• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2004년도 추계학술대회 논문집
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• pp.10-13
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• 2004

The PSP(pressure sensitive paint) technique has recently received a large attention as a new revolutionary optical method to measure absolute pressure distribution on a model surface. The PSP technique can be applied to quantitatively investigate flow structure using a CCD camera and image processing technique. In the static calibration, the luminescent intensity of PSP coatings was measured from 0kPa to 11kPa with 0.5, 1, 2kPa increments. In this study, the low-pressure PSP technique was applied to an oblique impinging jet to measure pressure field variations on the impingement plate with varying angle of an oblique jet. The flow structure over the impingement plate was visualized using a surface tracing method. As a result, the detail pressure field distributions of the oblique low-speed impinging jet were visualized effectively using the PSP technique.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1613-1618
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• 2004

Diffuser is an important fluid-mechanical equipment to convert kinetic energy into pressure energy. Many of the experimental and theoretical researches have been done in a diffuser but the understanding of energy transfer and detailed mechanism of energy dissipation is unclear. In this study, computations were performed using a numerical method with SIMPLE algorithm for conical diffuser with various diffuser angles and diffuser lengths. Also, we investigated the pressure recovery coefficient in conical diffuser by inserting strut. In this paper, we showed that the strut can cause a rising pressure recovery.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.473-478
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• 2003

This paper presents static and dynamic measurement of the stress and motion characteristics for crawler type excavators. Eight scenarios were prepared for static measurement based on two extreme digging positions, maximum digging reach position and maximum digging force position. The measured items for static motion included stress, cylinder pressure, cylinder stroke and digging force. The measured static stresses showed that asymmetric digging force acting on a bucket induced higher stress level than symmetric one. The measured static pressures and digging forces also agreed with design pressures and design digging forces, respectively. The dynamic measurement was performed for two types of motion, that is, simple reciprocation of each cylinder and actual digging motion. The measured items for dynamic motion were stroke and pressure of each cylinder, stresses on the working device and acceleration on the upper plate of an arm. The measured data showed that the natural frequency of the excavator highly depended on the hydraulic stiffness of cylinders. Digging motion tests revealed that digging motion was closer to static motion rather than dynamic one.

• 한국지반공학회논문집
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• 제20권1호
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• pp.101-108
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• 2004

최근 30년간 EPS 블록은 전 세계적으로 그 사용량이 증가하고 있으며, 국내$.$외적으로 EPS 블록의 적용 분야가 확장되고 있는 추세에 있다. 그 대표적인 사례로 EPS 블록의 압축성에 따른 아칭효과를 이용한 옹벽, 교대, 매설관등 지반구조물에 작용하는 토압 저감 분야를 들 수 있다. EPS 블록은 경량성에 기인한 우수한 시공성과 밀도 변화에 따른 균질한 공학적 특성을 가지고 있으며, 또한 압축재로서 최적의 재료적 특성을 갖추고 있다. 일반적으로 EPS 블록은 밀도가 낮은 경우 동일한 하중 아래에서 보다 압축성이 우수한 경향을 보이나, 밀도가 10kg/$\textrm{m}^3$ 이하인 경우 발포 비드간 결합력이 약하여 쉽게 파괴되는 성질이 있으므로 지반공학적으로 이용할 때에는 10kg/$\textrm{m}^3$ 이상의 제품을 이용하는 것이 바람직한 것으로 알려져 있다. 본 연구에서는 지반구조물의 하중 저감을 위한 아칭재로서의 EPS 블록의 현장 적용성 평가를 위하여 콘크리트 옹벽과 콘크리트 박스 암거를 대상으로 현장시험시공을 수행하였으며, 현장시험시공 결과 아칭재인 EPS 블록을 사용할 경우 기존의 이론적인 토압에 비하여 콘크리트 옹벽의 경우 약 20% 정도, 콘크리트 박스 암거의 경우 약 45∼53% 정도인 것으로 평가되었다.

• 한국운동역학회지
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• 제24권2호
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• pp.103-109
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• 2014

The study aimed to examine the effect of a corrective exercise on Cobb's angle and static and dynamic foot pressure in patients with kyphosis. Patients with kyphosis participated in a 12 weeks of corrective exercise program. Participants were randomly assigned to a corrective exercise group (n=17) and a control group (n=17), and corrective exercise for 60 minutes are executed every 3 times a week. All data were analyzed by two-way repeated measured ANOVA. Statistical level was set up as a=.05. As a result, Cobb's angle had significantly effects according to time and groups. Anterior and posterior part of static foot pressure showed significant effects by time but not by groups. Whereas left and right part of static foot pressure showed no significant effects. And dynamic foot pressure showed significant effects by time but not by group also. In conclusion, it is approved that this exercise was helpful on abnormal posture arrangement and improvement of unbalanced muscle capability.

• 설비공학논문집
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• 제14권12호
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• pp.1031-1038
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• 2002

The effects of casing shape on the performance and interaction between the impeller and casing in a small-size turbo-compressor are investigated. Numerical analysis is conducted for the compressor with circular and single volute casings from inlet to discharge nozzle. In order to predict the flow pattern inside the entire impeller, vaneless diffuer and casing, calculations with multiple frames of reference method between the rotating and stationery parts of the domain are carried out. For compressible turbulent flow fields, the continuity and three-dimensional time-averaged Wavier-Stokes equations are employed. To evaluate the performance of two types of casings, the static pressure and loss coefficients are obtained with various flow rates. Also, static pressure distributions around casings are studied for different casing shapes, which are very important to predict the distribution of radial load. To prove the accuracy of numerical results, measurements of static pressure around casing and pressure difference between the inlet and outlet of the compressor are peformed for the circular casing. Comparisons of these results between the experimental and numerical analyses are conducted, and reasonable agreement is obtained.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.1354-1359
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• 2007

This paper discusses the acoustic performance of simple expansion chamber using computational fluid dynamics(CFD). The CFD model consists of an axisymmetric grid with a single period sinusoid of acceptable amplitude and duration imposed at the inlet boundary condition. The time history of the static pressure is recorded at two points, one in the inlet pipe and one point in outlet pipe. The time history of the static pressure is converted to the frequency domain using Fourier Transform and the transmission loss (TL) of the muffler is obtained from the ratio of the static pressure at the inlet and outlet pipe. The transmission loss of CFD result is compared with that of the computational acoustic analysis using the boundary element method (BEM). There are some differences in two results due to the pressure drop according to the inlet and outlet pipe length. Therefore, the effects of the pressure drop to the transmission loss have to be considered.

• International Journal of Air-Conditioning and Refrigeration
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• 제11권3호
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• pp.132-139
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• 2003

The effects of casing shapes on the performance and the interaction between an impeller and a casing in a small-sized centrifugal compressor are investigated. Especially, numerical analyses are conducted for the centrifugal compressor with both a circular casing and a volute one. The optimum design for each element (i.e., impeller, diffuser and casing) is important to develop an efficient and compact compressor using alternative refrigerant as working fluids. Typical rotating speed of the compressor is in the range of 40,000∼45,000 rpm. The impeller has backswept blades due to tip clearance and a vane diffuser has wedge type. In order to predict the flow pattern inside an entire impeller, vaneless diffuser and casing, calculations with multiple frames of reference method between the rotating and stationery parts of the domain are carried out. For computations of compressible turbulent flow fields, the continuity and time-averaged Navier-Stokes equations are employed. To evaluate the performance of two types of casings, the static pressure recovery and loss coefficients are obtained for various flow rates. Also, static pressure distributions around casings are studied for different casing shapes, which are very important to predict the distribution of radial load. The static pressure around the casing and pressure difference between the inlet and outlet of the compressor are measured for the circular casing.

• 대한기계학회논문집B
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• 제22권9호
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• pp.1195-1207
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• 1998

Periodic pulsations in the static pressure near turbine surfaces as blade rows move relative to each other is one of the important sources of turbine unsteadiness. The present experiment aims to investigate the effect of the static pressure pulsations on the interaction of film coolant flows from two rows of staggered holes with mainstream and its effect on film cooling heat transfer. Potential flow pulsations are generated by the rotating shutter mechanism installed downstream of the test section, The free-stream Strouhal number based on the boundary layer thickness is in the range of 0.033 - 0.33, and the amplitude of about 10-20%. Measured are time-averaged and phase-averaged velocity variations, pressure variations and temperature distributions of the flow field. Experimental conditions are identified by boundary layer measurements. Injectant behavior is characterized by the measurements of unsteady pressure in the plenum chamber and free-stream static pressure. The film cooling effectiveness is evaluated from the insulated wall temperature measurement. It has been found that bulk flow pulsation provides very large diffusion of the injectants and the effectiveness is significantly reduced by the flow pulsations.

• 동력기계공학회지
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• 제19권5호
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• pp.80-85
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• 2015

The unsteady-state, incompressible and three-dimensional large eddy simulation(LES) was carried out to analyze the structure of turbulent flow fields according to the operating loads of three-dimensional small-size axial fan(SSAF). LES shows the best prediction performance in comparison with any other Reynolds averaged Navier-Stokes(RANS) method because static pressure coefficients analysed by LES show a little bit larger than measurements including all flow coefficients. Also, it can be known that the wake of SSAF is divided into from axial flow to radial flow before and behind stall region according to the increase of static pressure through LES analysis.