Papers by Keyword: Water Transport

Abstract: In a complex medium, particularly soil, understanding water movement is essential for optimizing water management in agricultural and natural ecosystems. This study presents a theoretical and numerical analysis of the influence of temperature variations and root activity on water retention and redistribution in soils with variable saturation. A finite element model was developed to simulate water flow, integrating temperature-dependent hydraulic properties and dynamic root water uptake. Simulations revealed that a 10°C increase in soil temperature can reduce water content by up to 15% in the top 20 cm of soil due to increased evapotranspiration and reduced matric potential. Root water uptake responds dynamically to thermal conditions, with uptake rates increasing by around 20% under moderate warming, particularly in the upper soil layers. These results demonstrate the strong coupling between thermal gradients, root function, and soil moisture distribution. They improve our ability to predict soil-plant-atmosphere interactions under changing climatic conditions and provide valuable information for optimizing irrigation strategies and ensuring sustainable use of water.

Abstract: We discuss the heat and mass transport in unsaturated-saturated porous mediaincluding heat exchange between inltrated water and matrix. We include the thermal inuenceon hydraulic permeability and on the water expansion which changes the water saturation.This consequently inuences the hydraulic permeability.Numerical modelling includes the direct and inverse solution of the problem, where model parametersare determined. Numerical experiments require only simple input/output measurementsof suitable ow characteristics in laboratory conditions with 3D cylindrical samples.The ow model is based on Richard's strongly non-linear parabolic equation based on empiricalvan Genuchten's capillary-pressure model. The transport includes longitudinal and transversaldispersion.

Abstract: We discuss the numerical modeling of heat exchange between the infiltrated water and porous media matrix. An unsaturated-saturated flow is considered with boundary conditions reflecting the external driven forces. The developed numerical method is efficient and can be used for solving the inverse problems concerning determination of transmission coefficients for heat energy exchange inside and also on the boundary of porous media. Numerical experiments support our method.

Abstract: The article deals with an issue of length pressure losses in hose line during water transfer to fires. It compares currently used attributes of pressure losses, pressure losses by hydrodynamic laws and experimentally determined pressure losses in the hose line. It designs adjustments of the constants used for the simplified calculation parameters of water transport.

Abstract: Residual parameters of Ultra High Performance Concrete (UHPC) exposed to high temperatures were experimentally accessed. The UHPC was provided by hybrid fibre reinforcement based on polyvinyl alcohol (PVA) and steel fibres. Among the studied material properties, bulk density, matrix density, total open porosity, pore size distribution, water vapour transmission and liquid water transport properties were examined. The UHPC samples were exposed to the temperatures 400 °C, 600 °C, 800 °C, and 1000 °C respectively. For comparative purposes, the reference UHPC samples cured at laboratory temperature were tested as well. Based on the obtained results, correlation between concrete structural changes and tested parameters was found out. The applied temperature load highly affected the concrete porosity, pore size, and thus both liquid and gaseous moisture transport parameters. Disintegration of concrete structure, colour change, cracking, damage of steel fibres (melting), and failure of their cohesion was apparent from optical microscopy analysis.

Abstract: In the article the possibility of lightweight cement concrete manufacturing has been presented with use of binder in which part of cement was replaced with siliceous fly ash Class F. It was used lightweight aggregate Pollytag and Keramzyt. Total amount of binder was 400 kg/m³ with w/b=0.5. Mechanical properties has been tested as well as properties affecting durability of concrete. Replacing part of cement with fly ash improved concrete resistance on chloride ion migration, reduced compressive and tensile strength of concrete and increased carbonation depth.

Abstract: Microfluidic chips have been widely used in various of areas, such as biology, chemistry, medical science and so on. As one of the key techniques of microfluidic chips, the technique of micro driven of the water has been studied by experts all around the world for years. Of all kinds of the driven methods, the power costed by bionic driven is lowest. Moreover, as xylem is the main channel to transport the water in a tree, the mechanism of water transportation has been always an important issue in the study of physiological plant ecology. In this paper, the models of a single vessel element with different pit numbers (5 pits, 10 pits and 20 pits) or diameters(4µm and 7µm) were established according to the xylem and the pits’ structure. The 3-dimensional flow distribution was analyzed by ANSYS 12.0 calculating by realizable κ-ε algorithm. The pressure distribution contours and the velocity distribution contours of a single vessel element could be obtained after calculated by the software. According to the results, the flow field in a single vessel element of the xylem was studied. In addition, the influence of pits on the pressure and velocity were analyzed. The results showed that the influence on pressure and velocity is less when the diameter is smaller. As the number of pits on the vessel increased, the influence on the distribution of pressure and velocity is greater. Based on the result of numerical simulation of vessel element, a bionic structural microfluidic chip was designed and then analyzed by ANSYS 12.0.

Abstract: The results of research of mechanical properties and selected other characteristics influencing durability of cement concretes containing cement substitutes were presented. Cement concretes performed with conventional fly ash, fluidised fly ash and their mixture were investigated. The obtained results were compared with findings registered for two types of concrete performed without cement replacements and with cement concrete containing silica fume. The results have shown that cement concrete with predetermined 28-day compressive strength of about 50 MPa and good workability may be obtained using different cement replacements. Generally, these cement concretes exhibited also favorable properties related to concrete durability, i.e. low permeability and sorptivity, and significant reduction of chloride migration coefficient. Favourable results were obtained for cement concrete containing mix of conventional and fluidised fly ashes: good workability, compressive strength after 28th day exceeding 50 MPa, low permeability of water, and low sorptivity, as well as low coefficient of chloride migration. These features were similar as for cement concrete containing silica fume.

Abstract: Mineral wool materials are widely used for thermal insulation of buildings due to their low thermal conductivity and high fire resistivity. On this account, they are popular materials for passive fire protection of buildings. Thermal insulation boards are usually provided with hydrophobic admixtures that ensure their functional properties even in the contact with moisture. In this paper we focused on investigation of hygric transport properties of hydrophilic mineral wool materials that could find application in interior thermal insulation systems as well as in desalination and drying of salt laden materials and building structures. The obtained results give evidence of the effect of fiber orientation on studied material properties and reveal that fiber orientation perpendicular to board surface is a perspective way of materials development.

Abstract: The transport of 1M NaCl water solution in three different types of sandstones is studied For basic characterization of studied materials, their chemical composition, porosity, bulk density and matrix density are accessed. The chloride transport is analyzed using two different methods. In the first one, the chloride absorption coefficient is measured on the basis of a modified sorptivity concept. The second method consists in carrying out an inverse analysis of experimentally measured moisture and chloride concentration profiles, leading to the determination of chloride diffusion coefficient as a function of chloride concentration, and moisture diffusivity as a function of moisture content. The chloride transport properties obtained for the particular studied materials are compared and the observed differences are discussed.