• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2017년도 학술발표회
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• pp.384-384
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• 2017

본 연구에서는 다공성 매질에서의 비선형 흐름에 대한 수치적 분석을 수행하였다. 적용된 수치모형은 ANSYS CFX 3차원 유동해석 모형이며, 모형의 검증은 Mayer et al. (2011)에 의해 수행된 실험결과의 적용을 통해 수행되었다. 유속과 레이놀즈수-마찰계수 관계에 대한 실험결과와 수치결과를 비교한 결과 비교적 잘 일치하였다. 검증에서 적용된 실험결과를 바탕으로 투수성 계수, 점성계수 그리고 공극율의 변화에 따른 유속과 레이놀즈수-마찰계수 관계를 분석하였으며, 각각의 경우에 대해 best curve-fitting을 통해 변화 경향을 정량적으로 분석하였다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.554-565
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• 2021

Air bubble entrainment is a phenomenon that can significantly reduce the efficiency of liquid motion in piping systems. In the present study, the bubble formation mechanism in a globe valve with 90% water fraction flow is explained by visualization study and pressure oscillation analysis. The shadowgraph imaging technique is applied to illustrate the unsteady flow inside the transparent valve. This helps to study the effect of bubbles induced by the globe valve on pressure distribution and valve flow coefficient. International Society of Automation (ISA) recommends locations for measuring pressure drop of the valve to determine its flow coefficient. This paper presents the comparison of the pressures at different locations along with the upstream and the downstream of the valve with the values at recommended positions by the ISA standard. The results show that in partially filled pipe flow, the discrepancies in pressure between different measurement locations in the valve downstream are significant at valve openings less than 30%. The aerated flow induces the oscillation in pressure and flow rate, which leads to the fluctuation in the flow coefficient of the valve. The flow coefficients have a linear relationship with the Reynolds number. For the same increase of Reynolds number, the flow coefficients grow faster with larger valve openings and level off at the opening of 50%.