• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2005년도 연구개발 발표회 논문집
• /
• pp.359-364
• /
• 2005

Centrifugal pump shows the strongest secondary flow. Wake is formed near pressure surface close to hub at impeller exit for centrifugal pump impeller. Pressure gradient drives secondary flow in the inducer region, while in the remaining region the following sources drive together: > Pressure gradient > Coriolis force Low-momentum fluid near suction surface hub moves toward pressure surface hub in mixed-flow pump impeller. Tip leakage vortex dominate secondary flow in axial-flow pump impeller. Tip leakage vortex dominate secondary flow in axial-flow in axial-flow pump impeller

• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2009년도 학술발표회 초록집
• /
• pp.1311-1315
• /
• 2009

Understanding of the hydraulics of flow is very important to support the management of river. The cross-sectional area, average velocity, flow depth and discharge can be regarded as a power function each other. In this paper the flow of Bocheong stream basin is experimentally studied. The correlation analysis was performed between observed hydraulic factors by the power type function. The constants resulted from the correlation analysis were calculated by the geomorphologic characteristics of the watershed using the power type function. The correlation coefficients between the hydraulic factors were appeared close to unit having strong correlationship. The two conditions of equality of the continuity equation were analysed, and the conditions were found to be good results. From these results the observed hydraulic data of Bocheong stream basin can be concluded as a reliable data. The correlation coefficients between the parameters of the hydraulic characteristics and geomorphologic factors were found to be close to unit.

• 소음진동
• /
• 제6권5호
• /
• pp.607-616
• /
• 1996

A combined computational fluid dynamics(CFD)-Kirchhoff method is presented for predicting high-speed impulsive noise generated by a hovering blade. Two types of Kirchhoff integral formula are used; one for the classical linear Kirchhoff formulation and the other for the nonlinear Kirchhoff formulation. An Euler finite difference solver is solved first to obtain the flow field close to the blade, and then this flow field is used as an input to a Kirchhoff formulation to predict the acoustic far-field. These formulas are used at Mach numbers of 0.90 and 0.95 to investigate the effectiveness of the linear and nonlinear Kirchhoff formulas for delocalized flow. During these calculiations, the retarded time equation is also carefully examined, in particular, for the cases of the control surface located outside of the sonic cylinder, where multiple roots are obtained. Predicted results of acoustic far-field pressure with the linear Kirchhoff formulation agree well with experimental data when the control surface is at the certain location(R=1.46), but the correlation is getting worse before or after this specific location of the control surface due to the delocalized nonlinear aerodynamic flow field. Calculations based on the nonlinear Kirchhoff equation using a linear sonic cylinder as a control surface show a reasonable agreement with experimental data in negative amplitudes for both tip Mach numbers of 0.90 and 0.95, except some computational integration problems over a shock. This concliudes that a nonlinear formulation is necessary if the control surface is close to the blade and the flow is delocalized.

• 상하수도학회지
• /
• 제23권5호
• /
• pp.517-526
• /
• 2009

This research has been conducted to investigate the characteristics of hydraulic behavior within the PAC contactor, the rectangular shape sedimentation basin without inclined tube and the other one with inclined tube those are parts of demonstration plants(capacity : $2,000m^3/d$) in Korea Institute of Water and Environment. As results of tracer tests, the flow within PAC contactor was evaluated to divided into plug flow and dead space distinctly, and characteristics of dead space was close to that of CSTR(Complete/continuous Stirred Tank Reactor). Also, considering Reynolds number, Froude number, Morill, Modal, NCSTR Inex and plug flow/mixed flow fraction, in the case of the rectangular shape sedimentation basin without inclined tube, the characteristics of flow pattern was close to CSTR. On the other hand, in the case of the basin with inclined tube, the region of CSTR decreased precisely compared with the case of no-tube. Until now we have recognized that the inclined hydraulic structure just reduces the surface loading rate within a sedimentation basin. Actually besides, the inclined structure have an important effect on the hydraulic behavior within the basin.

• Ecology and Resilient Infrastructure
• /
• 제6권3호
• /
• pp.145-153
• /
• 2019

본 연구는 저수로 변화를 통한 하천 복원이 수생 서식처에 미치는 영향을 파악하기 위하여 원주천을 대상으로 물리서식처분석을 수행하였다. 대상 어종은 원주천에 서식하는 우점종인 피라미를 대상으로 하였다. 흐름 분석은 2차원 모형인 River2D 모형을 사용하였으며, 서식처 분석은 서식처 적합도 곡선을 이용하여 서식처의 양과 질을 산정하는 서식처 적합도 모형을 사용하였다. 먼저 저수로 복원을 위하여 자연 하도에 가까운 형태로 복원을 하고 저수로 폭을 확대 및 축소하여 설계하였다. 그 결과 저수로 폭의 변화를 확대하였을 때 대상 어종의 가중가용면적은 각각 약 72% 향상되었으며, 저수로 폭을 축소하였을 때는 서식처가 약 25% 악화되는 것으로 나타났다.

• Journal of the korean society of oceanography
• /
• 제35권3호
• /
• pp.129-152
• /
• 2000

The Cheju Current (CC), defined here as a mean eastward flow in the Cheju Strait, mostly carries water of high temperature and salinity originating from the Kuroshio in winter and spring, the Cheju Warm Current Water (CWCW). The strong core of the eastward component of the CC is found close to Cheju Island (Cheju-Do, hereafter) in winter and spring with a peak speed of about 17.0 cm/s. The eastward flow weakens towards the northern Cheju Strait, and a weak westward flow occurs occasionally close to the southern coast of Korea. The volume transport ranges from 0.37 to 0.45 Sv(1 Sv=10$^6$ m$^3$/s) in winter and spring. Seasonal thermocline and harocline are formed in summer and eroded in November. The occurrence of the CWCW is confined in the southern Cheju Strait close to Cheju-Do below the seasonal thermocline in summer and fall, and cold water occupies the lower layer north of the CWCW which is thought to be brought into the area from the area west of Cheju-Do along with the CWCW. Stratification acts to increase both the speed of the CC with a peak speed of greater than 30 cm/s and the vertical shear of the along-strait currents. The strong core of the CC detached from the coast of Cheju-Do and shifted to the north during the stratified seasons. The volume transport in summer and fall ranges 0.510.66 Sv, which is about 1.5 times larger than that in winter and spring. An annual cycle of the cross-strait sea level difference shows its maximum in summer and fall and minimum in winter and spring, whose tendency is consistent with the annual variability of the CC and its transport estimated from the ADCP measurements. Moored current measurements west of Cheju-Do indicate the clockwise turning of the CC, and the moored current measurements in the Cheju Strait for 1530 days show the low-frequency variability of the along-strait flow with a period of about 37 days.

• 한국지하수토양환경학회지:지하수토양환경
• /
• 제23권1호
• /
• pp.1-13
• /
• 2018

A series of experiments using transparent micromodels with an artificial pore network etched on glass plates was performed to investigate the effects of flow rate on the migration and distribution of resident wetting porewater (deionized water) and injecting non-wetting fluid (n-hexane). Multicolored images transformed from real RGB images were used to distinguish n-hexane from porewater and pore structure. Hexane flooding followed by immiscible displacement with porewater, migration through capillary fingering, preferential flow and bypassing were observed during injection experiments. The areal displacement efficiency increases as the injection of n-hexane continues until the equilibrium reaches. Experimental results showed that the areal displacement efficiency at equilibrium increases as the flow rate increases. Close observation reveals that preferential flowpaths through larger pore bodies and throats and clusters of entrapped porewater were frequently created at lower flow rate. At higher flow rate, randomly oriented forward and lateral flowpaths of n-hexane displaces more porewater at an efficiency close to stable displacement. It may resulted from that the pore pressure of n-hexane, at higher flow rate, increases fast enough to overcome capillary pressure acting on smaller pore throats as well larger ones. Experimental results in this study may provide fundamental information on migration and distribution of immiscible fluids in subsurface porous media.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
• /
• pp.404-411
• /
• 2003

Three-dimensional vortical flow and separated flow topology near the casing wall in an axial flow fan having two different tip clearances have been investigated by a Reynolds-averaged Wavier-Stokes (RANS) flow simulation. The simulation shows that the tip leakage vortex formed close to the leading edge of the blade tip on suction side grows in the streamwise direction. On the casing wall, a separation line is formed upstream of the leakage vortex center due to the interference between the leakage vortex and main flow. The reverse flow is observed between the separation line and the attachment line generated downstream of the trailing edge, and increased with enlarging tip clearance. The patterns of a leakage velocity vector including a leakage flow rate are also analyzed according to two tip clearances. It is noted that the understanding of the distribution of a limiting streamline on the casing wall is very important to grasp the characteristics of the vortical flow in the axial flow fan.

• 신재생에너지
• /
• 제3권4호
• /
• pp.47-53
• /
• 2007

Effluent ground water overflow in deep and broad ground space building. Temperature of effluent ground water is in $12{\sim}20^{\circ}C$ annually and the quality of that water is as good as living water. Therefore if the flow rate of effluent ground water is sufficient as source of heat pump, that is good heat source and heat sink of heat pump. Effluent ground water contain the thermal energy of surrounding ground. So this is a new application of ground source heat pump. In this study open type and close type heat pump system using effluent ground water was installed and tested for a church building with large and deep ground space. The effluent flow rate of this building is $800{\sim}1000ton/day$. The heat pump capacity is 5RT each. The heat pump cooling COP is $4.9{\sim}5.2$ for the open type and $4.9{\sim}5.7$ for close type system. The system cooling COP is $3.2{\sim}4.5$ for open type and $3.8{\sim}4.2$ for close type system. This performance is up to that of BHE type ground source heat pump.

• 신재생에너지
• /
• 제3권2호
• /
• pp.40-46
• /
• 2007

Effluent ground water overflow in deep and broad ground space building. Temperature of effluent ground water is in $12{\sim}20^{\circ}...$ annually and the quality of that water is as good as well water. Therefore if the flow rate of effluent ground water is sufficient as source of heat pump, that is good heat source and heat sink of heat pump. Effuent ground water contain the thermal energy of surrounding ground. So this is a new application of ground source heat pump. In this study open type and close type heat pump system using effluent ground water was installed and tested for a church building with large and deep ground space. The effluent flow rate of this building is $800{\sim}1000\;ton/day$. The heat pump capacity is 5RT. The heat pump heating COP was $3.85{\sim}4.68$ for the open type and $3.82{\sim}4.69$ for the close type system. The system heating COP including pump power is $3.0{\sim}3.32$ for the open type and $3.32{\sim}3.84$ for close type system. This performance is up to that of BHE type ground source heat pump.