• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.2
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• pp.190-196
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• 2014

Exhaust system by reinforcement of environment regulation came to the foe study necessity. And Exhaust system has necessary to increase the engine performance and silence. From this cause, Automobile has significantly considered production expense. this study makes process for checking the characteristics about Exhaust variable valve within muffler. Variable valve might reduce the baffle within muffler, It was possible to remove the front muffler. Therefor, To miniaturize a size of muffler might be increased by performance through cost-cutting effect and controling of back pressure. Because the Study on Variable valve installed within muffler, to measure the real data was hardly resulted one of the assignments. From manufactured conduct device, might measure data one of piece which was up-graded of problem. Considering to these point, stressed pressure distribution has analyzed on cross section, floating characteristics about velocity distribution around variable valve using analysis as computational fluid dynamics of Ansys with completed measurement data.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.10
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• pp.1311-1317
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• 2001

To investigate only the effects of the stratified mixture distribution on initial flame propagation and combustion characteristics, the instantaneous equivalence ratio in the spark plug gap and combustion pressure were measured simultaneously In a constant volume chamber, To induce the stratified propane-air mixture distribution near the spark plug, counter-flow typed mixture injection system was used under the constant mean equivalence ratio $\Phi$$\_$mean/= 1.0 The instantaneous equivalence ratio was measured by a single-shot Raman scattering with narrow-band KrF excimer laser. The measuring error was within the limit of $\pm$ 3.5% provided that the proposed method was applied to the measured Raman signals. Judging from mass fraction burned derived from the measured pressure, the optimum combustion characteristics were shown under the condition that the local equivalence ratio in the spark plug was near 1.28$\pm$0.04, and these characteristics were more remarkable at the initial stage of combustion.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.4
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• pp.118-129
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• 1996

In this study, three dimensional flow analysis in a HVAC duct was performed computationally using various turbulence models and compared numerical predictions such as outlet flow split, surface pressure distribution along the duct to experimental data. It's well known that accuracy of computational predictions of flow heavily dependent on turbulent models and discritization method. Therefore, in this work, to assess the ability of turbulent models to predict characteristics of duct flow, three kinds of models, namely standard $k-\varepsilon$, RNG $k-\varepsilon$ and modified $k-\varepsilon$, containing parameter for the effect of streamline curvature were employed and validated one another by comparing with experimental data. In results, modified $k-\varepsilon$ turbulence model allows a successful prediction of static pressure distribution particulary at around strong curvature but little improvement flow split. In the futrue, adoption of CFD to design HVAC duct with modified $k-\varepsilon$ model will bring benefits of producing more accurate prediction, and also give designers more detail information much more than now.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.2
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• pp.66-75
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• 1993

Hydraulic experiments were performed in order to gain an insight into the quantitative differences between the perforated wall caisson and its solid wall counterpart in the local pressure distribution and caisson stability. The results showed that the wave forces acting on local walls were smaller in the perforated wall caisson than in the solid wall caisson. For the caisson stability, the critical weights of the perforated wall caisson also turned out to be smaller than those of the solid wall caisson. The Phenomenon was attributed to the dual effects inherent to the perforated wall caisson, which are the decrease of total horizontal force and the phase difference between the total horizontal and vertical forces.

• The KSFM Journal of Fluid Machinery
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• v.5 no.2 s.15
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• pp.15-21
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• 2002

The hydraulic performance analysis of an entire pump system composed of inducer, impeller, volute and seal for the application of turbopumps is numerically performed using three-dimensional Navier-Stokes equations. A quasi-steady mixing-plane method is used on the impeller/volute interface to simulate the unsteady interaction phenomena. From this work, the effects of each component on the pump performance are investigated at design and off-design conditions through the analysis of flow structures and loss mechanisms. The computational results are in a good agreement with experimental ones in terms of the headrise and efficiency even though very complex flow structures are present. It is found that the asymmetric pressure distribution along the volute wall constitutes the main reason of the difference between experimental and computational results, due to the limitation of the quasi-steady method. Since the volute was found to be over-designed by the pressure distribution of the volute wall, re-design of the volute has been performed, resulting in an improved performance characteristic.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.6
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• pp.38-45
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• 2016

A study was conducted on the effect of leading edge location for the performance characteristics of a centrifugal compressor impeller. Five impellers with different leading edge location were selected for numerical analysis. The impeller with leading edge located 10% away from the inlet about meridional distance from entrance to exit showed the best total pressure ratio and efficiency. Also, this case showed relatively uniform flow distribution because of a weak intensity of the separation region at impeller exit. The impeller with leading edge located far from this location showed lowest total pressure ratio and efficiency. Performance of compressor also decreased due to non-uniform flow distribution at impeller exit.

• Wind and Structures
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• v.20 no.5
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• pp.661-682
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• 2015

This study investigates the use of time-frequency coherence analysis for detecting and evaluating coherent "structures" of surface pressures and wind turbulence components, simultaneously on the time-frequency plane. The continuous wavelet transform-based coherence is employed in this time-frequency examination since it enables multi-resolution analysis of non-stationary signals. The wavelet coherence quantity is used to identify highly coherent "events" and the "coherent structure" of both wind turbulence components and surface pressures on rectangular prisms, which are measured experimentally. The study also examines, by proposing a "modified" complex Morlet wavelet function, the influence of the time-frequency resolution and wavelet parameters (i.e., central frequency and bandwidth) on the wavelet coherence of the surface pressures. It is found that the time-frequency resolution may significantly affect the accuracy of the time-frequency coherence; the selection of the central frequency in the modified complex Morlet wavelet is the key parameter for the time-frequency resolution analysis. Furthermore, the concepts of time-averaged wavelet coherence and wavelet coherence ridge are used to better investigate the time-frequency coherence, the coherently dominant events and the time-varying coherence distribution. Experimental data derived from physical measurements of turbulent flow and surface pressures on rectangular prisms with slenderness ratios B/D=1:1 and B/D=5:1, are analyzed.

• Wind and Structures
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• v.15 no.2
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• pp.87-109
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• 2012

A substantial part of South Africa is subject to more than one strong wind source. The effect of that on extreme winds is that higher quantiles are usually estimated with a mixed strong wind climate estimation method, compared to the traditional Gumbel approach based on a single population. The differences in the estimated quantiles between the two methods depend on the values of the Gumbel distribution parameters for the different strong wind mechanisms involved. Cluster analysis of the distribution parameters provides a characterization of the effect of the relative differences in their values, and therefore the dominance of the different strong wind mechanisms. For gusts, cold fronts tend to dominate over the coastal and high-lying areas, while other mechanisms, especially thunderstorms, are dominant over the lower-lying areas in the interior. For the hourly mean wind speeds cold fronts are dominant in the south-west, south and east of the country. On the West Coast the ridging of the Atlantic Ocean high-pressure system dominate in the south, while the presence of a deep trough or coastal low pressure system is the main strong wind mechanism in the north. In the central interior cold fronts tend to share their influence almost equally with other synoptic-scale mechanisms.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.6
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• pp.80-87
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• 2003

Tank structures in ships are in contact with various fluid. The vibration characteristics of those structures are strongly affected by the added mass due to containing fluid. It is important to predict vibration characteristics of tank structures, but it is difficult to do. That's because the interaction problem concerned with the free surface, the variation of water depth and stiffener is to be considered between the fluid and the structure. Many authors have studied vibration of rectangular tank structures containing water. Kito studied added mass effect of water in contact with thin elastic flat plates. Kim et al. studied flexural vibration of stiffened plates in contact with water. However, few researches on dynamic interaction tank walls with water are reported in the vibration of rectangular tanks recently. in the present report, the coupling effect of added mass of fluid and structural constraint between panels on each vibration mode changing breadth of elastic plate, and dynamic pressure distribution have investigated numerically and discussed.

• Journal of Sasang Constitutional Medicine
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• v.10 no.1
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• pp.295-309
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• 1998

The purpose of this paper was to investigated to the relationship between longevity and Sasang Constitution. The investigation of this paper is composed of 4 parts. First part is investigated to the distribution of sex constitution and constitutional form. Second part is the distribution of the special of body quality(blood pressure, Pulse, Respiration, heredity, stool frequency) and the disease. Third part is the relation of the longevity reason(diet, alcohol intake, smoking). Fourth part is the relationship between the QSCC II and longevity reason. The results were as follows : 1. In case of a macrobian, Soyangin is much more in constitution. 2. A macrobian is generally short and thin. 3. About the macrobian's strength of heredity, there is no any meaningful conclusion, but more studying relationship between heredity and longevity is needed. 4. A macrobian has normal condition in blood pressure, pulse and feces condition. 5. In case of macrobian, the portion of a light eater, non-smoker, and abstainer is high, they like warm food. 6. A macrobian who is active and diligent has high accomplishment and good sociality. Considering above conclusion, a macrobian is related to Soyangin in characteristic of constitution. In the future, more studying is needed whether the macrobian has kept their lives with their unique preservation of health or not.