• Journal of Fisheries and Marine Sciences Education
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• v.26 no.4
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• pp.831-837
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• 2014

This paper focuses on the effects of the changes in the resistance characteristics caused by the changes of the POD shape installed in the Hydrofoil vessel, using the CFD(Computational Fluid Dynamics). We input the POD sections' basic shape as the origin of the x and y axis. Then as we cut the x-axis 0 to 2 cm, and the more we cut it, the total resistance value had increased. However, we have recognized the fact that as we cut the POD section, 3 to 5 cm, the resistance value had rather decreased. Furthermore we found out the result that as the cut partition was larger; the POD cross-section would decrease, resulting in the linear decrease of the viscous force.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.5
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• pp.589-596
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• 2006

This study aims to propose a new model axial flow fan which attachs centrifugal blades, and to investigate the effect of centrifugal blades on the performance improvement of new model axial flow fan. A numerical simulation has been conducted using STAR-CD commercial code to solve the three dimensional incompressible Navier-Stokes equation for high Reynolds number $k-{\epsilon}$ turbulent model. Numerical simulation is carried out to investigate the detail phenomenon in the flow field and performance characteristics of new model and normal model fan. Calculation results are compared with normal model's results to investigate which centrifugal blades effect on velocity profile and pressure distribution at various flow field positions. and calculation results show that new model fan can improve the performance of total pressure.

• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.2
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• pp.83-90
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• 2002

An experimental study was conducted to investigate the effects of a leading edge extension(LEX) on the vortex flow field over a delta wing by measuring the total pressure distribution in a subsonic wind tunnel. Freestream velocity was 40m/sec and Reynolds number per meter was $1.76{\times}10^6$. The wing with the LEX experienced a strong interaction between the LEX and wing vortices. As the angle of attack increased, the coupled vortex field of these two vortices maintained its strength and concentricity much better than the vortex field over the wing without the LEX.

• International Journal of Automotive Technology
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• v.6 no.2
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• pp.79-85
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• 2005

This work is to investigate the surface heat flux and combustion characteristics of premixed propane mixture in a constant volume chamber. The experiment of heat flux and combustion characteristics of premixed propane mixture are performed with various equivalence ratio and initial pressure conditions. Based on the experimental results, it is found that the maximum instantaneous temperature is increased with the increase of initial pressure in the chamber. There are significant differences in the burning velocity of premixed propane mixture at different measuring points in the constant volume combustion chamber. A]so, the trends of temperature difference at each measuring points are similar to the burning velocity in the combustion chamber. It is concluded that the total heat loss during the combustion period is affected by the equivalence ratio and the initial condition of fuel-air mixture.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.5
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• pp.107-114
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• 2019

In many military aircraft, s-shaped diffusers are used to prevent the fan blades of the turbofan engine from being exposed to the outside. The inlet configurations of the air intakes for military aircraft vary, such as the rectangular intake of the F-22, the crescent-like intake of the F-16, elliptical intake of the MQ-25. In this study, the aerodynamic performance of s-shaped diffusers with various inlet configurations was evaluated using numerical analysis. In addition, the configuration of the middle section of an s-shape duct was changed to the crescent shape, and the effects on its aerodynamic performance were investigated. As a result, there was a slight difference in total pressure recovery according to various inlet configurations with ellipse-shaped middle sections. Also, the total pressure distortion was the lowest in the rectangular inlet shape. When the configuration of the middle section was changed from an ellipse to a crescent shape, the total pressure recovery remained at a high level, except for the ellipse-shaped inlet configuration. In terms of total pressure distortion, the duct with the crescent-shaped middle section showed a significantly more uniform pressure distribution than that with the ellipse-shaped middle section.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.4
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• pp.499-508
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• 2006

Atmospheric concentrations of polycyclic aromatic hydrocarbons (PAHs) were measured at the Chonbuk National University located in Jeonju, four times between June and November 2002, each time for five days. Twenty-four compounds including five alkyl PAHs and byphenyl were analyzed. Average total concentration of 24 PAHs was 85 $\pm$ 15 ng/$m^3$ and about 94% of PAHs existed in the gas phase. On an average, naphthalene accounted for about 30% of the total PAHs concentration. The gas/particle partitioning was not much varied during the measurement period. High molecular weight PAHs with five and six rings were primarily associated with fine particles less than 1 $\mu$m. Lower molecular weight PAHs were evenly distributed in fine and coarse particles so that their distribution was similar to that of TSP.

• Journal of the Korean Society of School Health
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• v.17 no.1
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• pp.71-83
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• 2004

Purpose: To describe the prevalence, epidemiological characteristics, and related factors of diabetes mellitus in school personnel. Method：5,384 school personnel (2,638 males 2,746 females) received physical examinations at the Seoul School Health Center in 2002. Using the American Diabetes Association criteria, and fasting blood sugar(FBS) was classified as normal at 110>=FBS, borderline 111-125, and the diabetes group 126<=FBS. Related factors of each group were evaluated by gender. Results： In the diabetes group, there were 4.74% males and 0.8% females, and the borderline group was 6.37% males and 2.22% females. The older age group gad a higher distribution in both males and females in the diabetes group. In the diabetes group, the mean and abnormal rate of BMI, systolic hypertension, diastolic hypertension, total cholesterol, GOT, GPT, and GTP were higher than in the normal group. In life style factor, the diabetes group gad a higher distribution of meat eating and smoking more than 20 years than the normal group. The effect of FBS on BMI, BP(blood pressure), total cholesterol, GOT, GPT, and GTP were investigated after controlling for confounding variables. In the borderline and diabetes group, the mean of BMI, BP, total cholesterol, GOT, GPT, and GTP was higher in dose-response effect. In the logistic multiple regression, the related factors of the diabetes group were hypertension and abnormal GTP in males, and abnormal total cholesterol and GTP in females. In the borderline group, the related factors were meat eating, hypertension, and high GOT in males and the older age group, and hypertension, total cholesterol, and abnormal GTP in females. Conclusions: It is possible to manage all related factors of diabetes mellitus except for age. An appropriate program for health promotion is necessary.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.371-374
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• 2006

The objective of this study is to determine the influence of free-stream turbulent intensity on the three-dimensional turbulent flow in a linear turbine cascade. The range of free-stream turbulence intensity considered is 0.7~10%. This study was performed numerically. The results show that the mass averaged loss coefficient increased according to the increase of free-stream turbulence intensity due to increased value of the mass averaged total pressure loss coefficient which was higher than the decreased value of the mass averaged secondary flow loss coefficient. The loss coefficient distribution was changed suddenly at a free-stream turbulence intensity of 10% while the loss coefficient distribution was rarely changed at a lower free-stream turbulence intensity of 5%.

• The KSFM Journal of Fluid Machinery
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• v.13 no.3
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• pp.37-42
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• 2010

This study investigated on details of flow characteristics of a multi-blade fan for domestic ventilation. Experiments and analysis were carried out to describe on flow pattern with variations of cut-off angle near the scroll housing throat, which were performed by PIV measurement for the flow field and by total pressure probes. The stagnation point at cut-off region of the fan moves to the exit of the scroll housing as the cut-off angle increases. The movement of stagnation point and the variation of throat area of the scroll housing influence to the distribution of velocity magnitude at the exit of the fan. Furthermore, a large distortion of the velocity distribution at the scroll exit causes to increase mixing loss along the flow path.

• International Journal of Air-Conditioning and Refrigeration
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• v.8 no.2
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• pp.89-100
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• 2000

Present study explains some experimental results on the aerodynamic noise of the cross-flow fan usually installed in the indoor unit of the room air-conditioners and provides a simple reduction method of radiating sound to decrease the total noise level. The spectra of the noise of the cross-flow fan were analyzed by the spectral decomposition method to characterize the generated sound. The unsteady fluctuating flow field was also measured using the I-type hot-wire probe. Comparing the spectral characteristics of the sound and the flow velocity, a useful noise reduction method was proposed, which bounds the region with a fence where the flow fluctuations were noticeably changed in the same fashion as the source spectral distribution functions vary. To validate the proposed method for reducing noise generated by the cross-flow fan, the sound pressure levels of the cross-flow fan system were compared with and without the bounding fence for various flow rates.