• Economic and Environmental Geology
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• v.41 no.6
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• pp.731-746
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• 2008

Most multiphase flow simulators following fractional flow approach assume incompressibility of fluid and matrix or consider only two phase flow (water and air, water and NAPL). However, in this study, mathematical governing equations were developed for fully compressible three-phase flow using fractional flow based approach. Also, fully compressible multiphase flow simulator (CMPS) considering compressibilities of matrix and fluid was developed using the mathematical governing equations. In order to verify CMPS, the CMPS were compared with analytical solution and the existing multiphase flow simulator, MPS, which had been developed for simulating incompressible multiphase flow (Suk and Yeh 2007; Suk and Yeh 2008). According to the results, solutions of CMPS and MPS and analytical solutions are well matched each other. Thus, it is found that CMPS has the capability of simulating compressible three phase flow phenomena assuming compressibilities of fluids and matrix.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.2
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• pp.827-833
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• 2012

In this paper, we propose an improved optical flow algorithm which reduces computational complexity as well as noise level. This algorithm reduces computational time by applying level simplification technique and removes noise by using eigenvectors of objects. Optical flow is one of the accurate algorithms used to generate depth information from two image frames using the vectors which track the motions of pixels. This technique, however, has disadvantage of taking very long computational time because of the pixel-based calculation and can cause some noise problems. The level simplifying technique is applied to reduce the computational time, and the noise is removed by applying optical flow only to the area of having eigenvector, then using the edge image to generate the depth information of background area. Three-dimensional images were created from two-dimensional images using the proposed method which generates the depth information first and then converts into three-dimensional image using the depth information and DIBR(Depth Image Based Rendering) technique. The error rate was obtained using the SSIM(Structural SIMilarity index).

• Particle and aerosol research
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• v.12 no.1
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• pp.21-26
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• 2016

In order to realize In-line and convenient measurement for solid-gas two phase flows, Light Transmission Fluctuation (LTF) based on the random variation of transmitted light intensity, light scattering theory and cross-correlation method was presented for online measurement of particle size, concentration and velocity. The statistical relationship among transmitted light intensity, particle size and particle number in measurement zone was described by Beer-Lambert Law. Accordingly, the particle size and concentration were determined from the fluctuation signal of transmitted light intensity. Simultaneously, the particle velocity was calculated by cross-correlation analysis of two neighboring light beams. By considering the influence of concentration variation in industrial applications, the improved algorithm based on spectral analysis of transmitted light intensity was proposed to improve measurement accuracy and stability. Therefore, the online measurement system based on LTF was developed and applied to measure pulverized coal in power station and raw material in cement plant. The particle size, concentration and velocity of powder were monitored in real-time. It can provide important references for optimal control, energy saving and emission reduction of energy-intensive industries.

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.6
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• pp.51-62
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• 2020

The objective of this study was to estimate an optimum ecological flow rate in the Banbyeon stream based on the two representative fish species. Hydraulic stream environment was simulated with HEC-RAS for two water flow regimes and used for the PHABSIM hydraulic simulation. A dominant species of Zacco platypus and an endemic species of Squalidus chankaensis tsuchigae were selected as the representative fishes whose habitat conditions were evaluated for the spawning and adult stages. Weighted usable area (WUA) was estimated based on habitat suitability index (HSI) and PHABSIM habitat simulation. Overall deep water zone in the stream demonstrated greater WUA which implies better habitat status. The estimated WUA for Zacco platypus as the dominant species was about five times greater than Squalidus chankaensis tsuchigae at the stream flow of 12 ㎥/s. The optimum ecological flow rates were 15 ㎥/s and 25 ㎥/s for the respective spawning and adult stages of Zacco platypus, while 5 ㎥/s was estimated for both the life cycles of Squalidus chankaensis tsuchigae. Assuming that the dominant species may survive better in wider flow regimes, the optimum ecological flow rate should be determined rater based on the endemic species and flow rate of 5 ㎥/s was suggested for the Banbyeon stream.

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.462-465
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• 2002

This paper presents a basic theory of information flow from single sending point to multiple receiving points, where new theories of algebraic system called "Hybrid Vector Space" and flow vector space play important roles. Based on the theory, a new algorithm for finding maximum homogenous information flow is proposed, where homogenous information flow means the flow of the same contents of information delivered to multiple clients at a time. Effective multi-routing algorithms fur tree-shape delivery rout search are presented.

• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.141-146
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• 2005

Flow meters in partly filled pipes are set up and run in Korea now days, but there are no standard calibration procedures for the flow meters in accordance with ISO/IEC 17025, the standard calibration procedure based on the standard calibration procedures for flow meter in closed conduits and the technical notes of flow meter's makers is developed. the measurement uncertainty of the calibration for the flow meter in partly filled pipes is evaluated.

• Journal of computational fluids engineering
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• v.14 no.2
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• pp.52-58
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• 2009

Turbulent flow past an inclined square cylinder immersed in a cross stream is numerically investigated. The angle of incidence of main flow is one of the key factors determining at which edges the flow separates. In the present study, based on comprehensive numerical simulations, effects of inclination angle on the flow characteristics are elucidated and the related physical explanation is presented.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1903-1908
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• 2004

A preconditioned numerical method for gas-liquid two-phase flows is applied to solve cavitating flow. The present method employs a finite-difference dual time-stepping integration procedure and the MUSCLTVD scheme. A homogeneous equilibrium cavitation model is used. The present density-based numerical method permits simple treatment of the whole gas-liquid two-phase flow field, including wave propagation, large density changes and incompressible flow characteristics at low Mach number. Some internal flows such as convergent-divergent nozzles are computed using this method. Comparisons of predicted and experimental results are provided and discussed.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.5
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• pp.695-702
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• 2010

Numerical analysis information will be very useful to improve fluid system. General information about an internal gas flow is presented by numerical analysis approach. Relating with hydrogen compressing system, which have an important role in hydrogen energy utilization, this should be a useful tool to observe the flow quickly and clearly. Flow characteristic analysis, including pressure and turbulence kinetic energy distribution of hydrogen gas coming to the cylinder of a reciprocating compressor are presented in this paper. Suction-passage model is designed based on real model of hydrogen compressor. Pressure boundary conditions are applied considering the real condition of operating system. The result shows pressure and turbulence kinetic energy are not distributed uniformly along the passage of the Hydrogen system. Path line or particles tracks help to demonstrate flow characteristics inside the passage. The existence of vortices and flow direction can be precisely predicted. Based on this result, the design improvement, such as reducing the varying flow parameters and flow reorientation should be done. Consequently, development of the better hydrogen compressing system will be achieved.

• Advances in aircraft and spacecraft science
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• v.1 no.1
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• pp.69-91
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• 2014

Numerical investigations are presented, which show that a back-flow flap can improve the dynamic stall characteristics of oscillating airfoils. The flap was able to weaken the stall vortex and therefore to reduce the peak in the pitching moment. This paper gives a brief insight into the method of function of a back-flow flap. Initial wind tunnel experiments were performed to define the structural requirements for a detailed experimental wind tunnel characterization. A structural integration concept and two different actuation mechanisms of a back-flow flap for a helicopter rotor blade are presented. First a piezoelectric actuation system was investigated, but the analytical model to estimate the performance showed that the displacement generated is too low to enable reliable operation. The seond actuation mechanism is based on magnetic forces to generate an impulse that initiates the opening of the flap. A concept based on two permanent magnets is further detailed and characterized, and this mechanism is shown to generate sufficient impulse for reliable operation in the wind tunnel.