• 한국해양공학회지
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• 제1권1호
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• pp.84-93
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• 1987

A beach nourishment method can be used as one of the beach erosion protection methods which may keep coastal environments whithout constructing coastal structures on the HAE UN DAE beach. The beach nourishmens is affected by a natural condition and artificial condition;a natural condition includes conditions of bottom slope, diameter of bottom materials and waves, and artificial conditions include deposit position, method, diameter and quantity of the nourishing sand. It has accomplished to obtain the deposit position and the best diameter of the nourishing sand from a two-dimensional hydraulic model test, which simulates the erosional HAE UN DAE beach. In this study, the protection of the beach erosion can be maximized when the nourishing sand of 3.3mm in diameter, which is about 5.5.times of the bottom materials in diameter, is deposited layerly in front of the breaker zone which has a water depth of 4.6m.

• 대한기계학회논문집B
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• 제25권8호
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• pp.1077-1086
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• 2001

An experimental study is performed to investigate the characteristics of vortex shedding behind a circular cylinder with serrated fins using hot-wire anemometer. Strouhal numbers which are calculated using outer diameter of a circular cylinder with serrated fins are higher than that of a circular cylinder. Fin thickness and pitch are closely related with vortex shedding frequency and play increasing or decreasing vortex shedding after transient Reynolds number. Strouhal numbers using effective diameters which are proposed in this paper agree with that of a circular cylinder. After transient Reynolds number, a trend of Strouhal number can be estimated by checking the ratio of effective diameter to inner diameter.

• 한국해양공학회지
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• 제2권1호
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• pp.163-169
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• 1988

A beach nourishment method can be used as one of the beach. The beach nourishment is affected br a natural condition and an artificial condition; a natural condtion include conditions of bottom slope, diameter of bottom materials and wave, and an artificial condition include deposit position, method, diameter and quantity of the nourishing sand. To obtain and the best diameter of the nourishing sand a two-dimensional hydraulic model test, which simulates the erosional beach, has been accmplished. In this study the protection of the beach erosion can be maximized when the nourishing sand of 0.84mm in diameter, which is about 2.5-3.5 times of the natural bottom materials in diameter.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.625-630
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• 2010

Parametric study was performed using the SCW numerical model for evaluating the performance of the SCW. The five ground related parameters, which are porosity, hydraulic conductivity, thermal conductivity, specific heat, geothermal gradient, and five SCW design parameters, which are pumping rate, well depth well diameter, dip tube diameter, bleeding rate, were used in the study. Numerical simulations were performed for short-term (24-hour) simulation. The study results indicate that the parameters that have important influence on the performance of SCW were hydraulic conductivity, thermal conductivity, geothermal gradient, pumping rate, and bleeding rate. Overall, this study showed that various factors had a cumulative influence on the performance of the SCW, and a numerical simulation can be used to accurately predict the performance of the SCW.

• 한국유체기계학회 논문집
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• 제5권1호
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• pp.27-32
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• 2002

The turbopump inducer cavitation is very important for the success of a liquid rocket engine. In this study, the performance test and cavitation performance test were carried out at various rotational speeds with two inducers of different diameter. The rotational speed was varied by 4000, 6000, and 8000 rpm, and the size effect was tested for the normal inducer and twice-enlarged one. The hydraulic performance results showed that the similarity was satisfied over the entire test range of the present study. The blade thickness effect was examined and showed that the increased blade thickness resulted in decreased efficiency and worse cavitation performance for the large tip clearance. The cavitation performance test results showed that the breakdown NPSH increased as the flow coefficient, and was not affected by the rotational speed.

• 한국안전학회지
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• 제7권2호
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• pp.42-46
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• 1992

The submersible motor pump could have much more merits than the general pump such as higher exhaustion head, narrower installahon place, lower noise due to operating in the water and so on. But, so far, hydraulic mechanism of the axial thrust at impeller was not analysed quantitatively and so it is very difficult to solve the occuring problems. Therefore, in this study, we aimed to minimize the axial thrust acting on thrust bearing of submersible motor pump through the analysis of hydraulic mechanism of thrust and design rivision of impeller. Test carried out on the pump with an impeller 92mm in diameter, 6 balacing holes 10mm in diameter, showed the thrust is reduced by about 86％ at the normal operating point.

• 동력기계공학회지
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• 제10권4호
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• pp.38-42
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• 2006

Pressure drops and friction factors in square channels with twisted tape inserts plus axial interrupted ribs are investigated. Tests are performed for Reynolds numbers ranging from 8,900 to 29,000. The rib height-to-channel hydraulic diameter, $e/D_h$, is kept at 0.057 and test section length-to-hydraulic diameter, $L/D_h$ is 30. The pressure drops and friction factor values are enhanced with axial interrupted ribs and twisted tape inserts. Square channels with twisted tape inserts plus axial interrupted ribs show the greatest pressure loss penalty in the present work. Friction factor data obtained for the square channel with twisted tape inserts plus axial interrupted ribs are less than those in the past publications for circular tubes with axial interrupted ribs and twisted tape inserts.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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• pp.54-60
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• 2002

A mini turbo-pump having 44mm diameter impeller for hydraulic power control have been tested to evaluate hydraulic performance and losses. The characteristics of the losses such as mechanical, friction, balancing rib losses were investigated. The investigation revealed that the friction loss is relatively large but the balancing rib loss small. It was found that the hydraulic efficiency of the pump at design point is very low($27\%$) due to low specific speed and large friction losses. A computational fluid dynamics(CFD) method also has been utilized for performance prediction of the mini turbo-pump to compare the computed results with the test data.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.53-56
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• 2006

The hydraulic performances of a Francis turbine which had been designed and tested by IMHEF were calculated with a commercial code and compared with the IMHEF test results. The non-dimensional specific speed of the turbine is 0.5, the runner exit diameter 0.4m and maximum efficiency 93.1% respectively. To make the calculation of the turbine more exact, the stay vanes, the guide vane, the runner and the draft tube were calculated simultaneously. The calculation results gave a quite good agreement with the IMHEF test data, and therefore it is expected that the present calculation technique will be utilized for the hydraulic design of efficient Francis turbines.

• International Journal of Fluid Machinery and Systems
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• 제2권2호
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• pp.121-126
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• 2009

The internal flow field in a centrifugal pump working at the several flow conditions has been measured by using the particle image velocimetry (PIV) technique with the laser induced fluorescence (LIF) particles and the refractive index matched (RIM) facilities. The impeller of the centrifugal pump has an outlet diameter in 100mm, and consists of six two-dimensional curvature backward swept blades of constant thickness. Measured results give reliable flow patterns in the pump. It is obvious that application of LIF particle and RIM are the key methods to obtain the right PIV measured results in pump internal flow.