The transport of chloride ions in concrete structures is not only due to diffusion but also to the advective effects of water movements and capillarity, mostly present with wet-dry cycles. These last ...two phenomena are currently very poorly modelled. A new system based on optical fibres was previously developed to measure the free chloride concentration in the pore solution without damaging the material. This work aims at developing a numerical model simulating the reactive transport of chloride ions by capillarity in a cementitious material, which considers the diffusion of chloride ions and water transport by capillarity, as well as the chloride adsorption by the material with chemical interaction. It led to the analysis of the main phenomena occurring during a capillarity test. In a larger perspective, this study improves the current understanding of the durability of concrete structures exposed to severe environmental conditions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Previous studies of the effects of regional climate conditions on urban heat islands (UHIs) focused mostly on surface UHIs, whereas few considered canopy layer UHIs. In the present study, a numerical ...modeling method is used to investigate the impacts of regional climate conditions on canopy layer UHIs at the district scale while controlling for the urban morphology. The urban morphology is classified according to the local climate zone (LCZ) system as LCZ1-LCZ6. Analysis of the spatial distribution of the urban heat island intensity (UHII) show that the nighttime and daytime UHII are most significantly correlated with the air temperature and wind speed, respectively. In five typical cities, LCZ1 has the most obvious urban heat island (UHI) effect, with an average annual UHII of 1–2.3 °C, which is about 1.5 times that for LCZ4. Reducing the building density has more significant influence on mitigating the UHI effect, where reducing the building height and building density reduce the heat island degree-hours (HIdh) by about 20% and 30%, respectively. The relationships between the UHII and meteorological conditions vary among different periods. For example, the correlation between UHII and average wind speed is more significant in the winter and at night. Our results help to understand the relationships between regional climate conditions and the canopy layer UHI at the district scale.
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•Canopy layer UHIs is studied while controlling for urban morphology.•Regional climate conditions significantly affect canopy layer UHIs.•Reducing building density more conducive to alleviating UHIs.•Relationships between UHII and meteorological conditions vary among periods.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This paper aims to present a review of numerical models for the gas-steel-slag three-phase flow in gas-stirred ladles. The modeling frameworks is classified as: mixture model, interfacial model, ...multi-fluid model and Eulerian-Lagrangian (EL) model. The interfacial model is good at simulating the interfacial structure among phases, while the multi-fluid model is suited for systems consist of different kinds of phases as it separately solves the constitutive equations of each phase with modeling their interactions. Recently, the Eulerian-Lagrangian model is frequently adopted to make the discrete phase more comprehensively resolved. With coupling the interfacial model, the interfacial-Eulerian-Lagrangian (IEL) model shows a good suitability to simulate the gas-steel-slag three-phase flow, and the discrete-continuum transition, regarded as a multiscale approach, is very helpful for revealing the bubble behavior. Moreover, other phenomena including the heat and mass transfer, the erosion at the liquid-solid interface, etc. are still lack of investigation by comprehensive models.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•A numerical model is developed to predict the behaviour of a real micro-cogeneration system.•The model includes a downdraft gasifier coupled with an internal combustion engine.•The model takes into ...account gasification, cleaning, combustion and heat recovery.•The numerical model has been validated with the experimental data acquired on site.•The experimental data have been associated to their measurement uncertainties.
This work presents a numerical model developed to predict the behaviour of a real micro-cogeneration biomass gasification system, based on a fixed-bed downdraft gasifier, coupled with a spark-ignition internal combustion engine. The model developed by the authors takes into account all the thermo-physical processes occurring in the whole system: gasification, cleaning, combustion and heat recovery. The numerical model is based on the Gibbs free energy minimization, applying the restricted equilibrium method. The model has been validated with the experimental data collected during an extensive experimental campaign, and a good agreement between measured data and predicted results is obtained. The present validated model has proved to be a useful tool for analyzing the performance of real micro-CHP plants. The global electrical and thermal efficiencies predicted by the model are 19.9% and 17.8%, while the measured values are 19.5% and 21.7%, respectively. Some parametric analyses have been carried out in order to assess the performance of the system as a function of the main gasifier and engine parameters, and to predict the behaviour of the system.
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GEOZS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
•A fully-three-dimentional scouring numerical model is developed to investigate the flow and sediment motion in the grouped spur dikes system built in river engineering for the purposes of ...environmental protection and ecological conservation.•The flow properties, sediment moving and geomorphology in two sets of grouped spur dike cases with most commonly used layout styles, namely the normal-angled spur dikes case and the 45 degree downward-angled spur dikes case are discussed based on the simulation results.•The influence of flow conditions, sediment parameters and spur dike layout angles on the maximum scour depth and their coordinates are analyzed through amounts of additional simulations, which could offer guidance for the structure safety and protection project construction.•The simulations of flood passage through the spur dike fields are conducted to demonstrate the dynamic process of sediment transport and scour development under an unsteady flow condition.
The flow properties, sediment moving and geomorphology in the grouped spur dikes field have always been of interest in river engineering. In this paper, a 3D numerical model is employed to investigate the flow motion and riverbed scouring around grouped spur dikes with different layout angle styles. Series of flume experiments are introduced to verify this model’s reliability before its application on the simulation of the downward-angled spur dikes case and normal-angled spur dikes case respectively, and detailed comparative analyses on the flow intensity, vortex patterns and local scour are made for these two layout angle styles respectively, in which the similarities and differences could both be found. Then the influence of flow conditions, sediment parameters and spur dike layout angles on the maximum scour depth and their coordinates are discussed through additional simulations, while the different correlations show between the maximum scour depths with these three factors. Then the simulation of flood passage through the spur dike fields is conducted, which could not only provide river hydrological information but also offer guidance for the hydraulic structure safety.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Presents a fully three-dimensional formulation of double friction pendulum bearing.•The proposed model can consider potential uplift and impact behavior in isolation bearing.•Provides numerical ...examples to validate this model.
Friction pendulum bearings have attracted significant attention as a system to achieve multiple performance objectives under increased levels of earthquakes. Despite the tremendous progress made to develop numerical models to understand the mechanical behavior, the majority of these models still concentrate on planar behavior. Existing three-dimensional models of friction pendulum bearings usually ignore the azimuth angle of the bearing, therefore torsional resistance cannot be modeled. Moreover, important behavior such as uplift and impact cannot be included in the existing three-dimensional models. Motivated from these limitations and using double friction pendulum bearings as an example, this paper presents a three-dimensional formulation of isolation bearings which incorporates the uplift and impact behavior. Several examples are also provided to validate the proposed numerical model. The model developed in this paper will facilitate in investigations of extreme behavior of friction pendulum bearing systems or performance of these systems in buildings with novel geometries which may cause uneven displacement demands across the isolation layer.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Overviewed the molecular and crystal factors responsible for sensitivity and presented comprehensive indices correlated with sensitivity.•In particular, the recent significant progress of the ...crystal-sensitivity correlations were summarized detailly.•The determination of intrinsic structures (molecular and packing structures) on sensitivity is a challenging problem of energetic materials.•Presented an outlook of establishing the correlation models with advanced big data-based machine learning methods.
Highly efficient design on the levels of molecule and crystal, as well as formulation, is highly desired for accelerating the development of energetic materials (EMs). Sensitivity is one of the most important characteristics of EMs and should be compulsorily considered in the design. However, owing to multiple factors responsible for the sensitivity, it usually undergoes a low predictability. Thus, it becomes urgent to clarify which factors govern the sensitivity and what is the importance of these factors. The present article focuses upon the progress of the molecular and crystal correlations on the sensitivity, and the molecule-based numerical models for sensitivity prediction in the past decades. On the molecular level, composition, geometric structure, electronic structure, energy and reactivity can be correlated with the sensitivity; while the sensitivity can be also related with molecular packing pattern, intermolecular interaction, crystal morphology, crystal size and distribution, crystal surface/interface and crystal defect on the crystal level. And most of these factors, in particle on the crystal level, have been employed as variables in numerical models for predicting sensitivity of categorized EMs. Besides, we stress that more attention should be paid to the sensitivity correlations on the inherent structures of EMs, molecule and crystal packing, because they can be readily dealt by molecular simulations nowadays, facilitating to reveal the physical nature of sensitivity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Numerous estuaries worldwide have been modified in the past decades by human interventions. The shoreline and bathymetry in the Pearl River Estuary (PRE) have changed greatly over the past 40 years ...due to the influence of land reclamation and waterway dredging, which have resulted in the corresponding adjustment of its hydrodynamics. Utilizing the ROMS numerical model, this paper studies the hydrodynamic responses to changes in shoreline and bathymetry in the PRE from 1971 to 2012. The results show that, on one hand, during neap tide, the change in the shoreline makes the residual current in the West Channel (WC) increase by 0.10 (0.05) m/s at maximum in the surface (near bottom) layer. Therefore, the exchange flow increases by 9.5% and the longitudinal circulation strengthens. The surface isohalines move southward up to 18 km, but the bottom isohalines move northward ∼2 km in the WC and East Channel (EC), which is different from the previous conclusion that the seaward extension of coastlines inhibits saltwater intrusion. The decrease in salinity in the upper layer reduces the upper seaward salt transport, resulting in a larger net landward salt transport from 25.21 × 103 kg/s to 35.44 × 103 kg/s. During spring tide, the changes are relatively weaker, but the direction of salt transport changes to seaward and the net seaward transport also increases. Moreover, the change in shoreline reduces the water area and volume in the PRE by 21.3% and 15.6% respectively, which causes a reduction of 11.3% (17.1%) in tidal prism during spring (neap) tide. The wave celerity is enhanced (>23%) and the amplification of semidiurnal tide is strengthened (>20%) in the WC and West Shoal (WS). The reduction in tidal prism together with the strengthened reflection of tidal waves with a larger phase lag between elevation and velocity of M2 tidal component cause a significant decrease of 19.0% in tidal energy flux entering the PRE. However, the tidal range increases by ∼0.30 m (mainly due to the increase in M2 tidal amplitude) in the EC, which is induced by lower tidal energy dissipation there. On the other hand, during neap tide, the change in bathymetry greatly enhances the bottom landward residual current whose peak value increases by 80% in the WC, thereby increasing approximately 14 km of the intrusion distance of saline water, enhancing the exchange flow by 27.5% and strengthening the longitudinal circulation. The net landward salt transport increases to 38.39 × 103 kg/s. The results during spring tide are similar to those during neap tide but with smaller changes, and the net seaward salt transport decreases. Moreover, the wave celerity is slightly reduced (<8%) and the amplification of semidiurnal tide is also decreased (<10%) in the WC and WS. Meanwhile, the change in bathymetry only decreases the water volume by 4.7%, leading to a relatively smaller effect on the tidal prism, and it strengthens (weakens) the reflection of tidal waves in the West Shoal and Middle Shoal (WC and EC), resulting in a slight reduction in tidal energy flux entering the bay. In the WC, the tidal range is basically unchanged since the increased tidal energy flux is offset by the increased dissipation. The quantitative results obtained in this study may provide some references for the development and protection of the PRE and other estuaries that are subject to strong human interventions.
•Seaward extension of coastlines increases tidal range, wave celerity and saltwater intrusion.•Change in bathymetry increases ∼14 km of the intrusion distance of saltwater.•Change in bathymetry enhances exchange flow by 27.5%, reduces tidal energy flux by 2.4%.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The design of infrastructure that is protective against ballistic and blast fragment impact requires a series of tests which are costly. In this study, the authors propose a methodology based on a ...practical approach with the aim of facilitating the attainment of parameters of a constitutive model representative of the behavior of the main structural materials used in common constructions, namely clay or concrete, with the objective of being able to make hypotheses that are considered convenient, at a moderate cost. To this end, the proposed methodology interpolates the parameters of the target material using ballistics tests framed according to the values of related materials and compared with those existing in the literature.
Huge amounts of plastic waste are dumped into the ocean every year, forming large Garbage Patches. Countless microplastics, originating from fragmentation, weathering of larger objects or primary ...sources, pose a widespread ecological risk. In this study, the dispersion of suspended and floating microplastic particles in the East China Seas (ECSs) and adjacent seas was investigated via a coupled numerical model that included a Lagrangian particle tracking module. The role of tidal dynamics was considered in transporting the microplastic particles in the ECSs and adjacent seas. The results highlighted significant differences between the transport of suspended and floating microplastic particles. Although microplastic particles originating from different source areas followed different pathways, the Taiwan Strait, the Tokara Strait and the Tsushima Strait were identified as the major delivery channels. Of these, the Taiwan Strait played the most important role in the export of near-surface floating microplastic particles from the ECSs. The results showed that only a small fraction of the microplastic particles produced from the coastal waters of China (~18%) and Korea (~14%) entered the Pacific Ocean. However, nearly all of the microplastic particles originating from the west and south coasts of Kyushu Island entered the Pacific Ocean.
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•Tidal dynamics play a significant role in the microplastic transport in coastal oceans.•Only a small fraction of the microplastics from China enter the Pacific Ocean.•The Tsushima, Tokara, Taiwan Straits are identified as main delivery channels.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
