• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.04a
• /
• pp.140-144
• /
• 1997

Although the cone type venturi flow meter is superior to another differential pressure type flow meter in precision, the venturi is installed at the pipe as an L beam, so that the dynamic load due to drag force and flow-induced force is generated in the flow meter. In this paper we propose a methodology to evaluate this dynamic load directly by using stain-gages attached on the venturi and we discuss about the dynamic characteristics on the basis of flow-induced vibration theory.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.23 no.2
• /
• pp.138-144
• /
• 2014

This study investigates the air resistance due to deflector configurations of commonly used largetrucksat a driving speedof 80 km/h. Of the 6 models that are considered, the drag causedby the pressure on the front part of the trailer is largest for model 1. For model 1, the lift caused by the difference between the velocities of the upper and lower streams isgreatest amongall the models. Model 6 has the least resistance against the flow stream consideringthedrags and lifts of theflow models. Anoptimal design can be obtainedby investigating thesimulation analysis ofvarious deflector configurationsfor the upper part of largetrucks; this optimum deflector configuration will help reduce the air resistanceon large trucks.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
• /
• 2006.05a
• /
• pp.202-205
• /
• 2006

Recently, high vacuum pumps are widely used in the semi-conduction and liquid-crystal display ( LCD ) process. The composite-type high vacuum pumps are widely used in the various processes. In this study, the pumping performance of composite-type molecular pumps has been investigated experimentally. The experimented pumps are a compound molecular pump ( CMP ) and hybrid molecular pump ( HMP ). The CMP consists with helical-type drag pump, at lower part, and with turbomolecular pump ( TMP ), at upper part. The HMP consists with disk-type drag pump, at lower part, and with TMP, at upper part. The experiments are performed in the outlet pressure of $0.2\;{\sim}\;533\;Pa$. We have measured the ultimate pressure, compression ratio, and pumping speed

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.1825-1829
• /
• 2004

A numerical simulation was performed of flow behind a squareback car with a rear spoiler. Influence of the rear spoiler on drag force has been studied. A lattice Boltzmann method was utilized to portray the unsteady aerodynamics of wake flows. The pressure distributions were employed to examine the vortex formation mode against the rear spoiler. It was found that the separation flow at roof end and c-pillar makes three dimensional vortex structures and the rear spoiler increases pressure on the rear glass surface.

• Advances in aircraft and spacecraft science
• /
• v.10 no.5
• /
• pp.457-471
• /
• 2023

The paper evaluates the aerodynamic coefficients on a blunt-nose re-entry capsule with a conical cross-section followed by a cone-flare body. A computer code is developed to solve three-dimensional compressible inviscid equationsfor flow over a Space Recovery Experiment (SRE) configuration at different flare-cone half-angle at Mach 6 and angle of attack up to 5°, at 1° interval. The surface pressure variation is numerically integrated to obtain the aerodynamic forces and pitching moment. The numerical analysis reveals the influence of flare-cone geometry on the flow characteristics and aerodynamic coefficients. The numerical results agree with wind tunnel results. Increase of cone-flare angle from 25° to 35° results in increase of normal force slope, axial forebody drag, base drag and location of centre of pressure by 62.5%, 56.2% and 33.13%, respectively, from the basic configuration ofthe SRE of 25°.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.37 no.1
• /
• pp.9-18
• /
• 2013

Two-phase vapor-liquid flows exist in many shell and tube heat exchangers such as condensers, evaporators, and nuclear steam generators. To understand the fluid dynamic forces acting on a structure subjected to a two-phase flow, it is essential to obtain detailed information about the characteristics of a two-phase flow. The characteristics of a two-phase flow and the flow parameters were introduced, and then, an experiment was performed to evaluate the pressure loss in the tube bundles and the fluid-dynamic force acting on the cylinder owing to the pressure distribution. A two-phase flow was pre-mixed at the entrance of the test section, and the experiments were undertaken using a normal triangular array of cylinders subjected to a two-phase cross-flow. The pressure loss along the flow direction in the tube bundles was measured to calculate the two-phase friction multiplier, and the multiplier was compared with the analytical value. Furthermore, the circular distributions of the pressure on the cylinders were measured. Based on the distribution and the fundamental theory of two-phase flow, the effects of the void fraction and mass flux per unit area on the pressure coefficient and the drag coefficient were evaluated. The drag coefficient was calculated by integrating the measured pressure on the tube by a numerical method. It was found that for low mass fluxes, the measured two-phase friction multipliers agree well with the analytical results, and good agreement for the effect of the void fraction on the drag coefficients, as calculated by the measured pressure distributions, is shown qualitatively, as compared to the existing experimental results.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.30 no.3
• /
• pp.17-26
• /
• 2002

The pressure distributions on a semi-span wing 1/12 scale mode and sic component aerodynamic forces and moments on a complete 1/16 scale advanced trainer model were measured. To reduce wing-tip vortex strength, 3 wing-tip jet slot shaped(forward $35{^{\circ}C}$ direction, straigt direction, backward $35{^{\circ}C}$ direction) and 3 blowing coefficents (0.004, 0.009, 0.017) were considered. From experiment results, the case of straight direction and blowing coefficent of 0.017 was the best effective in the reduction of drag and in increase of lift-drag ratio and A rate of drag decrease and a rate of lift-drag ratio increase were of most effective on angle of attack 8 degree.

• Proceedings of the KSME Conference
• /
• 2004.11a
• /
• pp.1413-1417
• /
• 2004

The environmental elements which naturally occur can result in structural damages and operating faults of vessels under the navigation and mooring. These primary factors are considered as wind, waves and tide. In order to investigate wind shielding effects with respect to wind load conditions between two ships which face the wind directly or slantingly to the wind direction, this numerical simulation was preferred in terms of the variation of wind loads according to different distances, wind velocities and wind directions between two ships. The results were proved to be quite reasonable, comparing with experimental data from Danish Maritime Institute, and the report, "Environmental Conditions And Environmental Loads" published by Det Norske Veritas.

• Journal of computational fluids engineering
• /
• v.10 no.4 s.31
• /
• pp.39-50
• /
• 2005

An application of the KFLOW3D code which has been developed at KAIST is presented. This paper briefly describes the underlying methodology and summarizes the results for the DLR-F6 transport configuration recently presented in the second AIAA CFD Drag Prediction Workshop held in Orlando, FL, June 2003. KFLOW3D is a parallelized Reynolds averaged Navier-Stokes solver for multi-block structured grids. For the present computations, 2-equation k-$\omega$ WD+ nonlinear eddy viscosity model is used. The emphasis of the paper is placed on the implementation of the k-$\omega$ WD+ model in the multigrid framework and practicality of KFLOW3D for accurately predicting not only the integrated aerodynamic property such as the drag coefficient but pressure distributions.

• Journal of the korean Society of Automotive Engineers
• /
• v.14 no.5
• /
• pp.128-135
• /
• 1992

Using a commercial flow-analysis code VSAERO, a method to predict the drag of an automobile induced by the intake air of the cooling system has been devised. Given the pressure loss coefficient across the radiator, which varies with the radiator shape and the local Re, a simplified model of the internal flow is coupled with VSAERO to find the mass-flow rate through the car. The flow rate is obtained iteratively and that, in turn, gives the drag associated with this flow, which essentially is the momentum carried by the drained air. The results of a few sample cases are presented for two front-end shapes in combination with varying radiator frontal area.