• Journal of the Society of Naval Architects of Korea
• /
• v.33 no.1
• /
• pp.9-18
• /
• 1996

This paper describes a potential-based panel method for the prediction of unsteady performance of a marine propeller operating in a non-uniform flow field. Boundary-value problem, formulated by distributing the normal dipoles and sources on the blade, the hub and the shed wake, is descretized and numerically analyzed in a discretized time domain. Through an extensive test and comparison with the analytic solution, the convergence in time step is verified for a two-dimensional foil. Unsteaty analysis is then carried out for the DTRC 4118 propeller operating in a harmonic wake, and compared favorably with the experimental result. The present method is shown applicable to the analysis of unsteady performance of the propellers.

• 한국전산유체공학회:학술대회논문집
• /
• 2004.03a
• /
• pp.172-177
• /
• 2004

In the present work, we have interests on the modification of parallel implemented with MPI(Message Passing Interface) programming method, 3-Dimensional, unsteady, incompressible Navier-Stokes equation solver to analyze the low-Reynolds number flow In order to accurate calculation aerodynamic coefficients in low-Reynolds number flow field, we modified the two-equation turbulence model. This paper describes the development and validation of a new two-equation model for the prediction of flow transition. It is based on Mentor's low Reynolds $\kappa-\omega$ model with modifications to include Total Stresses Limitation (TSL) and Separation Transition Trigger (STT)

• Wind and Structures
• /
• v.18 no.5
• /
• pp.529-548
• /
• 2014

This article presents the unsteady aerodynamic performance of crosswind stability obtained numerically for the ATM train. Results of numerical investigations of airflow past a train under different yawing conditions are summarized. Variations of occurrence flow angle from parallel to normal with respect to the direction of forward train motion resulted in the development of different flow patterns. The numerical simulation addresses the ability to resolve the flow field around the train subjected to relatively large yaw angles with three-dimensional Reynolds-averaged Navier-Stokes equations (RANS). ${\kappa}-{\varepsilon}$ turbulence model solved on a multi-block structured grid using a finite volume method. The massively separated flow for the higher yaw angles on the leeward side of the train justifies the use of RANS, where the results show good agreement with verification results. A method of solution is presented that can predict all aerodynamic coefficients and the wind characteristic curve at variety of angles at different speed.

• Proceedings of the KSME Conference
• /
• 2003.04a
• /
• pp.1961-1965
• /
• 2003

The flow analysis is needed to verify the physical phenomena through interruption processes for improving the capacity and the reliability of gas circuit breakers. Moreover the small current interruption performance of GCBs could be predicted by coupling the flow characteristics with the electric field one. In this paper, the unsteady flow characteristics and the traveling trajectory are depicted with a commercial CFD code, PHOENICS, programmed for moving motion of objects. In order to validate computational results, the measured pressure data in cylinder and in front of arcing contact are compared with the test results of small current interruption.

• 한국전산유체공학회:학술대회논문집
• /
• 2004.10a
• /
• pp.91-94
• /
• 2004

A numerical analysis was made to investigate the intensity diminution of a simple silencer for high pressure blast flow fields. Reynolds-Averaged Wavier-Stokes equations were solved for an axisymmetric computational domain constructed by multi block Chimera grids. A blast flow field without the silencer was also calculated to validate the present numerical method. The evolution of high pressure blast flow fields was observed by depicting calculated contours of pressure and Mach number. It was found that the tested silencer could achieve 76 percent intensity diminution.

• Journal of Power System Engineering
• /
• v.3 no.2
• /
• pp.13-19
• /
• 1999

The purpose of the present experimental study is to apply multi-point simultaneous measurement by PIV(Particle Image Velocimetry) to high-speed flow region within a domestic boiler circulation pump. Two different kinds of flow rate($27{\ell}/min,\;19{\ell}/min$)are selected as experimental condition. A volute casing and Impeller made of transparent Polycarbonate were made for the easy access of the illumination laser via fiber optical line and cylinder lens assembly to the measuring region. A CCD camera is syncronized with AOM to acquire clear original particle images. Optimized cross correlation identification to obtain velocity vectors is implemented by direct calculation of correlation coefficients. The instantaneous and time-mean velocity distribution, velocity profile and kinetic energy are represented quantitatively at the full-scale region for the deeper understanding of the unsteady flow characteristics in a commercial circulation pump.

• 한국전산유체공학회:학술대회논문집
• /
• 1996.05a
• /
• pp.46-51
• /
• 1996

The flow field around a three dimensional minivan-like body has been simulated. This study solves 3-D unsteady incompressible Navier-Stokes equations on a non-orthogonal curvilinear coordinate system using second-order accurate schemes for the time derivatives, and third/second-order scheme for the spatial derivatives. The Marker-and-Cell concept is applied to efficiently solve continuity equation. The fourth -order artificial damping is added to the continuity equation for numerical stability. A H-H type multi-block grid system is generated around a three dimensional minivan-like body. Turbulent flows have been modeled by the Baldwin-Lomax turbulent model. The simulation shows three dimensional vortex-pair just behind body. And the flow separation is also observed the rear of the body. It has concluded that the results of present study properly agree with physical flow phenomena.

• 한국전산유체공학회:학술대회논문집
• /
• 2005.04a
• /
• pp.169-172
• /
• 2005

A numerical analysis was made In investigate the pressure diminution of a silencer with baffles for high pressure blast flow fields. Reynolds-Averaged Navier-Stokes equations were solved for an axisymmetric computational domain constructed by multi block Chimera grids. A blast flow field was calculated for the silencers that are with one and three baffles. The evolution of high pressure blast flow fields was observed by depicting calculated contours of pressure. It was found that the tested silencer could achieve 97.7 percent pressure diminution.

• Solar Energy
• /
• v.20 no.4
• /
• pp.53-60
• /
• 2000

An experimental study was carried out in a cavity with upper channel and square heat surface by visualization equipment with Mach-Zehnder interferometer and laser apparatus. The visualization system consists of 2-dimensional sheet light by Argon-Ion Laser with cylindrical lens and flow picture recording system. Instant simultaneous velocity vectors at whole field were measured by 2-D PIV system(CACTUS'2000). Obtained result showed various flow patterns. Severe unsteady flow fluctuation within the cavity are remarkable and sheared mixing layer phenomena are also found at the region where inlet flow is collided with the counter-clockwise rotating main primary vortex. Photographs of Mach-Zehnder are also compared in terms of constant heat flux.

• 한국전산유체공학회:학술대회논문집
• /
• 2003.08a
• /
• pp.152-157
• /
• 2003

As computer capacity has been progressed continuously, the studies of the flow characteristics have been performing by the numerical methods actively. Recent numerical simulation has a tendency to require the higher-order accuracy in time, as well as in space. This tendency is more true in LES and acoustic noise simulation. In this study, 3-dimensional unsteady Incompressible Navier-Stokes equation was solved by numerical method using the fractional step method with the fourth order compact pade scheme to achieve high accuracy To validate the present code and algorithm, 3D flow-field around a cylinder was simulated. The drag coefficient and lift coefficient were computed and, then, compared with experiment. The present code will be tailored to LES simulation for more accurate turbulent flow analysis.