PURPOSES : In this study, a numerical clogging model that can be used to realistically visualize the movement of particles in cylindrical permeability test equipment was proposed based on the system coupling of computational fluid dynamics with the discrete element method and experimental permeability test results. This model can also be used to simulate the interaction of dust particles with bedding particles. METHODS: A 4-way system coupling method with multiphase volumes of the fluid model and porous media model was proposed. The proposed model needs to consider the influence of flow on the dust particles, interaction between the dust particles, and interaction between the dust particles and bedding layer particles. The permeability coefficient of the bedding layer in cylindrical permeability test equipment was not calculated by using the permeability test result, but was estimated by using the particle packing model and Ergun model. RESULTS : The numerical simulation demonstrated a good agreement with the experimental test results in terms of permeability and drain time. Additionally, the initial movement of particles due to the sudden drain hole opening was successfully captured by the numerical model. CONCLUSIONS : A 4-way coupling model was sufficient to simulate the water flow and particle movement in cylindrical permeability test equipment. However, additional tests and simulation are required to utilize the model for more realistic block pavement systems.

PURPOSES : In this study, a series of fundamental falling head permeability tests were conducted on a binary particle mix bedding to determine the minimum water level, bedding layer thickness, and amount of dust that can result in the stable permeability with high repeatability. The determined condition is used to develop a CFD-DEM coupled clogging model that can explain the movement of dust particles in flowing water of a block pavement system. METHODS: A binary particle mixture is utilized to experimentally simulate an ideal bedding layer of a block pavement system. To obtain a bedding layer with maximum packing degree, the well-known particle packing degree model, i.e., the modified Toufar model, was utilized. The permeability of the bedding layer for various water levels, bedding layer thicknesses, and amounts of dust was calculated. The permeability for a small water level drop was also plotted to evaluate the effect of dust on the bedding layer clogging. RESULTS: It was observed that a water level of 100 mm, bedding depth of 70 mm, and dust amount of 0.3 g result in a stable permeability condition with high repeatability. The relationship between the minimum dust amount and surface clogging of the bedding layer was suggested based on the evaluation of the volumetric calculation of the particle and void and the permeability change in the test. CONCLUSIONS: The test procedure to determine the minimum water level, bedding thickness, and dust amount was successfully proposed. The mechanism of clogging on the surface of the bedding layer was examined by relating the volumetric characteristics of dust to the clogging surface.

Desalination is a key technology to overcome water shortage problem in a near future. High energy consumption is an Achilles’ heel in desalination technology. Osmotically driven membrane processes like forward osmosis(FO) was introduced to address this energy issue. Characterizing membrane properties such as water permeability(A), salt permeability(B), and the resistance to salt diffusion within the support layer(KICP) are very important to predict the performance of scaled-up FO processes. Currently, most of researches reported that the water permeability of FO membrane was measured by reverse osmosis(RO) type test. Permeating direction of RO and FO are different and RO test needs hydraulic pressure so that several problems can be occurred(i.e. membrane deformation, compaction and effect of concentration polarization). This study focuses on measuring water permeability of FO membrane by FO type test results in various experimental conditions. A statistical approach was developed to evaluate the three FO membrane properties(A, B, and KICP) and it predicted test result by the internal and external concentration polarization model.

최근 자기치유 재료에 대한 연구는 보수하기 힘들거나, 보수비용이 많이 소요되는 구조물에 대해 구조물 스스로 손상을 치유하여 사용수명을 증가시키기 위해 많이 수행되어오고 있다. 현재 널리 사용되고 있는 자기치유 평가 방법으로는 투수시험이 있다. 하지만, 자기치유 평가 방법에서 자기치유 성능은 콘크리트의 초기 균열 폭에 큰 영향을 받지만 일관된 기준을 가지고 있지 않은 실정이다. 따라서, 본 연구에서는 기존 연구에서 사용한 균열 폭과 투수량을 기반으로 균열 폭-투수량의 상관관계와 시간-투수량의 상관관계를 분석하였다. 또한, 광학현미 경을 이용하여 측정한 초기 균열 폭은 신뢰성이 떨어지므로 Poiseuille flow에서 α값을 도출하여 시간-균열 폭에 대한 상관관계를 분석하여 시간-투수량과 시간-균열 폭에 대한 경향을 분석하였다.

Permeability is not a function of porosity alone, it depends on the porosity, pore size and distribution, and tortuosity of pore channels in concrete. There has been considerable interest in the relationship between microstructure and transport in cementitious materials, however, it is very rare to deal with the experimental study on the gas permeability coefficient of concrete. In this study, Yoon’s test was introduced. As the experiment result of gas permeability for carbonated concrete, gas permeability coefficient was successfully obtained and this was obvious for concrete with high w/c ratio