• 대한기계학회논문집B
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• 제26권9호
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• pp.1267-1275
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• 2002

An experimental study was performed to investigate adiabatic wall temperature and heat transfer coefficient around a module cooled by forced air flow. The flow angle of attack to the module were 0$^{\circ}$and 45$^{\circ}$. In the first method, inlet air flow(1~7m/s) and input power.(3, 5, 7W) were varied after a heated module was placed on an adiabatic floor(320$\times$550$\times$1㎣). An adiabatic wall temperature was determinated to use liquid crystal film. In the second method to determinate heat transfer coefficient, inlet air flow(1~7m/s) and the heat flux of rubber heater(0.031~0.062W/$m^2$) were varied after an adiabatic module was placed on rubber heater covering up an adiabatic floor. Additional information is visualized by an oil-film method of the surface flow on the floor and the module. Plots of $T_{ad}$ and $h_{ad}$ show marked effects of flow development from the module and dispersion of thermal wake near the module. Certain key features of the data set obtained by this investigation may serve as a benchmark for thermal-design codes based on CFD.

• 한국유체기계학회 논문집
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• 제17권5호
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• pp.19-26
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• 2014

The cross flow turbine attracts more and more attention for its relatively wide operating range and simple structure. In this study, a novel type of micro cross flow turbine is developed for application to a step in an irrigational channel. The head of the turbine is only H=4.3m and the turbine inlet channel is open ducted type, which has barely been studied. The efficiency of the turbine with inlet open duct channel is relatively low. Therefore, a guide nozzle on the turbine inlet is attached to improve the performance of the turbine. The guide nozzle shapes are investigated to find the best shape for the turbine. The guide nozzle plays an important role on directing flow at the runner entry, and it also decreases the negative torque loss by reducing the pressure difference in Region 1. There is 12.5% of efficiency improvement by attaching a well shaped guide nozzle on the turbine inlet.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2000년도 춘계학술대회 논문집(Proceeding of the KOSME 2000 Spring Annual Meeting)
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• pp.153-158
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• 2000

Flow visualization and PIV measurements were conducted to investigate the flow characteristics of multi-channel with inclination angle. The water flow seeded with tiny vegetable powder as tracers revealed details of flow field. The PIV measurement to acquire multi-point velocity data simulatneously was carried out at three space of plates for 5, 10, and 15mm with variation of inlet flow rates of $0.25m^3/h$ and <$0.5m^3/h.$ Experiment results show that space of plates acts a significant role in separating process.

• 대한기계학회논문집B
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• 제33권7호
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• pp.541-551
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• 2009

Configuration of the inlet transition square duct (hereinafter referred to as "transition duct") for heat recovery steam generator (hereinafter referred to as "HRSG") in combined cycle power plant is limited by the construction type of HRSG and plant site condition. The main purpose of the present study is to analyze the effect of a variation in turbulent flow pattern by roof slop angle change of transition duct for horizontal HRSG, which is influencing heat flux in heat transfer structure to the finned tube bank. In this study, a computational fluid dynamics(CFD) is applied to predict turbulent flow pattern and comparisons are made to 1/12th scale cold model test data for verification. Re-normalization group theory (RNG) based k-$\epsilon$ turbulent model, which improves the accuracy for rapidly strained flow and swirling flow in comparison with standard k-$\epsilon$ model, is used for the results cited in this study. To reduce the amount of computer resources required for modeling the finned tube bank, a porous media model is used.

• International Journal of Fluid Machinery and Systems
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• 제4권4호
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• pp.360-366
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• 2011

Thin circular-arc blade is often used as a guide vane, a deflecting vane, or a rotating blade of low pressure axial-flow turbomachine because of its easy manufacture. Ordinary design of the blade elements of these machines is done by use of the carpet diagrams for a cascade of circular-arc blades. However, the application of the carpet diagrams is limited to relatively low cambered blade operating under optimum inlet flow conditions. In order to extend the applicable range, additional design data is necessary. Computational fluid dynamics (CFD) is a promising method to get these data. In this paper, two-dimensonal cascade performances of circular-arc blade are widely analyzed with CFD. The results have been compared with the results of experiment and potential theory, and useful information has been obtained. Turning angle and total pressure loss coefficients are satisfactorily predicted for lowly cambered blade. For high camber angle of $67^{\circ}$, the CFD results agree with experiment for the angle of attack less than that for shockless inlet condition.

• Structural Engineering and Mechanics
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• 제63권4호
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• pp.567-574
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• 2017

Sedimentation tanks are essential structures to filter the suspended sediments in the inlet flow which are constructed at the inlet of the basins forked from rivers and irrigation canals. The larger the constructed tank, the better the sedimentation process is conducted. However, the construction and dredging costs increase. In this regard, improving the performance and sedimentation efficiency seem necessary by alternative methods. One of these effective methods is using baffle plates. Most of the studies carried out in this field are on the use of these baffles in the primary and secondary sedimentation tanks. Hence, this study is carrier out with the objective of increasing the retention efficiency in the irrigation sedimentation tanks using baffles. To reach this goal, the experiments were carried out in a flume with length 8 meters, width 0.3 meters, and height 0.5 meters, considering a sedimentation tanks with a length of 3 meters, in three different inlet concentration, three flow rates and three Froude numbers. The baffles were mounted at the bottom of the tank and the effects of the angle, height and position in the tanks were investigated. The results showed that on average, employing the baffles increased the sedimentation efficiency 5 to 6% and the highest value was obtained for angle 60 with respect to the flow direction. According to the results of this study, the most favorable height and position of these baffles were obtained to be in 40% of the depth of the flow and 50% of the length of the sedimentation tank, respectively. Also, by increasing the number of baffles, the sedimentation efficiency decreased. Regarding the sedimentation regions in this case, more than 80% of the settled sediments were observed in the middle of the tank measured from the inlet.

• 한국전산유체공학회지
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• 제13권3호
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• pp.44-50
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• 2008

The present study is carried out in order to investigate the effect of the periodic acceleration in the stenosed and bifurcated blood vessels. The blood flow and wall shear stress are changed under body movement or acceleration variation. Numerical studies are performed for various periodic acceleration phase angles, bifurcation angles and section area ratios of inlet and outlet. It is found that blood flow and wall shear stress are changed about ${\pm}20%$ and ${\pm}24%$ as acceleration phase angle variation with the same periodic frequency. also wall shear stress and blood flow rate are decreased as bifurcation angle increased.

• International Journal of Aeronautical and Space Sciences
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• 제3권1호
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• pp.1-8
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• 2002

A numerical analysis was performed on the fluid flow in injector orifice of a liquid rocket engine. The present computational code was verified against the published data for turbulent flow in a pipe with a sudden expansion-contraction. Considered were the parameters for the flow analysis in an injector orifice: Reynolds number, ratio of mass flow rate of the injector orifice and inlet flow rate, and slant angle of the injector orifice. The discharge coefficient increased slightly as the Reynolds number increased. The slant angle of the injector changed critically the discharge coefficient. The discharge coefficient increased by 7% when the slant angle changed from $-30^{\circ}$ to $30^{\circ}$ The ratio of mass flow rate had relatively little impact on the discharge coefficient.

• 대한기계학회논문집B
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• 제28권8호
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• pp.902-909
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• 2004

A steady-state Reynolds averaged Navier-Stokes simulation was conducted to investigate the distribution of the Reynolds stress tensor inside tip leakage vortex of a linear compressor cascade. Two different inlet flow angles ${\beta}=29.3^{\circ}$(design condition) and $36.5^{\circ}$(off-design condition) at a constant tip clearance size of $1\%$ blade span were considered. Classical methods of solid mechanics, applied to view the Reynolds stress tensor in the principal direction system, clearly showed that the high anisotropic feature of turbulent flow field was dominant at the outer part of tip leakage vortex near the suction side of the blade and endwall flow separation region, whereas a nearly isotropic turbulence was found at the center of tip leakage vortex. There was no significant difference in the anisotropy of the Reynolds normal stresses inside tip leakage vortex between the design and off-design condition.

• 한국자동차공학회논문집
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• 제2권1호
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• pp.38-50
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• 1994

To improve the efficiency of internal combustion engines, it is necessary to understand mixed air-fuel in-cylinder flow processes accurately at intake and compression strokes. There is experimental and numerical methods to analyse in-cylinder flow process. In numerical method, standard $k-{\varepsilon}$ model with wall function was mostly adopted in in-cylinder flow process. But this type model was not efficiently predicted in the near wall region. Therefore in the present study, low Reynolds number $k-{\varepsilon}$ model was adopted near the cylinder wall and standard $k-{\varepsilon}$ model in other region. Also QUICK scheme was used for convective difference scheme. This study takes axisymmetric reciprocating model engine motored at 200rpm with a centrally located valve, incorporated 60 degree seat angie, and flat piston surface excluding inlet port. Because in-cylinder flow processes are undergoing unsteady and compressible, averaged cylinder pressure and inlet velocity at arbitrary crank angle are determined from thermodynamic analytic method and incylinder states at that crank angle are iteratively determined from the numerical analytic method.