• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2001년도 유체기계 연구개발 발표회 논문집
• /
• pp.309-314
• /
• 2001

The high efficient steam turbine stage has been analyzed with the help of the 3-dimensional analysis tool. To increase the efficiency of steam turbine stage, the nozzle has to be designed by using the 3-dimensional stacking method. And the bucket has to be designed to cope with the exit flow of nozzle. To verify the stage design, therefore, the numerical analysis of the steam turbine stage was conducted. In this design, CFX-TASCflow was employed to predict the steam flow of the steam turbine stage. The numerical analysis was performed in parallel calculation by using the HP N4000 8 CPUs machine. The result showed the numerical analysis could be used to help to design the steam turbine stage.

• 대한기계학회논문집
• /
• 제19권5호
• /
• pp.1333-1339
• /
• 1995

Recently developed technique of measuring minor species concentration by using the modulation dip in broadband CARS has been applied to the flame structure study of methane/air premixed flames in a counterflow. This method used the modulation dip from the cold band CO Q-branch resonant signal superimposed on the nonresonant background. The measured CO concentration profile in a symmetric and unsymmetric methane/air premixed flames together with the velocity and temperature by using LDV and CARS have been compared with the numerical results adopting detailed chemistry modeling. The results show that there is a satisfactory agreement between the experimental data and numerical results for velocities, temperatures and CO concentrations. And the modulation dip technique of measuring minor species, such as CO is a viable tool for a quantitative measurement in a flame.

• Journal of electromagnetic engineering and science
• /
• 제10권4호
• /
• pp.296-302
• /
• 2010

This paper proposes an approximate equation for broad bandwidth conditions in an antenna feeding probe design with a cylindrical magneto material structure (CMMS). The bandwidth calculation has been conducted according to the relation between the distance ($r_m$) between the magneto material and feeding probe, and the magneto material thickness ($t_m$) for a given ${\mu}_r$. The bandwidth of a proposed antenna with CMM feeding structure is improved about 182 %, when ${\mu}_r=20+j0.001$, in comparison with the bandwidth of an antenna without CMMS. The maximum error extent between the bandwidth calculated by the approximation equation and by the numerical calculation of the proposed antenna is about $\pm$3.2 % for ${\mu}_r=10+j0.001$. The approximation equation proposed in this study can solve the conventional problem of the complex process and the long time required for reiterative calculation, and allow simple and precise design with prediction. The accuracy of an approximated equation is compared with the results calculated by a commercial tool and verified by reasonable agreement between them.

• 한국대기환경학회지
• /
• 제15권6호
• /
• pp.757-765
• /
• 1999

Lagrangian particle dispersion model(LPDM) is an effective tool to calculate the dispersion from a point source since it dose not induce numerical diffusion errors in solving the pollutant dispersion equation. Fictitious particles are released to the atmosphere from the emission source and they are then transported by the mean velocity and diffused by the turbulent eddy motion in the LPDM. The concentration distribution from the dispersed particles in the calculation domain are finally estimated by applying a particle count method or a Gaussian kernel method. The two methods for calculating concentration profiles were compared each other and tested against the analytic solution and the tracer experiment to find the strength and weakness of each method and to choose computationally time saving method for the LPDM. The calculated concentrations from the particle count method was heavily dependent on the number of the particles released at the emission source. It requires lots fo particle emission to reach the converged concentration field. And resulting concentrations were also dependent on the size of numerical grid. The concentration field by the Gaussian kernel method, however, converged with a low particle emission rate at the source and was in good agreement with the analytic solution and the tracer experiment. The results showed that Gaussian kernel method was more effective method to calculate the concentrations in the LPDM.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2002년도 춘계 학술대회논문집
• /
• pp.140-145
• /
• 2002

The purpose of this 3-D numerical simulation is to calculate and examine a 500 kW Horizontal Axis Wind Turbine (HAWT) power performance and compare to calculation data(BEM method) from Delft University. The experimental approach, which has been the main method of investigation, appears to be reaching its limits, the cost increasing relate with the size of wind turbines. Hence, the use of Computational Fluid Dynamics (CFD) techniques and Navier-Stokes Solvers are considered a very serious contender. We has used the CFD software package CFX-TASC flow as a modeling tool to predict the power performance of a wind turbine on the basis of its geometry and operating data. The wind turbine with 40m diameters rotor, it was scaled to compare with the calculation data from delft university. The HAWT, which has eight-rpm variations are investigated respectively. The pitch angle is $+0.5^{\circ}$ and wind speed is fixed at 5m/s. The tip speed ratio (TSR) of the HAWT ranging from 2.89 to 9.63.

• Journal of the Korean Physical Society
• /
• 제73권11호
• /
• pp.1750-1759
• /
• 2018

A complete code-package for gyrotron simulation to analyze its performance is under development in UNIST, Korea. We first time report the present status of the code-package named as UNIST Gyrotron Design Tool (UGDT). It can perform design simulations for gyrotron's interaction cavity, RF window, and the essential mode calculations including the study of mode competition. We will discuss about its salient features, theory, numerical implementation, and its calculation result for 95 GHz UNIST Gyrotron. Moreover, we will validate its capability to perform the mode competition calculation for fundamental and second harmonic modes.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2000년도 유체기계 연구개발 발표회 논문집
• /
• pp.312-317
• /
• 2000

High efficient steam turbine stage has been developed with the help of the 3-dimensional design tool. In this stage design, the compound leaned stacking method has been adopted to reduce the secondary flow loss of a turbine passage and to increase the performance efficiency for the turbine nozzles. And the turbine buckets have been designed with the quasi-3-dimensional turbomachinery blade design method. To verify the stage design, therefore, the 3-dimensional numerical simulation of a steam turbine stage was conducted. In this design, CFX-TASCflow was employed to predict the turbulent flow of a steam turbine stage. The analysis was performed in parallel calculation using the HP N4000 8 CPUs machine. The result showed CFX-TASCflow could be used as the 3-dimensional flow analysis tool of steam turbine design.

• Nuclear Engineering and Technology
• /
• 제36권5호
• /
• pp.375-387
• /
• 2004

This paper presents a transient multicomponent mixture analysis tool developed to analyze the molecular diffusion, natural convection, and chemical reactions related to air ingress phenomena that occur during a primary-pipe rupture of a high temperature gas-cooled reactor (HIGR). The present analysis tool solves the one-dimensional basic equations for continuity, momentum, energy of the gas mixture, and the mass of each gas species. In order to obtain numerically stable and fast computations, the implicit continuous Eulerian scheme is adopted to solve the governing equations in a strongly coupled manner. Two types of benchmark calculations were performed with the data of prerious Japanese inverse U-tube experiments. The analysis program, based on the ICE technique, runs about 36 times faster than the FLUENT6 for the simulation of the two experiments. The calculation results are within a 10% deviation from the experimental data regarding the concentrations of the gas species and the onset times of natural convection.

• 한국공작기계학회논문집
• /
• 제10권2호
• /
• pp.124-129
• /
• 2001

The level surface approach for following flame front propagating in a premixed medium is adapted to incorporate the flameholding scheme. This allows one to follow the flameholding scheme. This allows one to follow the motion of an N-1 dimensional surface in N space dimensions. The flame speed may be an arbitrary function of flame geometry and the front is passively advected by an underlying flow field. This algorithm provides and accurate calculation of the flame curvature which may be needed for the flame propagation computation and thereby the estimation of curvature-dependent flame speeds. A numerical demonstration of this method-ology is applied to simulate the excursion of an anchored V-flame and locate the final equilibrium position.

• 한국CDE학회논문집
• /
• 제8권4호
• /
• pp.278-288
• /
• 2003

Presented in this paper is a numerical method for calculating the intersection points between Z-map vectors and the tool swept surface for circularly moving filleted-end mills. In numerically controlled(NC) machining simulation for large moulds and dies, a workpiece is frequently approximated as a set of z-axis aligned vectors, called Z-map vectors, and then the machining processes can be simulated through updating the Z-map with the intersection points. Circular motions are typically used for machining the free-form surfaces. For fast computation, we express each of intersection points with a single-variable non-linear equation and calculate the candidate interval in which the unique solution exists. Then, we prove the existence of a solution and its uniqueness in this candidate interval. Based on these properties, we can effectively apply numerical methods to finally calculate the solution of the nonlinear equation within a given precision. Experimental results are given for the case of a TV monitor and the hood of a car.