• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1997.04a
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• pp.235-244
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• 1997

The empirical factor and reaction force based on published data were involved to investigate compressible flows through sudden enlargement and sudden contraction passages. Analytical solutions of engineering interest were obtained from one-dimensional steady compressible gas dynamic equations. The effects of compressibility, cross-sectional area ratio, and inlet Mach number on the air flows were discussed with regards to the total pressure loss and flow choking. The present results provide available information necessary ta design the compressible pipe flow systems.

• The KSFM Journal of Fluid Machinery
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• v.12 no.5
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• pp.33-38
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• 2009

In this study, the effect of flow disturbance such as contraction, expansion pipe and velocity deviation from low velocity of $0.1\;^m/s$ to $2.5\;^m/s$ on the error characteristics of the flowmeter was studied. Flow experiments using flowmeter calibration facility of K-water were undertaken for the cases of ultrasonic flowmeter based on transit-time method and electromagnetic flowmeter. Experimental results are presented that measurement error of expansion pipe are larger than contraction pipe. It is shown that the minimum straight length were required to remain of ${\pm}0.5%$ error for electromagnetic flowmeter and ${\pm}2.0%$ error for ultrasonic flowmeter.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.4
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• pp.468-474
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• 2011

The flow field around baffle located sudden expansion and contraction channel was measured by PIV method and the effect according to height change of baffle built in the flow field was evaluated. The inlet flow velocity and the baffle height influence mutually to the size and flow pattern of the recycle flow of the back of the baffle and the size of the area of the water power jump passing the upper part of the baffle. In case of Reynolds number $Re=4{\times}10^3$, the critical value of baffle height is estimated around h/H=1.6 and there was a decreasing tendency as the inlet flow velocity was increased.

• Journal of computational fluids engineering
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• v.2 no.1
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• pp.8-12
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• 1997

The three-dimensional Euler equations are solved numerically for the analysis of contraction flows in wind or water tunnels. A second-order finite difference method is used for the spatial discretization on the nonstaggered grid system and the 4-stage Runge-Kutta scheme for the numerical integration in time. In order to speed up the convergence, the local time stepping and the implicit residual-averaging schemes are introduced. The pressure field is obtained by solving the pressure-Poisson equation with the Neumann boundary condition. For the evaluation of the present Euler solver, numerical computations are carried out for three contraction geometries, one of which was adopted in the Large Cavitation Channel for the U.S. Navy. The comparison of the computational results with the available experimental data shows good agreement.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.239-240
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• 2008

• Nuclear Engineering and Technology
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• v.53 no.5
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• pp.1416-1428
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• 2021

Pebble flow characteristics can be significantly affected by the configuration of pebble bed, especially for HTGR pebble beds. How to achieve a desired uniform flow pattern without stagnation is the top priority for reactor design. Pebbles flows inside some specially designed pebble bed with arc-shaped contraction configurations at the bottom, including both concave-inward and convex-outward shapes are explored based on discrete element method. Flow characteristics including pebble retention, residence-time frequency density, flow uniformity as well as axial velocity are investigated. The results show that the traditionally designed pebble bed with cone-shape bottom is not the most preferred structure with respect to flow pattern for reactor design. By improving the contraction configuration, the flow performance can be significantly enhanced. The flow in the convex-shape configuration featured by uniformity, consistency and less stagnation, is much more desirable for pebble bed design. In contrast, when the shape is from convex-forward to concave-inward, the flow shows more nonuniformity and stagnation in the corner although the average cross-section axial velocity is the largest due to the dominant middle pebbles.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.573-576
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• 2002

A flow characteristics of automotive oil pump of gerotor type has been investigated numerically. For the simulation of gerotor that have different rotating velocity at inner rotor and outer rotor, node expansion and contraction method was adopted. ASI (Arbitrary Sliding Interfaces) method was also applied at interface between rotating gerotor and stationary volute. The present results showed good agreement with the experimental data.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.4 no.4
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• pp.342-350
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• 1992

An experimental investigation of the stenosis effects on the pressure drop and flow change in the internal flow is presented. Stainless steel tubes of small diameter(3.175mm, 3.4mm) are used for the test section of the flow loop. Percent contraction ranges from 35% to 83% and the stenosis length ratio (L/d) is varied from 2.8 to 8. Water and aqueous glycerol solutions are used for Newtonian fluids and polymer solutions of Separan AP-273 (500 wppm, 1000 wppm) for non-Newtonian fluids. Pressure loss coefficients of non-Newtonian fluids decrease just as those of Newtonian fluids. The loss coefficients of Newtonian and non-Newtonian fluids increase as the percent contraction increases and the loss coefficients of non-Newtonian fluids are larger than those of Newtonian fluids for the same stenosed tube. The loss coefficient increases as the stenosis length ratio increases.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.4
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• pp.22-29
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• 2003

New high-speed depressurized circulating water channel was designed by using the CFD code. Flow in the channel has free surface and pressure in the test section can be depressed. In this study, Flow separation and bubble occurrence were considered in designing the contraction nozzle shape for better flow uniformity Tn the test section. To supplement velocity defect due to the free surface, nozzle injection system more effective in high-speed flow was installed instead of drum system. Necessary power and injection techniques were proposed. And guide vane arrangement was analyzed to reduce the flow resistance and keep quiet free surface from ´surging´. Wave absorber was devised to reduce the wave resistance and to prevent the entrainment of air to the diffuser.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.401-402
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• 2002

The flow characteristics of ice slurry which was made from $6.5{\%}$ ethylene glycol-water solution flowing in the special pipings including the enlargement, the contraction and the orifice were experimentally investigated. The flow patterns and the pressure drops were measured in acrylic pipes when the fraction of ice were varied from $0\;to\;30{\%}$. The pressure drop behavior of the contraction and the orifice appears to be similar to that of the elbow pipe, since these piping may provide similar frictional resistance to the elbow. In the mean while, the pressure drop increased unexpectedly high with the Ice fraction in the enlargement pipe. It seems that the onset of sharp increase in the pressure drop depends on the flowing time as well as the ice fraction and the flow rate.