple 4 or 5 levels. These discharge processes have been accurately solved by numerically employing mixed the FDM and the 2nd Runge-Kutta method. This model was applied to analyzing real circuit. Simulation and experimental results were presented to verify the feasibility of the modeling. Simulation and experimental results were presented to verify the feasibility of the modeling.

• 한국전산유체공학회:학술대회논문집
• /
• 2005.10a
• /
• pp.151-155
• /
• 2005

Three-dimensional structures of unsteady detonation wave propagating through a square-shaped tube is studied using computational method and parallel processing. Inviscid fluid dynamics equations coupled with variable-${\gamma}$ formulation and simplified one-step Arrhenius chemical reaction model were analysed by a MUSCL-type TVD scheme and four stage Runge-Kutta time integration. Results in three dimension show the two unsteady detonation wave propagating mode, the Rectangular and diagonal mode of detonation wave instabilities. Two different modes of instability showed the same cell length but different cell width and the geometric similarities in smoked-foil record.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.9 no.3
• /
• pp.28-34
• /
• 2010

The suggested coupled system was analyzed using FRF and mode analysis. The eigen-mode of FRF analysis is consistent with that of conventional FFT in spectrum. Also, three numerical responses of second order system, which are coupled, was obtained using the Runge-Kutta Gill method. The displacement, velocity and acceleration response were calculated for the numerical analysis of coupled system and the displacement response was used for the calculation of FRF of this system. Using the mixed response of 1st and 2nd mode in example, the FRF was analysed for the analysis of mixed mode coupled system. Also, its mode shape was acquired by solving the eigen problem of coupled system.