• 한국가시화정보학회지
• /
• 제19권3호
• /
• pp.136-142
• /
• 2021

Submerged and semi-submerged vehicles expel cooling water through an outlet. In this process, induced noise and vibration by the flow around the outlet have been reported, and it may cause problems directly related to survivability of the navy vessels. The coolant outlet has a net-type structure and circular columns are mostly used. In this study, flow measurements using PIV and LDV were performed for different type outlets; conventional (flat plate with round bar) and improved (flat and flat plate) configurations. Experiments were conducted at a cavitation tunnel where pressure and steady flow rate conditions are ensured for sufficient time to measure the flow. The average velocity field of the outlets were measured and compared through LDV measurements, and instantaneous vorticities were evaluated through PIV measurements. The results show that the improved type of the outlet is advantageous in terms of flow stability compared to the conventional type of the outlet.

• 방사성폐기물학회지
• /
• 제20권4호
• /
• pp.411-428
• /
• 2022

Given the domestic situation, all nuclear power plants are located at the seaside, where interim storage sites are also likely to be located and maritime transportation is considered inevitable. Currently, Korea does not have an independently developed maritime transportation risk assessment code, and no research has been conducted to evaluate the release rate of radioactive waste from a submerged transportation cask in the sea. Therefore, secure technology is necessary to assess the impact of immersion accidents and establish a regulatory framework to assess, mitigate, and prevent maritime transportation accidents causing serious radiological consequences. The flow rate through a gap in a containment boundary should be calculated to determine the accurate release rate of radionuclides. The fluid flow through the micro-scale gap can be evaluated by combining the flow inside and outside the transportation cask. In this study, detailed computational fluid dynamic and simplified models are constructed to evaluate the internal flow in a transportation cask and to capture the flow and heat transfer around the transportation cask in the sea, respectively. In the future, fluid flow through the gap will be evaluated by coupling the models developed in this study.

• 한국유체기계학회 논문집
• /
• 제11권6호
• /
• pp.18-23
• /
• 2008

In this paper, effects of inlet shape on the performance of a submerged cargo pump were numerically studied using a commercial CFD code ANSYS-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 investigate 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.

• 한국유체기계학회 논문집
• /
• 제10권6호
• /
• 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.

• 자원리싸이클링
• /
• 제1권1호
• /
• pp.37-43
• /
• 1992

The submerged injection smelting process was performed to recover Zn and Pb from steel dust throuth vaporization and to investigate the effect of temperature, slag composition, injection time, gas flow rate, etc. on the recoveries of valuable metals. The results show that vaporation rates of zinc and lead increased at higher temperture and higher moral ratio of ferrous to ferric oxides. In the initial stage of submerged injection of nitrogen gas, the molten slags of the dust have high value of molar ratio of $Fe^{2+}$/$Fe^{3+}$ and hence zinc and lead can be effectively recovered.

• 한국항만학회지
• /
• 제10권1호
• /
• pp.53-61
• /
• 1996

This paper describes the effect of wave control using submerged flat plate by the numerical calculation and the hydraulic model test. The boundary element method is used to develop a numerical solution for the flow field caused by monochromatic oblique waves incident upon an infinitely long, sumerged flat plate situated in arbitrary water depth. The effect of wave blocking is examined according to the change of length, submerged depth of flat plate and incident angles. Numerical results show that longer length, shallower submergence of flat plate and larger incident angles enhance the effect of wave blocking. To validate numerical analysis method, hydraulic model test was conducted in 2-D wave flume with 60 cm metal sheet. Reflected waves are extracted from water surface elevation in front of the location of a submerged plate by least square method with 3 wave gages. From comparing experimental results with numerical results, efficiency of numerical analysis method by this study could be confirmed well within wide ranges of wave frequencies.

• 대한조선학회논문집
• /
• 제49권2호
• /
• pp.203-211
• /
• 2012

The main object of this experiment is to estimate the hydrodynamic forces acting on a submerged streamlined body placed in a one-end-opened cylindrical tube moving with certain translational velocity. The best experimental design for this object is mimicking real situation, however sizes of model body and cylinder tube are just the same as those of real, for avoiding scale effects, mimicking real situation is not realizable. Hence, in this experiment, target body and cylindrical tube were designed to be towed with varying body position relative to cylindrical tube. For measuring hydrodynamic forces and flow velocity in the cylindrical tube, six one-component load cells and several one-hole Pitot tubes were used. Several conditions were checked with various end-plates those had different opening areas. Experiment results show that forces and flow velocity had different tendency with those expected, and the presence of a end-plate slows down the flow velocity in the cylindrical tube and affects pressure field in the tube to push the model submerged body forward of the tube. This tendency grows with decreasing opened area.

• 상하수도학회지
• /
• 제25권5호
• /
• pp.627-634
• /
• 2011

In the present study, the flow behaviors of square jets surface discharged and submerged discharged into shallow water were each simulated using computational fluid dynamics, and the results were compared. As for the verification of the models, the results of the hydraulic experiment conducted by Sankar, et al. (2009) were used. According to the results of the verification, the present application of computational fluid dynamics to the flow analysis of square jets discharged into shallow water was valid. As for the wall jet, which is one form of submerged discharges, at the bottom wall boundary, the peak velocity of the jet rapidly moved from the center of the jet to the bottom wall boundary due to the restriction of jet entrainment and the no-slip condition of the bottom wall boundary, and, as for the surface discharge, because jet entrainment is limited on the free water surface, the peak velocity of the jet moved from the center of the jet to the free water surface. This is because jet entrainment is restricted at the bottom wall boundary and the surface so that the momentum of the central core of the jet is preserved for considerable time at the bottom wall boundary and the surface. In addition, due to the effect of the bottom wall boundary and the free water surface, the jet discharged into shallow water had a smaller velocity diminution rate near the discharge outlet than did the free jet; at a location where it was so distant from the discharge outlet that the vertical profile of the velocity was nearly equal (b/x =20~30), moreover, it had a far smaller velocity diminution rate than did the free jet due to the effect of the finite depth.

• 대한토목학회논문집
• /
• 제44권3호
• /
• pp.329-336
• /
• 2024

우리나라에 설치된 다기능보의 경우 가동보 구간은 수문의 부분 개방 시 수문 개방 높이와 하류의 관리수위에 의해 자유도수 또는 수중도수 형태의 흐름이 발생한다. 본 연구에서는 수문 아래를 지나 흐르며 발생하는 수중도수를 수치모의하고 평균흐름, 난류량, 그리고 상대수심 등에 대하여 분석하였다. 수치모의를 위하여 unsteady Reynolds-averaged Navier-Stokes 방정식과 volume of fluid 기법, 그리고 k-ω SST 난류모형을 이용하였다. 기존에 수행된 다른 연구자들의 실험 결과를 이용하여 수치모형을 검증하여 수치모형이 도수에서 발생하는 이상흐름을 적절히 모의하는 것을 검토하였다. 또한 내부 평균흐름 및 난류량의 분포에 대하여 모의하여 분포 형태에 대해 분석하고, 자유수면과 재순환영역의 길이 등을 분석하였다.

• Journal of applied mathematics & informatics
• /
• 제17권1_2_3호
• /
• pp.73-91
• /
• 2005

The application of Green's function in calculation of flow characteristics around submerged and floating bodies due to a regular wave is presented. It is assumed that the fluid is homogeneous, inviscid and incompressible, the flow is irrotational and all body motions are small. Two methods based on the boundary integral equation method (BIEM) are applied to solve associated problems. The first is a low order panel method with triangular flat patches and uniform distribution of velocity potential on each panel. The second method is a high order panel method in which the kernels of the integral equations are modified to make it nonsingular and amenable to solution by the Gaussian quadrature formula. The calculations are performed on a submerged sphere and some floating spheroids of different aspect ratios. The excellent level of agreement with the analytical solutions shows that the second method is more accurate and reliable.