• Aerospace Engineering and Technology
• /
• v.6 no.2
• /
• pp.29-34
• /
• 2007

The purpose of this paper was to address the methodology of the air flow measurement using duct mach number that was considered area-weighed average obtained by total pressure and temperature measured at engine inlet duct. Without installing boundary rake, the prediction of air flow measurement was discussed. Actual air flow measurement and pressure value using pressure loss through inlet seal were described to improve the reliability and operability of altitude engine test facility.

• Journal of the Society of Naval Architects of Korea
• /
• v.28 no.1
• /
• pp.19-26
• /
• 1991

The complete, fully-elliptic Reynolds-averaged Navier-Stokes equations have been solved using a two-layer model, in the $\kappa-\varepsilon$ turbulence model, for the axisymmetric body. Numerically generated boundary-fitted coordinate system and the finite analytic methods are used to solve the governing equations. Calculations are started after the middle body with given inlet conditions. The velocities and the turbulent quantities at the inlet section are specified by solving the boundary layer equations or by standard flat-plate boundary profiles. The effects of the inlet conditions on the solution are investigated.

• The KSFM Journal of Fluid Machinery
• /
• v.10 no.6
• /
• pp.44-49
• /
• 2007

In this paper, effects of inlet shape on the performance of a submerged cargo pump were numerically studied using a commercial CFD code CFX. The inlet shape, especially the gap between pump and suction well, is an important parameter in a point of view of performances of submerged cargo pump due to its effects on the residual and also hydraulic performance of the pump, respectively. To know the optimized gap, the overall performance degradations were calculated with the gap. In addition to that, the flow field through the gap was investigated to explain the effect of velocity non-uniformity on the performance of the pump impeller.

• Journal of the Speleological Society of Korea
• /
• v.29 no.30
• /
• pp.79-86
• /
• 1992

드문드문 펼쳐진 켄터키의 한 시골에 구부러 흘러내리는 그린천이 있다. 흐름은 유연하고, 강가에는 수목이 무성하다. 그곳 숲에 가리워진 커다란 물이 없는 동굴의 입구가 있다. 반대편에는 지평선 저쪽까지 푸른 초원이 펼쳐져 있다. 특별히 이렇다할 정도의 풍경은 아니지만, 여기에 세계 제일의 경이로운 동굴의 하나를 볼 수 있다. 이 동굴이 맘모스(매머드)동굴의 입구다. 여기서부터 전장 290km의 새끼모양의 동굴이 시작되는 것이다. 세계 최장의 동굴이다. 이 거대한 동굴은 관목이 번성한 프린트 대지와 맘모스 케이프대지, 그 사이를 침식하고 있는 호친스 계곡의 지하에까지 펼쳐진다. 10개 이상의 입구가 있고, 크고 넓은 광장, 폭넓고 긴 터널, 비뚤비뚤한 지하천이 계속된다. 수직굴은 적고, 또 낙차도 적다. 그 때문에, 물이 없는 주굴부는 이상적인 관광동굴로 개발되어 있다. 케이브대지에는 여기저기에 동굴의 일부가 관광에 이용되고 있다. 한 관광동굴에서는, 벌꿀통과 같은 동굴안을 걸어가기 위해 4시간 이상 걸린다. 프린트대지 쪽은 동굴이 복잡하고, 지금도 많은 새로운 동굴이 발견되며, 되어 지고 있다. (중략)

• Korean Journal of Environment and Ecology
• /
• v.31 no.1
• /
• pp.104-111
• /
• 2017

The construction of road tunnels and bridges have delivered driving efficiency and stability based on developed engineering technology. Tunnels have the advantage of reducing the deforested area compared with other road construction methods. Since a tunnel is an underground passageway dug through the surrounding soil/earth/rock and enclosed except for the entrance and exit, commonly at each end, it does not cause a large amount of deforestation. This study surveyed the deforested areas at each end of the tunnel by the design of the tunnel entrance and exit and forest topography to minimize the amount of deforestation caused by road construction. A survey was done on a total of 150 tunnels (300 entrances and exits) on several main roads in Korea. The deforested area of each tunnel was collected by a breakdown of the entrance area and the upper area of the tunnel. According to the results of Kruskal-Wallis analysis, it was found that there was statistically a significant relation between the location of tunnels and the amount of deforestation by the topographical access type of the tunnels. The tunnel with 'facing orthogonal to incline' type access caused the smallest deforestation while the the tunnel with 'facing to valley' and 'parallel with incline' type accesses caused large deforestation during tunnel construction. Tunnel positioning in the light of topography can reduce the deforested area by up to 1.5ha at each tunnel.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.37 no.3
• /
• pp.267-273
• /
• 2013

In order to provide effective operating conditions for the fan in a wet cooling tower with film fill, a new program to search for the minimum fan power was developed using a model of the optimal total annual cost of the tower based on Merkel's model. In addition, a type of design map for a cooling tower was also developed. The inlet water temperature and heat load were considered as key parameters. The present program was first validated using several typical examples. The results showed that for a given heat load, a three-dimensional graph of the fan power (z-axis), mass flux of air (x-axis, minimum fan power), and inlet water temperature (y-axis, maximum of minimum fan power) showed a saddle configuration. The minimum fan power increased as the heat load increased. The conventionally known fact that the most effective cooling tower operation coincides with a high inlet water temperature and low air flow rate can be replaced by the statement that there exists an optimum mass flux of air corresponding to a minimum fan power for a given inlet water temperature, regardless of the heat load.

• The Journal of Engineering Geology
• /
• v.20 no.2
• /
• pp.147-153
• /
• 2010

Cut-off wall with a low permeability can be constructed to prevent groundwater seepage in spillway tunnel areas. Three spillway tunnels are constructed in Im-ha multipurpose dam region and three types of cut-off walls with a variety of directions and scales are designed. As a result of MODFLOW modeling to assess the effect of cut-off wall for three types, groundwater inflows to the tunnels range from 64.26 $m^3/day$ to 65.49 $m^3/day$ and also they through a cut-off wall section from a reservoir do from 44.08 $m^3/day$ to 45.31 $m^3/day$ and it does not show any significant difference among them. Therefore, a construction process and an environmental conservation rather than the effectiveness of cut-off wall need to be considered to select the best cut-off wall in this region.

• Journal of Advanced Marine Engineering and Technology
• /
• v.32 no.6
• /
• pp.869-876
• /
• 2008

A thermocompressor is the equipment which compresses a vapor to a desired discharge pressure. Since it was first used as the evacuation pump for a surface condenser, it has been widely adopted for energy saving systems due to its high working confidence. In the present study, the geometrical analysis of the shape between the jet nozzle and the diffuser inlet, the drag force was calculated by means of the integrated equation of motion and the computational fluid dynamic (CFD) package called FLUENT. The computer simulations were performed to investigate the effects by the various suction flow rates, the distance from jet nozzle outlet to the diffuser inlet and the dimensions of the diffuser inlet section through the iterative calculation. In addition, the results from the CFD analysis on the thermocompressor and the experiments were compared for the verification of the CFD results. In the case of a jet nozzle, the results from the CFD analysis showed a good agreement with the experimental results. Furthermore, in this study, a special attention was paid on the performance of the thermocompressor by varying the diffuser convergence angle of $0.0^{\circ}$, $0.5^{\circ}$, $1.0^{\circ}$, $2.0^{\circ}$, $3.5^{\circ}$ and $4.5^{\circ}$. With the increase of the diffuser convergence angle. the suction capacity was improved up to the degree of $1.0^{\circ}$ while it was decreased over the degree of $1.0^{\circ}$.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.2 no.2
• /
• pp.3-10
• /
• 2000

The compression wave produced when a high-speed train enters a tunnel propagates along the tunnel ahead of the train. The micro pressure wave related to the compression wave is a special physics phenomena created by high-speed train-tunnel interfaces. A among methods for the purpose of reducing the micro pressure wave is to delay the gradient of the compression wave by using aerodynamic structures. The objective of this paper is to determine the optimum slanted portal using the moving model rig. According to the results, the maximum value of micro pressure wave is reduced by 19.2% for the $45^{\circ}$ slanted portal installed at the entrance of the tunnel and reduced by 41.9% for the $45^{\circ}$ slanted portals at the entrance and exit of the tunnel. Also it is reduced by 34.6% for the $30^{\circ}$ slanted portals installed at the entrance and exit of the tunnel.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.28 no.6
• /
• pp.397-407
• /
• 2016

The traveling waves of the left and right of the detached breakwater are bent behind the detached breakwater by diffraction, causing phase interference, superimposed and propagated. If the direction of the waves becomes same and they head to the entrance of a port due to the geographical conditions, superimposed wave energy could influence inside of a port. In this study, we investigated the influence of the phase difference of the left and right diffraction waves generated according to the length of the detached breakwater on the wave heights in a port through numerical experiments when the detached breakwater at a port entrance is installed. From this result, it was confirmed that the wave heights in a port is increased or decreased by the influence of superimposed caused by the phase difference of the left and right diffraction waves due to the length of the detached breakwater.