• Title/Summary/Keyword: Darcy-Stokes Flow

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An Analysis of Stokes Flow through Periodic Arrays of Cylinders Using Homogenization Theory (균질화이론을 이용한 규칙적인 배열을 갖는 실린더 집합체 사이의 점성유동 해석)

  • Seung, Yongho;Jang, Hyongil;Lee, Jinhee
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.11
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    • pp.1603-1609
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    • 1998
  • Numerical solutions of Stokes flow through periodic arrays of cylinders were sought using Darcy's law and homogenization theory. Drag and lift forces of each cylinder were computed for various attack angles and pitch-to-diameter ratios. It was found that drag force decreased as principal pressure gradient direction deviated from array direction and that drag force increased exponentially as pitch-to-diameter ratio approached unity. Similar tendency was found in lift force except that lift force increased and then decreased in quadratic manner as attack angle varied.

MHD Pulsatile Flow and Heat Transfer of Two Immiscible Couple Stress Fluids Between Permeable Beds

  • Kumar, Deepak;Agarwal, Manju
    • Kyungpook Mathematical Journal
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    • v.61 no.2
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    • pp.323-351
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    • 2021
  • The present paper addresses magnetohydrodynamic pulsating flow and heat transfer of two immiscible, incompressible, and conducting couple stress fluids between two permeable beds. The flow between the permeable beds is assumed to be governed by Stokes' [28] couple stress fluid flow equations, whereas the dynamics of permeable beds is determined by Darcy's law. In this study, matching conditions were used at the fluid-fluid interface, whereas the B-J slip boundary condition was employed at the fluid-porous interface. The governing equations were solved analytically, and the expressions for velocity, temperature, mass flux, skin friction, and rate of heat transfer were obtained. The analytical expressions were numerically evaluated, and the results are presented through graphs and tables.

Simulation of Woody Leaf Netted Venation Based on Optimization Technique (최적화기법에 의한 나뭇잎 그물맥 시뮬레이션)

  • Chen, Lei;Li, Weizheng;Jang, Gang Won;Baek, Tae Hyun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.4
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    • pp.323-329
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    • 2013
  • This study attempts to simulate the structure of a woody leaf netted venation system by using topology optimization techniques. Based on finite element method (FEM) analysis of an incompressible fluid, a topology optimal design is applied to those woody leaf netted venation models. To solve the transverse shear locking problem of a thin plate caused by the Mindlin-Reissner plate model where a leaf netted venation is assumed to be a thin plate, a P1-nonconforming element and selective reduced integration are employed. Topology optimal design is applied to multiple physical domains. Combined with the Darcy-Stokes flow problems and extended to the optimal design of fluid channels, the multiple physical models of the flow system are analyzed and venation patterns of leafs are simulated. The calculated optimal shapes are compared with the natural shapes of woody leaf venation patterns. This interdisciplinary approach may improve our understanding of the leaf venation system.

Heat transfer characteristics by an oscillating flow in a tube with a regenerator (재생기가 포함된 원관내 왕복유동에 의한 열전달 특성)

  • Lee, Geon-Tae;Gang, Byeong-Ha;Lee, Jae-Heon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.4
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    • pp.428-439
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    • 1998
  • Fluid flow and heat transfer have been numerically investigated for an oscillating flow in a tube with a regenerator. The regenerator is placed between hot and cold spaces which are heated and cooled at uniform temperature. An oscillating flow is generated by the piston motion at both ends of a tube. The time dependent, two-dimensional Navier-Stokes equations and energy equation are solved by using the finite-volume and moving grid method. The regenerator is adopted as Brinkmann-Forchheimer extended Darcy model. Numerical results are obtained for the flow and temperature fields, and described the effects of the oscillating frequency and amplitude ratio by the piston motion as well as the aspect ratio. The numerical results obtained indicate that the heat transfer between the tube wall and oscillating flow is increased as the oscillating frequency, amplitude ratio and the aspect ratio are increased.

Modeling of the filling process during resin injection/compression molding

  • Chang, Chih-Yuan
    • Advanced Composite Materials
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    • v.16 no.3
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    • pp.207-221
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    • 2007
  • The filling process of resin injection/compression molding (I/CM) can be divided into injection and compression phases. During the resin injection the mold is kept only partially closed and thus a gap is present between the reinforcements and the upper mold. The gap results in preferential flow path. After the gap is filled with the resin, the compression action initiates and forces the resin to penetrate into the fiber preform. In the present study, the resin flow in the gap is simplified by using the Stokes approximation, while Darcy's law is used to calculate the flow field in the fiber mats. Results show that most of the injected resins enter into the gap during the injection phase. The resin injection time is extremely short so the duration of the filling process is determined by the final closing action of the mold cavity. Compared with resin transfer molding (RTM), I/CM process can reduce the mold filling time or injection pressure significantly.

Numerical Modeling of Flow Characteristics within the Hyporheic Zones in a Pool-riffle Sequences (여울-소 구조에서 지표수-지하수 혼합대의 흐름 특성 분석에 관한 수치모의 연구)

  • Lee, Du-Han;Kim, Young-Joo;Lee, Sam-Hee
    • Journal of Wetlands Research
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    • v.14 no.1
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    • pp.75-87
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    • 2012
  • Hyporheic zone is a region beneath and alongside a stream, river, or lake bed, where there is mixing of shallow groundwater and surfacewater. Hyporheic exchange controls a variety of physical, biogeochemical and thermal processes, and provides unique ecotones in a aquatic ecosystem. Field and experimental observations, and modeling studies indicate that hyporheic exchange is mainly in response to pressure gradients driven by the geomorphological features of stream beds. In the reach scale of a stream, pool-riffle structures dominate the exchange patterns. Flow over a pool-riffle sequence develops recirculation zones and stagnation points, and this flow structures make irregular pressure gradient which is driving force of the hyporheic exchange. In this study, 3 D hydro-dynamic model solves the Reynolds-averaged Navier-Stokes equations for the surface water and Darcy's Law and the continuity equation for ground water. The two sets of equations are coupled via the pressure distribution along the interface. Simulation results show that recirculation zones and stagnation points in the pool-riffle structures dominantly control the upwelling and downwelling patterns. With decrease of recirculation zones, length of donwelling zone formed in front of riffles is reduced and position of maximum downwelling point moves downward. The numerical simulation could successfully predict the behavior of hyporheic exchange and contribute the field study, river management and restoration.

A Numerical Study on Beat Transfer from an Aluminum Foam Heat Sink by Impinging Air Jet in a Confined Channel (충돌 공기제트에서 국한 유로 내 발포 알루미늄 방열기의 열전달 수치해석)

  • Lee, Sang-Tae;Kim, Seo-Young;Lee, Kwan-Soo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.26 no.6
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    • pp.883-892
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    • 2002
  • A numerical study has been carried out to investigate the flow and heat transfer from an aluminum foam heat sink in a confined channel. A uniform heat flux is given at the bottom of the aluminum foam heat sink, which is horizontally placed on the heated surface. The channel walls are assumed to be adiabatic. Cold air is supplied from the top opening of the channel and exhausted to the channel outlet. Comprehensive numerical solutions are acquired to the governing Wavier-Stokes and energy equations, using the Brinkman-Forchheimer extended Darcy model and the local thermal non-equilibrium model f3r the region of porous media. Details of flow and thermal fields are examined over wide ranges of the principal parameters; i.e., the Reynolds number Re, the height of heat sink h/H, porosity $\varepsilon$and pore diameter ratio $R_{H}$.

Numerical Study on the Effect of Hyporheic Flow on Solute Transport in Surface Water (혼합대 흐름이 지표수 용질거동에 미치는 영향에 대한 수치해석 연구)

  • Jun Song Kim;Sung Hyun Jung;Donghae Baek
    • Proceedings of the Korea Water Resources Association Conference
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    • 2023.05a
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    • pp.127-127
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    • 2023
  • 지표수와 하상 경계층에서 발생하는 흐름 교환은 하천, 호소, 연안, 해안 등 자연계에 존재하는 수환경시스템에서 일반적으로 나타나는 수리학적 특성으로서, 흐름 교환이 발생하는 경계층 아래 하상층 영역을 혼합대(hyporheic zone)라 부른다. 수질오염사고 등에 의해 외부의 오염물질이 하천 내 유입될 경우, 혼합대 흐름에 의해 하상층으로 침투되고 지표수 대비 유속이 느린 하상 내 공극 흐름에 의해 거동함에 따라 이들의 하천 내 체류시간이 증가하게 된다. 따라서, 본 연구에서는 지표수와 하상 흐름을 연계한 수치해석 방법을 적용하여 혼합대가 지표수 내 용질 체류시간에 미치는 영향을 분석하였다. 먼저 연직 2차원 Reynolds 평균 Navier-Stokes(RANS) 방정식과 Darcy 방정식을 연계하여 지표수와 하상 내 흐름을 해석하였다. 지표수 영역은 RANS 방정식을 이용하여 모의하였고, 지표수 흐름해석에서 얻어진 하상의 압력장을 경계조건으로 하여 Darcy 방정식과 함께 하상 내 흐름을 모의하였다. 여기서 하상의 형태는 자연계 하천에서 일반적으로 관찰되는 사련하상(Ripple bed)으로 모사하였다. 이후, 지표수-하상 연계모의를 통해 얻어진 흐름 결과를 바탕으로 지표수-하상 경계층에서 용질거동을 모의하였다. 흐름 모의결과를 과거 실험자료와 비교한 결과, 지표수 영역 내연직흐름 분포를 정확하게 재현하였고, 동시에 혼합대 흐름 구조에 큰 영향을 미치는 지표수-하상 경계층 압력 분포 역시 관측값과 유사하게 나타났다. 용질거동 해석을 통해 얻어진 용질의 체류시간을 분석한 결과, 혼합대 흐름이 고려된 경우(투수성 하상)와 고려되지 않은 경우(불투수성 하상)를 비교했을 때 전자에서 체류시간 분포의 감수곡선이 길어지고 첨두농도가 감소하는 것으로 나타났다. 아울러, 지표수 영역의 유입부 경계의 평균 유속이 증가함에 따라 최대 체류시간이 감소하는 것으로 나타났는데, 이는 지표수-하상 경계층에서의 압력 경사가 커져 혼합대 내 유속이 증가함에 기인하는 것으로 분석되었다.

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