• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 1995년도 추계 학술대회논문집
• /
• pp.182-187
• /
• 1995

The present paper explains some advancement made by the authors for the compressible flow computation of the Euler equations based on the unstructured grid and vertex- centered finite volume method. Accurate solutions to the unsteady axisymmetric shock wave propagation problems and three-dimensional airplane flows have been obtained by a high-order upwind TVD and FCT schemes. Unstructured grid adaption is made for the unsteady shock wave problems by the dynamic h-refinement/unrefinement procedure and for the three-dimensional steady flows by the Delaunay point-insertion method to generate three-dimensional tetrahedral mesh enrichment. Some physics of the shock wave diffraction phenomena and three-dimensional airplane flow are discussed.

• 한국공작기계학회논문집
• /
• 제13권6호
• /
• pp.48-55
• /
• 2004

Design for quite operation of fluid power system requires the understanding of noise and vibration characteristics of the system. This paper presents a dynamic response of design of hydraulic circuit. Experimental investigations on the attenuation of pressure ripple in automotive power steering hydraulic pipe line is examined. Also, a mathematical model of hydraulic pipe is p개posed to support a design of the hydraulic circuit. and the impedance characteristics of pressure ripple is analyzed. It is experimentally shown that power steering hydraulic pipe attenuates pressure ripple with high frequency.

• 대한기계학회논문집B
• /
• 제22권2호
• /
• pp.153-161
• /
• 1998

This study describes the results of the analysis of measured rotating stall signal in a centrifugal compressor with vaneless diffuser. Unsteady flow and rotating stall in vaneless diffuser were investigated by measuring of unsteady velocity fluctuation using hot-wire anemometer. Experiments were carried out in several impeller rotating speeds, at different radius ratios. Single hot -wire was used to study the characteristics of rotating stall. As a result, the abrupt rotating stall was detected at all measured impeller rotating speeds and the several flow coefficients which are less than 0.16. The number of the stall cell was one at all measured rotational speeds, and the rotating direction was the same as that of the impeller. As the flow rate decreased, the profile of the phase averaged radial velocity component with time changed from a sawtooth to a sine wave.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
• /
• pp.240-244
• /
• 2004

Characteristics of steady and unsteady cavitation in a turbopump inducer were investigated in this paper. To see the effect of tip clearance on the inducer performance, three cases of tip clearance were tested. The helical inducer, which has two blades with inlet tip blade angle of 7.8 degree and tip solidity of 2.7, was tested in the water. In the non-cavitating condition, the inducer head decreased with increase in the tip clearance. Rotating cavitation and cavitation surge were observed through unsteady pressure measurements at the inducer inlet. The cell number and propagation speed of the rotating cavitation were determined through cross-correlation analysis. During the rotating cavitation one cell rotated at the same rotational speed as that of the inducer rotation and the cavitation surge did not rotate. The critical cavitation number increased with increase in the tip clearance at the same flow rate, but the change of critical cavitation number was small at the nominal flow rate.

• 한국가시화정보학회:학술대회논문집
• /
• 한국가시화정보학회 2002년도 추계학술대회 논문집
• /
• pp.113-116
• /
• 2002

The shock wave discharged from an annular duct leads to very complicated flow features, such as Mach stem, spherical waves, and vortex rings. In the current study, the merging phenomenon and propagation characteristics of the shock wave are numerically investigated using a CFD method. The Harten-Yee's total variation diminishing (TVD) scheme is used to the unsteady, axisymmetric, two-dimensional, compressible Euler equations. The Mach number of incident shock wave $M_s$ is varied in the range below 2.0. The computational results are visualized to observe the major features of the annular shock waves discharged from the tube. On the symmetric axis, the peak pressure produced by the shock wave and its location depend upon strongly the radius of the annular tubes. A Mach stem is generated along the symmetric axis of the annular tubes.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 2006년도 제33회 KOSCO SYMPOSIUM 논문집
• /
• pp.9-11
• /
• 2006

Visualization has played an essential role in the development of our understanding of the complex unsteady flows associated with the initiation, propagation, and extinction of detonation waves. These methods and application to various aspects of detonation are illustrated by results obtained in my laboratory, particularly using combinations of the PLIF technique with other methods. Examples shown will include detonation initiation by projectiles, diffraction over ramps and steps, diffraction out of tubes, detonation implosion, and the cellular structure of detonation waves.

• 한국가시화정보학회:학술대회논문집
• /
• 한국가시화정보학회 2005년도 추계학술대회 논문집
• /
• pp.74-79
• /
• 2005

The tribrachial flame in laminar coflow jet has been investigated experimentally with unsteady propagating condition. With adopting various visualization techniques, including OH-PLIF, Rayleigh Scattering technique, it was confirmed that the location of tribrachial point is on the inclined surface of flame and the propagation speed of tribrachial flame was significantly affected by the velocity gradient.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2001년도 추계 학술대회논문집
• /
• pp.1-9
• /
• 2001

In this paper, some numerical methods recently developed for gas-liquid two-phase flows are reviewed. And then, a preconditioning method to solve cavitating flow by the author is introduced. This method employs a finite-difference Runge-Kutta method combined with MUSCL TVD scheme, and a homogeneous equilibrium cavitation model. So that it permits to treat simply the whole gas-liquid two-phase flow field including wave propagation, large density changes and incompressible flow characteristic at low Mach number. Finally, numerical results such as detailed observations of the unsteady cavity flows, a sheet cavitation break-off phenomena and some data related to performance characteristics of hydrofoils are shown.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
• /
• pp.75-76
• /
• 2003

Direct numerical simulation results of aeolian tones generated by a two-dimensional obstacle (circular cylinder, square cylinder, NACA0012 airfoil) in a uniform flow are presented and the generation and propagation mechanisms of the sound are discussed. The unsteady compressible Navier-Stokes equations are solved by a highly-accurate finite difference scheme over the entire region from near to far fields. The direct numerical simulation results are also compared with the results obtained by Curle's acoustic analogy.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2006년도 추계 학술대회논문집
• /
• pp.18-21
• /
• 2006

This paper investigates LES of turbulent combustion flow based on 2-scalar flamelet approach, where a G-equation and a conserved scalar equation simulate a propagation of premixed flame and a diffusion combustion process, respectively. The turbulent SGS modeling on these flamelet combustion approach is also researched. These LES models are applied to an industrial flows in a full scale gasturbine combustor with premixed and non-premixed flames. The numerical results predict the characteristics of experiment temperature profiles. Unsteady features of complex flames in combustor are also visualized.