Papers by Keyword: Numerical Model

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Authors: Ondrej Sikula, Martin Mohapl
Abstract: Aerated concrete from the viewpoint of the transport of liquid moisture appears to be a material with highly variable properties strongly dependent on the porosity and liquid water exposure conditions. Saturation degree of aerated concrete strongly affects not only all its thermal-technical properties, but regarding to the risk freezing, also the strength properties. To predict the degree of saturation and moisture distribution, we used certain mathematical and physical methods supplemented with experimentally identified parameters. The aim of this paper is to discuss existing approaches to model capillary moisture transport in aerated concrete and description of the new, simplified 2D computer mathematical-physical model for the solution of this phenomenon. The results of the model are compared with experiments carried out. The conclusion discusses the limits of this new model, and mentions further possibilities for its improvement.
Authors: Jin Feng Dong, Yue Zhang, Wei Yu Zhang
Abstract: Hydraulic residence time (HRT) is one of the key design parameters controlling the removal efficiency of contaminants and nutrients in subsurface wastewater infiltration system (SWIS). A two-dimensional axisymetric finite element software called SEEP/W was used to simulate unsaturated and saturated flow within SWIS. The paper presents a methodology by example for estimating residence time distribution (RTD) at the design stage of SWIS.
Authors: Sergio Baragetti, Stefano Cavalleri, Federico Tordini
Abstract: In this work the rolling contact fatigue (RCF) behaviour of WC/C PVD-coated and uncoated case hardened transmission gears for competition motorcycles was studied both numerically and experimentally. Finite element models of the gears were processed and a theoretical-numerical procedure was applied to the numerical results to predict their RCF life. The presence of the coating and the residual stress fields induced by the surface treatments were simulated. Besides 16NiCr11, which is the actual material of the gears analyzed, the Ti-6Al-4V alloy was also considered with the numerical models. Preliminary RCF tests were carried in both dry and lubricated condition to observe the damage on the tooth flanks with and without the presence of the coating.
Authors: Rhys Pullin, Pete T. Theobald, Karen M. Holford, S.L. Evans
Abstract: This paper reports on a method for numerically modelling acoustic emission signals in simple plate geometries using dispersion curves. It is demonstrated how, by using a known source to sensor distance, it is possible to determine the arrival of the frequencies of the individual AE modes at the sensor face. Assumptions based on sensor frequency response and the amplitude of individual modes allow for an approximation of each mode arriving at the sensor face. These modes are then summed to provide a numerical model of the expected signal. Results of the model are compared with a recorded signal and show good correlation, this is further demonstrated by comparing the wavelet transforms of the modelled and recorded signal.
Authors: Baris Sayin, Erdem Damcı
Abstract: There are mainly two approaches to improve the fire resistance of FRP systems. While the most common way is to protect or insulate the FRP systems, the other way is to use fibers and resins with better fire-performance. In this paper a numerical investigation for evaluating the fire behavior of insulated CFRP-strengthened RC beams is presented.The effects of external loading and thermal expansion of materials in both the structural and the thermal behavior of composite elements due to loading and elevated temperatures are taken into consideration in a finite element model. The validity of the numerical model isdemonstrated withthe results from an existing experimental study on insulated CFRP-strengthened RC beam. The conclusions of this investigation have been employed to predict the structural behavior of concrete structures successfully.
Authors: Agus Setyo Muntohar
Abstract: Many road and highway have been constructed over the expansive soil in Java island without proper soil improvement for the subgrade. The behavior of the column on the expansive soil needs for study numerically and large scale. In this study, a numerical analysis is performed to study the effect of swelling on the deformation of the soil stabilized column supported flexible pavement. The main focus of the research is to obtain the deformation due to swelling and vehicle loading. The methodology including comparison the differential settlement of the soil stabilized column supported flexible pavement and unsupported flexible pavement as control model. The numerical analysis was modeled using finite element method. The simulations result that the column installation to support flexible pavement reduced the heaving and differential settlement of the pavement effectively. In case the overlay was performed for rehabilitation and maintenance of the pavement, the mini-columns can be installed before the overlay works. However, the conclusions of the study were limited to the result of numerical modeling that depended on the applied material model and volumetric swelling.
Authors: Xu Bo Zhou, Xu Yan, Wen Xin Sun
Abstract: The coastal circulation is one of the focuses in environmental protection. A self-adaptive numerical model of the circulation in the East China Sea (the Bohai Sea, Huanghai Sea (Yellow Sea) and East China Sea) (ECS) is established for the first time. By using a self-adaptive grid system, the grids are denser at the continental slope of the ECS. Thus, the difficult problem of applying a 3-dimensional (3D) baroclinic model with coordinate transformation at continental slope is solved. This model can be used to simulate 3D baroclinic current fields and to obtain wind-driven, thermohaline and tide-induced Lagrangian circulation.
Authors: Laura Vergani, Giorgia Gobbi, Chiara Colombo
Abstract: Pipeline working environment is characterised by corrosive conditions, able to develop hydrogen formation. The presence of atomic hydrogen localized in correspondence of crack tip, where the plastic strain reaches the maximum value, is responsible for life reduction. For this reason, it is important to estimate and predict the mechanical properties decay, in terms of toughness and crack propagation, when steel is in contact with hydrogen. Aim of this study is to develop FE models of two carbon, low-alloyed steels used in pipelines applications: X65 and F22. A complex model including three simulations steps is presented. It considers the combined effect of plastic strain and hydrogen concentration on the material toughness. The results of the model are validated by a comparison with experimental tests carried out on the two low-alloyed steel.
Authors: Qing Chun Yang, Wei Lu, Ping Li
Abstract: Deep geological disposal (DGD) is selected for the long-term confinement of high-level radioactive waste (HLW) by many countries. Safety assessment of nuclear waste disposal in a deep geological repository requires understanding and quantifying radionuclide behavior through the hosting geological formation. This paper presents a numerical model to deal with the pore water composition in bentonite barrier in the evolving geochemical environment which includes bentonite, concrete and clay in a high level radioactive waste repository designed in clay formation, the model considers the following processes: advection, diffusion, aqueous complexation, mineral dissolution/precipitation and cation exchange. Bentonite porosity changes caused by mineral dissolution/precipitation reactions are taken into account in the model. The numerical sensitivity analysis to the accessible porosity of bentonite are performed, the results illustrate that the pH in bentonite is sensitive to changes in accessible porosity of bentonite, the concentrations of aqueous species are sensitive to bentonite porosity before 1000 years, and the effective diffusion coefficient of bentonite controls the extent of high pH plume in bentonite.
Authors: Shu Ping Yi, Hai Yi Ma, Hua An Wang
Abstract: Near surface disposal of low and intermediate level radioactive waste (LILW) requires a detailed site investigation of the potential sites, in which the transport behavior of solutes in the groundwater system is one of the key processes that needed to be addressed. An investigation is undertaking for the disposal of LILW at a potential site in Southern China. In-situ test have been conducted to study the hydrogeologic characteristics of the site. Firstly, tests including pit permeability tests, injecting tests, water pressure tests, pumping tests and laboratory permeability tests have been performed according to the specific field conditions. Hydraulic conductivities for different layers of rock and soils have been calculated and their recommended values have been presented. And then in-situ dispersion tests have been performed at an area adjacent to the disposal site with non-sorbed tracers. A numerical model has been developed for the site based on data obtained during the site investigation, and has been calibrated with available measured groundwater level and measured tracer concentrations in the dispersion tests. Calibrated results indicate that the longitudinal dispersion coefficient is equal to 5.0×10-3 m2/d. Preliminary predictions have been performed for the groundwater flow and solute advection-dispersion behavior according to the design of the site, in which the center valley will be backfilled with low permeable materials. Predicted results indicate that the groundwater exhibits a lower water table and a smaller hydraulic gradient under designed site condition than under natural condition. All the tracers remain underground in the site and transport slowly mainly through advection and dispersion. Finally, conclusions for the study have been presented and the key tasks for future work have been discussed. This study provides an insight understanding of the hydrogeology characteristics of the disposal site and is useful for the assessment of environment impacts of the site under disposal of LILW.
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