• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(2)
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• pp.254-259
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• 1996

The hydraulic tests for 16$\times$16 JDFA were performed to obtain the pressure loss coefficients using the FACTS. The pressure loss coefficients are calculated by converting the each properties of experimental values for inlet region, mixing vane grid, outlet region and core region by performing a power fit of the pressure loss coefficient values to the corresponding Reynolds number. The test results are compared with the existing calculated values and evaluated by using the CALOPR code in terms of pressure drop. It is turned out that the differences between the test results and the calculated values are about by 3.8% for the pressure loss coefficients and by 8.5% for the pressure drop.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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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%.

• 한국해양공학회지
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• 제21권4호
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• pp.1-7
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• 2007

Based on the eigenfunction expansion method, the wave-absorbing performance of a square or circular pile breakwater was investigated. Flow separation resulting from sudden contraction and expansion is generated and is the main cause of significant energy loss. Therefore, evaluation of an exact energy loss coefficient is critical to enhancing the reliability of the mathematical model. To obtain the energy loss coefficient, 2-dimensional turbulent flow is analyzed using the FLUENT commercial code, and the energy loss coefficient can be obtained from the pressure difference between upstream and downstream. It was found that energy loss coefficient of circular pile is 20% that of a square pile. To validate the fitting equation for the energy loss coefficient, comparison between the analytical results and the experimental results (Kakuno and Liu, 1993) was made for square and circular piles with good agreement. The array of square piles also provides better wave-absorbing efficiency than the circular piles, and the optimal porosity value is near P=0.1.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.60-68
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• 2010

In this study, the seepage flow monitoring method by hydaulic head loss rate graph was developed for the purpose of monitoring the seepage flow from the see side or from the lake on sea dike in which seepage force was varied periodically. The hydraulic head loss rate was defined in this method. The value of the rate is in the range from 0 to 1. the value of 0 means perfectly free flow of seepage. the value of 1 means perfect waterproofing. The value of coefficient of determination in the hydraulic head loss rate graph closer to 1 means that the seepage flow way is stable. The value of coefficient of determination in the hydraulic head loss rate graph closer to 0 means that the hole may exist or the piping may be in the progress. The pore water pressure data measured in Saemangeum sea dike was analyzed with the developed method The result showed that the variation of seepage flow state was detected sensitively by this method and the interception effect of sea dike could be estimated quantitatively.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 추계학술발표회논문집(1)
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• pp.295-300
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• 1996

To investigate the effects of the side-orifice on the pressure drop for single-phase flow, a series of experiments have been carried out with 16 different downstream test sections with various combinations of side-orifice shapes, different numbers of side-orifices, and different arrangements of the side-orifice using water as a working fluid. From the measurements of the pressure drop and the flow rate, the pressure loss coefficient of the side-orifice(s) has been evaluated. Based on the total number of 529 present data, an empirical correlation for the pressure loss coefficient has been developed in terms of Reynolds number and geometric parameters, such as area ratio, equivalent diameter, leading edge, and average width of side-orifice.

• 한국추진공학회지
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• 제25권6호
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• pp.29-35
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• 2021

벨 마우스 흡입구는 압력 손실이 거의 발생하지 않으며 정확한 유량 계측이 가능하다는 장점이 있어 다양한 산업에서 적용되고 있다. 본 연구에서는 벨 마우스 흡입구의 벨 형태를 Long radius 형상으로 설계하였고 야외 환경에서 엔진 운용조건에 대해 흡입되는 공기의 압력강하가 발생되는 동시에 외부 물질에 의한 엔진 손상이 발생되지 않는 적합한 보호망의 격자 사이즈를 선정하였다. 보호망 설치로 인한 전압력 손실에 대해 전산 해석 및 실험 결과 획득한 두 가지 데이터 로부터 수정된 압력 강하 계수 방정식을 제시할 수 있었다.

• 설비공학논문집
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• 제4권4호
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• pp.342-350
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• 1992

An experimental investigation of the stenosis effects on the pressure drop and flow change in the internal flow is presented. Stainless steel tubes of small diameter(3.175mm, 3.4mm) are used for the test section of the flow loop. Percent contraction ranges from 35% to 83% and the stenosis length ratio (L/d) is varied from 2.8 to 8. Water and aqueous glycerol solutions are used for Newtonian fluids and polymer solutions of Separan AP-273 (500 wppm, 1000 wppm) for non-Newtonian fluids. Pressure loss coefficients of non-Newtonian fluids decrease just as those of Newtonian fluids. The loss coefficients of Newtonian and non-Newtonian fluids increase as the percent contraction increases and the loss coefficients of non-Newtonian fluids are larger than those of Newtonian fluids for the same stenosed tube. The loss coefficient increases as the stenosis length ratio increases.

• 한국항공우주학회지
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• 제44권6호
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• pp.468-476
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• 2016

본 연구에서는 이중구조를 갖는 팬의 날개 끝에서 발생하는 손실을 저감시키기 위하여 바깥 날개 끝 익형단면을 세 축으로 회전시키는 Conic winglet을 적용하였다. 손실을 계산하기 위하여 CFD 전산해석을 수행하였으며, 최소의 손실을 얻기 위하여 최적화를 수행하였다. 최적화 결과 Conic winglet은 바깥 날개 끝의 후단 부근에서 압력면 쪽으로 휘어진 형상을 보였으며 이 형상은 날개 끝에서 발생하는 전압력 손실을 3.24 % 저감시켰다.

• 대한기계학회논문집B
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• 제25권7호
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• pp.967-974
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• 2001

Experimental investigations on the flow characteristics of downstream region of a butterfly valve, which is used in SI engine, have been conducted according to Reynolds number and valve angle. Measurement programs of the flowfield using x-type of hotwire anemometry include the mean and fluctuating velocity, turbulnet intensity, shear stress, power spectrum and pressure loss coefficient. Experimental results show that flow characteristics and independent of relatively high Reynolds number; 60,000 and 80,000. It is also seen that streamwise mean velocities have relatively large velocity gradient around the butterfly valve with increasing the valve opening angle and this trend appears even in the far downstream region. The distributions of turbulent intensity and shear stress show irregular behavior regardless of the valve opening angle and those of the case of the valve opening angle of 45°are the largest. The pressure loss coefficient of the body surface of the throttle valve increases mildly with the increase of Reynolds number and increases rapidly with the reduction of the valve opening angle.

• 대한기계학회논문집B
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• 제38권1호
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• pp.25-30
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• 2014

자동차용 터보차저 원심압축기의 오버헝 볼류트의 두 가지 타입에 대한 유동장 특성이 수치적으로 연구되었다. 볼류트의 성능을 높이기 위해서는 높은 압력회복계수와 낮은 손실계수를 갖도록 함이 필요하다. 본 연구에서는 디퓨저 입구각을 $24^{\circ}$, 질량유량을 0.055 kg/s 로 유지하고 두 가지 타입의 오버헝 볼류트에 대한 유동장 특성을 조사하였다. 하나는 1 개의 원호로 이루어진 볼류트 단면(타입 1)이며, 다른 하나는 3 개의 원호로 이루어진 볼류트 단면(타입 2)이다. 타입 2 볼류트가 타입 1 볼류트 보다 원주방향 전체를 통틀어 높은 압력회복계수와 낮은 손실계수를 보여주었다.