• Title/Summary/Keyword: porous coefficient

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An Experimental Study on Performance in Elevation of Porous Polymer Concrete (투수성 폴리머 콘크리트의 성능 향상에 관한 실험적 연구)

  • Choi, Kyu-Hyung;Lho, Byeong-Cheol;Joo, Myung-Ki;Lee, Bok-Kyu
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.953-956
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    • 2008
  • The purpose of this study is to ascertain the void ratio, permeability coefficient and compressive strength of porous polymer concretes with unsaturated polyester. The porous polymer concretes using unsaturated polyester with polymer binder contents of 3.5, 4.0, 4.5 and 5.5% are prepared, and tested for void ratio, permeability coefficient and compressive strength. As a result, void ratio and permeability coefficient of porous polymer concrete decrease with increasing polymer binder content. However, the compressive strength of porous polymer concrete increase with increasing polymer binder content. The compressive strength of porous polymer concrete decrease with increasing permeability coefficient.

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Derivation and Application of Boussinesq Equations for the Wave Field in Porous Media (공극매체에서의 파동장에 대한 Boussinesq 방정식의 유도 및 적용)

  • Chun, Insik;Min, Yongchim;Lim, Hak-Soo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.35 no.5
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    • pp.1061-1071
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    • 2015
  • In the present study, the Navier-Stokes (N-S) equations delineating water flows inside porous media were derived applying Reynolds transport theorem in order to provide a basis for analyzing water wave problems inside the porous media. Then, the derived N-S equations were compared with the same species of equations in existing researches. Based on the N-S equations, a set of Boussinesq equations was then derived in such a form that the dispersiveness and nonlinearity of water waves inside the porous media can be properly reproduced. Finally, numerical analyses were carried out to demonstrate the validity of the equations. The reflection and transmission coefficients of porous breakwaters were calculated and compared with the results of existing hydraulic experiments. The numerical results showed a rather sensitive dependency on the virtual mass coefficient of grains constituting the porous media. The selection of the coefficient with zero turned out to give nice agreements with numerical and experimental results.

Effects of porous pavement on runoff reduction in Boguang subcatchment (투수성 포장도로 도입을 통한 보광배수유역 유출량 저감효과 검토)

  • Jung, Jiyun;Lee, Gunyoung;Ryu, Jaena;Ohe, Jeill
    • Journal of Korean Society of Water and Wastewater
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    • v.27 no.2
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    • pp.251-259
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    • 2013
  • Among various Green Infrastructure measures for urban stormwater management, effects of porous pavement were quantitatively examined in terms of hydrological cycle. Different scenarios for porous pavement were introduced on a SWMM model and the effects were compared and analysed using discharge hydrographs. Two types of pavements having different runoff coefficients (0.05 & 0.5) were introduced to cover different ratio of entire road areas (100 %, 77.5 % and 40.4 %) and these made up in total 6 different scenarios. Total runoff volume was reduced and peak flow was significantly decreased by applying the porous pavement. The highest reduction for total runoff was shown from S-6(covering area: 100 %, runoff coefficient: 0.05) as 19 % followed by S-5(covering area: 77.5 %, runoff coefficient: 0.05, 16 %), while that of S-2(covering area: 40.4 %, runoff coefficient: 0.05) and S-1(covering area: 40.4 %, runoff coefficient: 0.5) were the lowest with 8 % and 5 %. This proved that the application of porous pavement would improve urban hydrological cycle.

Wave-blocking Efficiency of a Horizontal Porous Flexible Membrane

  • Cho, Il-Hyoung
    • International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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    • v.6 no.1
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    • pp.7-14
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    • 2003
  • The interaction of monochromatic incident waves with a submerged horizontal porous membrane is investigated in the context of two-dimensional linear hydro-elastic theory. It is assumed that the membrane is made of material with very fine pores so that the normal velocity of the fluid passing through the porous membrane is linearly proportional to the pressure difference between two sides of the membrane (e.g. Darcy's law). Using the Eigen-function expansion method, the wave-blocking performance of a submerged horizontal porous membrane is tested with various membrane tensions, porosities, lengths, and submerged depths. It is found that an optimal combination of design parameters exists for given water depth and wave characteristics.

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Size dependent effect on deflection and buckling analyses of porous nanocomposite plate based on nonlocal strain gradient theory

  • Khazaei, Pegah;Mohammadimehr, Mehdi
    • Structural Engineering and Mechanics
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    • v.76 no.1
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    • pp.27-56
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    • 2020
  • In this paper, the deflection and buckling analyses of porous nano-composite piezoelectric plate reinforced by carbon nanotube (CNT) are studied. The equations of equilibrium using energy method are derived from principle of minimum total potential energy. In the research, the non-local strain gradient theory is employed to consider size dependent effect for porous nanocomposite piezoelectric plate. The effects of material length scale parameter, Eringen's nonlocal parameter, porosity coefficient and aspect ratio on the deflection and critical buckling load are investigated. The results indicate that the effect of porosity coefficient on the increase of the deflection and critical buckling load is greatly higher than the other parameters effect, and size effect including nonlocal parameter and the material length scale parameter have a lower effect on the deflection increase with respect to the porosity coefficient, respectively and vice versa for critical buckling load. Porous nanocomposites are used in various engineering fields such as aerospace, medical industries and water refinery.

Sloshing Damping in a Swaying Rectangular Tank Using a Porous Bulkhead (투과성 격벽을 이용한 수평 운동하는 사각형 탱크내의 슬로싱 감쇠)

  • Cho, Il-Hyoung
    • Journal of Ocean Engineering and Technology
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    • v.32 no.4
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    • pp.228-236
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    • 2018
  • The performance of a porous swash bulkhead for the reduction of the resonant liquid motion in a swaying rectangular tank was investigated based on the assumption of linear potential theory. The Galerkin method (Porter and Evans, 1995) was used to solve the potential flow model by adding a viscous frictional damping term to the free-surface condition. By comparing the experimental results and the analytical solutions, we verified that the frictional damping coefficient was 0.4. Darcy's law was used to consider the energy dissipation at a porous bulkhead. The tool that was developed with a built-in frictional damping coefficient of 0.4 was confirmed by small-scale experiments. Using this tool, the free-surface elevation, hydrodynamic force (added mass, damping coefficient) on a wall, and the horizontal load on a bulkhead were assessed for various combinations of porosity and submergence depth. It was found that the vertical porous bulkhead can suppress sloshing motions significantly when properly designed and by selecting the appropriate porosity(${\approx}0.1$) and submergence depth.

Numerical Study of Premixed Combustion within a Porous Ceramic Burner of Different Ceramic Properties (서로 다른 물성치로 이루어진 다공 세라믹 연소기 속에서의 예혼합화염 연소에 대한 수치해석 연구)

  • Lim, In-Gweon
    • Journal of the Korean Society of Combustion
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    • v.2 no.1
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    • pp.1-8
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    • 1997
  • Premixed combustion within porous ceramic media is numerically studied to understand burning characteristics and to find best configurations for burner implementations. Among many parameters, critical to burner performance, flame location and extinction coefficient are selected as major parameters for this study. The flame structure and burner performance with respect to these two parameters are observed. In the study, it is found that the location of flame is the most important in porous burner operation since it affects the rate of heat transfer and flame structure. Stability of the flame within the porous ceramic burner is discussed with respect to the flame location. It is found that to obtain high radiative output, the flame should be located downstream section of the burner. But the flame is to be unstable at most of downstream section except near the exit plane. To overcome this problem, new porous ceramic burner, using different ceramic properties in one burner instead of single property ceramic, is made and tested. With a combination of ceramics of high extinction coefficient at upstream and another material of low extinction coefficient at downstream of the burner, the flame can be stabilized at wider region of the burner with higher radiative output compared to the original burner configuration.

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A Study of Three Dimensional Flow Characteristics near the Porous Wall (다공성 방풍벽의 3차원 유동특성)

  • Kim, Sung-Hoon;Kim, Il-Hyun;Chang, Young-Bae
    • Journal of Energy Engineering
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    • v.28 no.4
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    • pp.19-28
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    • 2019
  • A study has been done on the three dimensional turbulent flow characteristic near the porous wall. The porous holes are considered by penetrating the wall in regular arrangement, and porosity is controlled by diameter of holes. Flow characteristics near the three dimensional porous wall are compared with field test results and self-generated experimental results. FLUENT is employed for computational analysis on the effect of three dimensional porosity with flow and pressure characteristics. As a result, drag coefficient is defined and compared for three dimensional effect. The drag coefficient is mostly a function of porosity, whereas the effect of Reynolds number is minimal, and its correlation is presented in terms of three dimensional porosity.

NUMERICAL ANALYSIS OF WAVE CHARACTERISTICS AROUND PERMEABLE SUBMERGED BREAKWATER ON THE POROUS SEABED (침투 해저면 위의 투과잠제주변 파랑특성의 수치해석)

  • Kim, N.H.;Woo, S.M.
    • Journal of computational fluids engineering
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    • v.19 no.3
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    • pp.8-13
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    • 2014
  • In this study, wave characteristics coming with oblique incident angle to permeable trapezoidal submerged breakwater on the porous seabed are calculated by using boundary element method. This numerical analysis, based on the wave pressure function, is analyzing the continuity in the analytical region including fluid and structure. From the comparison of the reflection coefficients and damping coefficient, the results of this study are in good agreement with the existing results. The peak values of reflection coefficient obtained by permeable trapezoidal submerged breakwater on the porous seabed are smaller than those of permeable trapezoidal submerged breakwater on the non-porous seabed. The velocity vector in front of permeable trapezoidal submerged breakwater on the porous seabed is smaller than that in front of permeable trapezoidal submerged breakwater on the non-porous seabed with out the energy loss.

Sloshing Analysis in Rectangular Tank with Porous Baffle (투과성 내부재가 설치된 사각형 탱크내의 슬로싱 해석)

  • Cho, IL-Hyoung
    • Journal of Ocean Engineering and Technology
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    • v.29 no.1
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    • pp.1-8
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    • 2015
  • An analytical model of liquid sloshing is developed to consider the energy-loss effect through a partially submerged porous baffle in a horizontally oscillating rectangular tank. The nonlinear boundary condition at the porous baffle is derived to accurately capture both the added inertia effects and the energy-loss effects from an equivalent non-linear drag law. Using the eigenfunction expansion method, the horizontal hydrodynamic force (added mass, damping coefficient) on both the wall and baffle induced by the fluid motion is assessed for various combinations of porosity, submergence depth, and the tank's motion amplitude. It is found that a negative value for the added mass and a sharp peak in the damping curve occur near the resonant frequencies. In particular, the hydrodynamic force and free surface amplitude can be largely reduced by installing the proper porous baffle in a tank. The optimal porosity of a porous baffle is near P=0.1.