• 상하수도학회지
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• 제21권4호
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• pp.421-428
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• 2007

Many engineering problems on the pipeline flow use continuity, energy, friction loss head equation. To calculate friction loss head in a pipeline, Darcy-Weisbach and many average velocity equations can be used and Hazen-Williams equation is used frequently in the pipe network for the water supply systems. Darcy-Weisbach equation is a general one acquired from applying Bernoulli's equation in the pipeline flow and Hazen-Williams equation is a experimental one in case that pipe velocity is below 3m/sec and pipe diameter is over 50mm. In this study, comparing Darcy-Weisbach with Hazen-Williams equation, relation f and C that are expressed as roughness coefficients of those equations is explained. Next, head losses calculated from using those equations are compared and those are applied in realistic pipelines. Comparing f with C, the f is decreasing linearly according to increase of the Reynolds number Re and increasing in case the C is decreasing. additionally, the C is increasing up to a point and then is decreasing according to increase of the Re. Next, the C is increasing and Re's range for increase of the C lengthens in case of decreasing of the relative roughness ${\varepsilon}/d$. Comparing head losses acquired from the two equations, head loss appears large in case that the C is decreasing and the ${\varepsilon}/d$ is increasing. additionally, Head loss calculated by the Darcy-Weisbach equation varies larger than one by Hazen-Williams equation in regard of the Re. Next, change aspect of head loss acquired by the C is distinguished more clearly than the one by the ${\varepsilon}/d$.

• 대한기계학회논문집B
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• 제41권4호
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• pp.229-238
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• 2017

본 연구는 다양한 기하학적 특성을 갖는 다공성 매질의 투과도를 유동조건의 변화와 상관없이 적절히 해석할 수 있는 일반화된 투과도 관계식을 도출하고자 시작되었다. 이에 우선, Darcy-Weisbach 관계식 (Darcy's 마찰유동관계식)의 다공질 유동에의 적용방안을 검토하였다. 결과적으로, Kozeny와 Carman 등의 선행연구를 바탕으로, Darcy-Weisbach 관계식은 다공질 유동해석에 적용이 가능하도록 확장되었다. 또한, 이는 모세관 유동모델을 바탕으로 마찰등가투과도(FEP)로 다시 정의되었다. 이때, 도출된 관계식의 유효성은 Kozeny-Carman 방정식과의 비교를 통해 검증되었고, 제시된 FEP 관계식이 Kozeny-Carman 방정식의 일반화된 형태임도 확인하였다. 결론적으로, 본 연구에서는 Darcy-Weisbach 관계식을 다공질 유동해석에 적용할 수 있도록 적절히 확장하고, 새로운 투과도 산정을 위한 FEP 관계식을 제시하였다.

• 대한수학회지
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• 제56권4호
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• pp.1083-1112
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• 2019

In this paper, we present and analyze a cell-centered collocated finite volume scheme for incompressible flows to compute solutions simultaneous to Stokes and Darcy equations by applying a pressure jump stabilization term to avoid locking. We prove that the new stabilized FV formulation satisfies a discrete inf-sup condition and error estimates for both problems. Finally, we present some numerical examples confirming this analysis.

• 상하수도학회지
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• 제19권5호
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• pp.613-618
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• 2005

In analysis of pipelines or pipe network we calculated the friction loss using Hazen-Williams or Manning formula approximately, or found one by friction coefficient from Moody diagram graphically. The friction coefficient is determined as a function of relative roughness and Reynolds number. But the calculated friction coefficient by Hazen-Williams or Manning formula considered roughness of pipe or velocity of flow. The friction coefficient in Darcy-Weisbach equation was obtained from the Moody diagram. This method is manual and is not exact from reading. This paper is presented numerical solution of Colebrook-White formula including variables of relative roughness and Reynolds number. The suggested subroutine program by an efficient linear iteration scheme can be applied to any pipe network system.

• 한국수자원학회논문집
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• 제37권8호
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• pp.613-622
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• 2004

Non-Darcy 제체내 침투수 흐름과 배수갑문을 통한 흐름의 특성을 고려한 최종체절의 수리특성분석 모형에 의한 해석결과는 실측자료와 잘 일치하여 개발된 모형의 적용성이 있음을 보여주었다. 실측치와의 비교에서 본간(1985) 식에 의한 계산결과가 나정우(1987)에 의한 방법보다 비교적 정확함을 보여주었다. 아울러 완전 또는 불완전 월류의 구분이 없이 완전월류식에 잠수도를 이용한 유량계수식을 사용한 나정우 식의 사용성을 보여 주었다. 본간 식과 나정우 식에 의한 계산 값이 실측치보다는 유출입 특성이 크게 나타나 현장에서 체절구간의 불규칙적인 단면 양상을 감안한 유량계수의 조정이 필요할 것으로 판단된다. 일반적으로 최종체절의 수리특성 분석에서 제체구간의 침투수 흐름의 고려는 Darcy 흐름에 기초하여 분석하여왔다. 제체내 침투수의 유량과 개방구간을 통과하는 유량의 비가 체절구간이 좁을수록 크게 나타나, 제체내 침투수의 정확한 해석에 의한 체절구간의 수리특성을 분석해야할 필요가 있다.

• Journal of Mechanical Science and Technology
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• 제17권10호
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• pp.1583-1596
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• 2003

A study of forced convection in a circular pipe with a partially filled porous medium was numerically investigated. The Brinkman-Forchheimer extension of the Darcy model was used to analyze the and temperature distribution in the porous medium. Our study includes two types of porous layer configurations: (1) a layer attached at the tube wall extending inward towards the centerline and (2) a layer at the centerline extending outward. The effect of several parameters, such as Darcy number, effective viscosity, effective thermal conductivity, and inertia parameter, as well as the effect of geometric parameters, were investigated.

• Korean Chemical Engineering Research
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• 제53권6호
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• pp.814-817
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• 2015

A new ionic mass transfer correlation is derived for the fluid-saturated, horizontal porous layer. Darcy-Forchheimer model is used to explain characteristics of fluid motion. Based on the microscales of turbulence a backbone mass transfer relation is derived as a function of the Darcy-Rayleigh number, $Ra_D$ and the porous medium Schmidt number, $Sc_p$. For the Darcy's limit of $Sc_p{\gg}Ra_D$, the Sherwood number, Sh is a function of $Ra_D$ only. However, for the region of high $Ra_D$, Sh can be related with $Ra_DSc_p$. Based on the present backbone equation and the electrochemical mass transfer experiments which are electro plating or electroless plating, the new ionic mass transfer correlation is suggested in the porous media.

• 한국해양공학회지
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• 제20권6호
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• pp.35-40
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• 2006

In recent years, there's been strong demand for seawalls that havea gentle slope and permeability that serveswater affinity and disaster prevention from wave attack. The aim of this study is to examine wave transformation, including wave run-up that propagates on the coastal structures. A numerical model based on the weak nonlinear dispersive Boussinesq equation, together with the unsteady nonlinear Darcy law for fluid motion in permeable layer, is developed. The applicability of this numerical model is examined through Deguchi and Moriwaki's hydraulic model test on the permeable slopes. From this study, it is found that the proposed numerical model can predict wave transformation and run-up on the gentle slope with a permeable layer, but can't show accurate results for slopes steeper than about 1:10.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.514-519
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• 2000

Predicting a pressure drop between inlet and outlet of the filter system is essential in designing the optimum filter system. This experiment has been carried out to investigate several design parameters which influence in a pressure drop, such as different tube length and metal fiber filter mesh size. A 1/50 scale filter system was made to simulate a real filter system. Results are compared with Darcy equation for a porous media.

• 물과 미래
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• 제24권1호
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• pp.109-117
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• 1991

포화-비포화 영역에서 transient흐름 해석을 위해 유체의 연속방정식과 Darcy 법칙으로부터 다공질 매체에서의 흐름 지배방정식을 유도하였다. 수치해는 가중잔차원리에 입각한 Galerkin 유한요소법으로 구하며, 시간도함수항에는 유한차분법을 적용하였다. 해석에서는 실제 자연상태에서 발생되는 부정호우자료를 이용하고 이때의 지표하 흐름 해석에 필요한 강우 주상도는 제 손실성분을 고려한 초과우량 추정모형으로부터 얻었다. 비포화 토양에서의 흐름을 고려하기 위해 투수계수, 압력수두 및 체적함수비의 상호 함수관계를 이용하였다. 모형은 대칭인 2차원으로서 비등방성, 이질 토층으로 구성하였다.