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In the current study fume extraction systems are studied numerically and the effect of various parameters as fresh air inlet gap size, fume temperature and composition as well as the dust size is investigated. To aim this goal a precise 3D model of the entire system and proper grid is generated and system of governing equations for the reactive turbulent two-phase flow is solved using a Finite-Volume based code. The results confirm that although increasing the gap size may lead to a reduction in CO volume fraction, but an increase in products temperature is inevitable. Besides, it is shown that, despite the high efficiency of settling chamber in removing the large size particles (greater than 45 micron), it has a poor efficiency in eliminating the smaller size dust particles.

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Accurate investigation of physical phenomena is one of the important challenges in engineering fields. The present study is about a wet tank which entrance of water is investigated in three cases. When the water wave moves into a tank, complex flow regimes are created. This complexity is mainly associated with different flow mechanisms during the entrance of water and propagation of waves at the bottom bed that should be modelled by means of Navier-Stokes equations with free-surface capability and in 3D phase. Due to complexity and time consuming of Navier-Stokes equations modelling, Shallow water equations are used with the assumption of hydrostatic pressure. First case is about efflux over a wet bed. Second, water influx from the middle top is investigated and then influx from top edges is modelled. A dimensionless number is introduced for each case based on water velocity, gap length and drop height which shows acceptable domain for appropriate compatibility between results. Finally, results of numerical modelling are compared with Navier-Stokes solutions which are obtained from STAR-CD software. Results show admissible compatibility with each other based on observations and inspections.

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The precision and speed of numerical simulations of physical phenomena has led to their increasing use in designing and research applications. These precision and speed are owed to the improvements in numerical methods and significant advancements in computing power of CPUs and GPUs.
Particle-based methods are some of the most recently developed numerical simulation methods. Development of these methods has been long delayed due to the need for a relatively high computational effort.
Particle-based methods can be considered as a subset of Meshless Methods. In nonlinear computational methods, mathematical equations in the problem domain are estimated only by nodes, and contrary to the case about the nodes in FEM and FDM methods, there is no need for these nodes to be connected to each other by a mesh. If the nodes are particles that carry physical properties, such as mass and stiffness, and simulations proceed on the basis of updating trajectory and physical properties of particles, then the method is called a particle-based method. Particle-based methods include molecular dynamics (MD), Discrete Element Method (DEM), Smoothed Particle Hydrodynamics (SPH), and Lattice Boltzmann Method (LBM). The number of studies and computer codes developed based on these methods has grown dramatically over the past two decades.
Among particle-based methods, DEM method is mainly used to model solid objects and fractures and in some cases it has been used to model granular materials like soil. While most of the applications of SPH method include numerical solution of the Navier-Stokes equations in fluid dynamic problems. Despite their differences, both DEM and SPH methods are particle-based methods and so there have been successful attempts to integrate them into a single application.
In current study, a computer code called “QUANTA” is introduced. In this software, the researchers have tried to integrate the SPH method with another particle-based method called Bonded Particle Method (BPM). BPM is based on DEM and was originally developed to model rock and soil mechanics phenomena. The main modification applied to DEM is the ability to consider cohesion among particles, which plays a significant role in simulating the behavior of rocks and soils.
QUANTA is being developed with the goal of providing a tool to simulate two-dimensional solid, fluid, and multi-phased interactive environments for research purposes. In this software, the solid environment is modeled using the BPM algorithm and the fluid environment is modeled using the SPH algorithm by solving Navier-Stokes equations. Depending on the problem at hand, BPM and SPH particles interact with each other by equations based on momentum or pressure. The code is developed using Visual C ++ programming language and has the ability to perform parallel computations with a remarkable speed.
To verify the software, a few simple and frequently used problems in the literature were chosen. A cantilever beam was modeled and loaded to verify BPM part of the software. Poiseuille and shear cavity problems were used to verify the SPH part. In order to verify the interaction of these two algorithms, a solid cylinder was modeled once in a wind tunnel travelling at supersonic speeds and then against the flow of a viscous fluid. According to the results of these numerical modellings, the software can be deemed successful in simulating the sample problems.
While simulation with particle methods requires more computational effort than common methods such as finite element and finite difference, the particle-based and micromechanical nature of these methods and their ability to model large-scale deformations and complex behaviors has, in many cases, made them logical choices for simulation. As the next steps of this study, the authors are developing new equations for interaction and equations of state to improve the software performance.

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Shallow sediments and large displacement of the fault in bedrock can make the fault activity may appear to be surface faulting. Propagation of the fault rupture through the soil layer is one of the hazards associated with the fault dislocation in bedrock. The ruins from the 1999 earthquakes in Turkey and Taiwan and the 2008 earthquake in Wenchuan of China clarified the effect of fault rupture on the structures located near the fault trace on the ground surface. Also, previous studies have revealed the destructive effects of the impact of surface faulting on a structure. It seems that the alluvium depth can affect the interaction between the structures and faults. Therefore, the present study used a numerical model validated with centrifuge test results to evaluate the effect of alluvium depth on the response of shallow foundation-normal fault interaction. The Mohr-Coulomb constitutive law, with internal friction angle and dilation angle softening behavior, was used to model the interaction. The alluvium depth was considered as 15, 20, 30, and 40 m. The foundation was assumed to be rigid in all cases. It was placed at different positions relative to the free field fault outcrop on the ground surface. Normal faulting also was applied pseudo-statically to the model boundaries at a dip angle of 60°. The rotation of foundation and the vertical displacement profile of the ground surface was investigated to evaluate the effect of alluvium depth on the fault rupture and foundation interaction. The results show that there is no difference between the free-field faulting zones for different alluvium depths of loose soil. A graben is formed for deeper alluvium depths of dense soil in agreement with the analytical models, although the width of faulting zones is the same for different alluvium depths. It should be noted, a graben may form in a low-angle dipping normal fault (i.e. <60°) for loose sand. In interaction models, it has been observed that the interaction mechanism of the foundation and fault remains constant for both dense and loose sands. The footwall, gapping, and hanging wall mechanisms were formed for all alluvium depths related to the position of the foundation. Also, a graben was observed as one of the hazards associated with the normal fault rupture and shallow foundation interaction in the deeper alluvium depth of dense soil. By increasing the weight of the structure, the foundation experienced more rotation for 15 and 20m alluvium depths. The reliable foundation rotation could be estimated by considering alluvium depths of 20 m and more for both dense and loose sands.

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Advancements in tunnelling technologies and ease of implementation of drilling methods in addition of other political and security issues made the construction of underground structures as an important alternative for answering the demands of population growth and the limitations of surface spaces in urban areas. Underground roads and highways, various types of tunnels and urban subway networks are the examples of underground structures being constructed and rapidly implemented in different countries. Meanwhile, for reducing negative effects to the environment, shortening the routes and improving traffic efficiency, urban tunnels should have high level of safety standards in design, construction and operation. Tunnels are considered major national projects and infrastructure investments, and huge costs are incurred around the world to build these structures. In countries located in highly active seismic zone, such as Iran, seismic researches for such important underground structures should not be ignored. The safety of such structures should be provided with respect to all loading demands and hazards issues associated with the site, including seismic loads. Reviewing seismic events in the past shows that underground structures have suffered less damage than above ground structures against seismic loads. However, in recent years, major earthquakes such as the 1995 Kobe earthquake in Japan, the 1999 Chi-Chi earthquake in Taiwan, the 1999 Kocaeli earthquake in Turkey, and the 2008 Wenchuan earthquake in China have caused underground structures to experience significant damage. There is evidence to conclude that the structural vulnerability of a tunnel in seismically active areas is an important issue but is either not yet well understood or not well assessed at the time of construction, emphasising that dynamic analysis of these structures against seismic loads is necessary. Earthquakes are likely to significantly affect tunnel performance by causing severe damage or excessive deformation of the tunnel structure. To understand the seismic-induced behaviour and performance of urban tunnels, this paper provides the state of the art in modelling studies of seismic design and assessment of tunnels. The review includes an investigation in seismic responses of real tunnels reported during past seismic events, the probable mechanisms caused damages in tunnels and physical and numerical methods used until now to either investigate those mechanisms or implemented in new designs. As an introduction, the seismic performance of tunnels affected by previous seismic events discusses first, emphasising the effective parameters in evaluation of tunnel seismic response and the relationship between the parameters, and the damage levels caused during earthquakes. Subsequently, the paper continues with a comprehensive literature review on the experimental methods used to investigate seismic-induced response in tunnels including physical testing, centrifuge tests, shaking table tests, and static tests. Analytical, quasi-static and numerical methods of dynamic analysis of tunnels and the accuracy of these methods are discussed then in details referring to some examples. The paper also reviews the effects of soil heterogeneity in the seismic response of tunnel and application of the random field for dynamic analysis of underground structures.  Examining the achievements and challenges remained in the field, the paper concludes with the existing gaps in the field to stimulate readers for doing more relevant researches.