• The KSFM Journal of Fluid Machinery
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• v.7 no.6 s.27
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• pp.28-37
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• 2004

An experimental study is conducted to investigate flow characteristics on a small axial-type turbine which is applied as the rotating part of air tools. It operates in a partial admission due to consumption restriction of the high pressure air. In this operating condition, it is necessary to understand flow characteristics for obtaining the high specific output power. Tested turbine consists of two stages and the mean radius of flow passage is less than 10mm. A 6 bar pressure air is used to operate the turbine. The experimental results show that flow angles depend on the measuring location along the circumferential direction, but its discrepancy is alleviated along the axial direction. Absolute flow velocities show three times difference according to the measuring location at the exit of the first rotor due to the partial admission, but they show similar value at the exit of the second rotor by the velocity diffusion. From the measured flow angles and velocities, a ratio of output power obtained by the first and second rotor is estimated. It shows that the output power obtained by the second rotor is about $11\%$ to that by the first rotor at 60,000 RPM. It is effective therefore to improve the first rotor for increasing the turbine output power.

• Proceedings of the KOSOMBE Conference
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• v.1995 no.05
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• pp.113-116
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• 1995

Steady and physiological flows of a Newtonian fluid and blood in the bifurcated arterial vessel are numerically simulated. Distributions of velocity, pressure and wall shear stress in the bifurcated arterial vessel are calculated to investigate the differences between steady and physiological flows. For the given Reynolds number physiological flow characteristics of a Newtonian fluid and blood in the bifurcated arterial vessel are quite different from those of steady flows. No flow separation or flow reversal in the bifurcated region in the downstream after stenosis appears during the acceleration phase. Also, no recirculation region is seen for steady flows. However, during the deceleration phase the flow began to exhibit flow reversal, which is eventually extended to the entire wall region.

• International Journal of Fluid Machinery and Systems
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• v.4 no.1
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• pp.209-216
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• 2011

The flow upstream of a centrifugal pump impeller has been investigated by both experimental test and numerical simulation. For experimental study, the flow field at four sections in the pump suction is measured by using PIV method. For calculation, the three dimensional turbulent flow for the full flow passage of the pump is simulated based on RANS equations combined with RNG k-$\varepsilon$ turbulence model. From those results, it is noted that at both design lo ad and quarter load condition, the pre-swirl flow whose direction is the same as the impeller rotation exists at all four sections in suction pipe of the pump, and at each section, the pre-swirl velocity becomes obviously larger at higher rotational speed. It is also indicated that at quarter load condition, the low pressure region at suction surface of the vane is large because of the unfavorable flow upstream of the pump impeller.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.3
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• pp.341-349
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• 1997

The characteristics of defect correction method are discussed in a sample heat conduction problem showing the numerical solution of the error correction equation can predict the error of the numerical solution of the original governing equation. A way of using defect correction method combined with the existing algorithm for the incompressible fluid flow, is proposed and subsequently tested for the driven square cavity problem. The error correction equations for the continuity equation and the momentum equations are considered to estimate the errors of the numerical solutions of the original governing equations. With this new approach, better velocity and pressure fields can be obtained by correcting the original numerical solutions using the estimated errors. These calculated errors also can be used to estimate the orders of magnitude of the errors of the original numerical solutions.

• Journal of the korean Society of Automotive Engineers
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• v.14 no.6
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• pp.99-104
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• 1992

The complex geometry of the engine room of a passenger car has been modelled two-dimensionally and the thermal and fluid flow therein have been analyzed by using a commercially available code, PATRAN/FLORAM$\mid$N. FLOTRAN adopts a finite element method with streamline upwind formulation for convective terms and the k-.epsilon. turbulence model to solve the three dimensional turbulent flow and heat transfer problems. Velocity vectors, pressure and temperature distributions have been obtained for various cases with different arrangements of license plate, underbody-covers and air dams. The results show that the numerical analysis using PATRAN/FLOTRAN can predict qualitatively well the practical phenomena.

• International Journal of Fluid Machinery and Systems
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• v.6 no.3
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• pp.144-151
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• 2013

In this paper, the design method of a low-head propeller-type hydro turbine is studied for various numbers of blades on an axial propeller. We also investigate the relationship between geometrical parameters and internal performance parameters, such as angular velocities (100, 200, 300, 400 rpm) and 2.5~4m low heads through a three-dimensional numerical method with the SST turbulent model. The numerical results showed that the blade number had a more dominant influence than the change in heads and rotational speed on the flow characteristics of the turbine. The distributions of pressure and velocity in the streamwise direction of the propeller turbine were graphically depicted. Especially, the relationship among dimensionless parameters like specific speed ($N_s$), flow coefficient (${\phi}$) and power coefficient (P) were investigated.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.10a
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• pp.304-310
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• 2001

Flow pulsation often causes vibration and noise in piping systems and therefore has been a troublesome concern for fluid system engineers. According to frequency increase in this paper under the influence wave form of velocity in springly flow and viscosity are drop coefficient of viscosity become increase so that impedance and resistance. The transient variations of flow rate are measured by a modified impedance tube method which is realized by virtue of the present analytical technique. At pipe line in order to eliminate vibration, confirm happened intermittently impedance characteristics. We make a test and frequency analysis and have to minimize obstructive component at hydraulic circuit.

• Journal of the Korean Society of Combustion
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• v.8 no.4
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• pp.15-23
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• 2003

The zone conditional two-fluid equations are derived and validated against DNS database of a premixed turbulent flame. The conditional statistics of major flow variables are investigated to understand the mechanism of flame generated turbulence. The flow field in burned zone shows substantially increased turbulent kinetic energy, which is highly anisotropic due to reaction kinematics across thin f1amelets. The transverse component may be larger than the axial component for a distributed pdf of the flamelet orientation angle, while the opposite occurs due to redistribution of turbulent kinetic energy and flamelet orientation normal to the flow at the end of a flame brush. The major source or sink terms of turbulent kinetic energy are the interfacial transfer by the mean reaction rate and the work terms by fluctuating pressure and velocity on a flame surface. Ad hoc modeling of some interfacial terms may be required for further application of the two-fluid model in turbulent combustion simulations.

• International Journal of Air-Conditioning and Refrigeration
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• v.12 no.4
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• pp.198-205
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• 2004

An experimental study was carried on the characteristics of fluid flow and heat transfer in a fluidized bed shell-and-tube type heat exchanger with corrugated tubes. Seven different solid particles having same volume were circulated in the tubes. The effects of vari­ous parameters such as water flow rates, particle geometries and materials, and geometries of corrugated tubes on relative velocities and drag coefficients were investigated. The present work showed that the drag force coefficients of particles in the corrugated tubes were usually lower than those in the smooth tubes, meanwhile the relative velocities between particles and water in the corrugated tubes were little higher than those in the smooth tubes except the particles of glasses.

• Journal of Mechanical Science and Technology
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• v.16 no.5
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• pp.720-731
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• 2002

Flow with moving free surfaces is analyzed with an the Eulerian coordinate system. This study proposes a semi-implicit filling algorithm using VOF in which the PLIC (Piecewise Linear Interface Calculation) -type interface reconstruction method and the donor-acceptor-type front advancing scheme are adopted. Also, a new scheme using extrapolation of the stream function is proposed to find the velocity of the node that newly enters the computational domain. The effect of wall boundary conditions on the flow field and temperature field is examined by numerically solving a two-dimensional casting process.