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Nonlinear analysis of CFSST short columns
Published in Vipulkumar Ishvarbhai Patel, Qing Quan Liang, Muhammad N. S. Hadi, Concrete-Filled Stainless Steel Tubular Columns, 2019
Vipulkumar Ishvarbhai Patel, Qing Quan Liang, Muhammad N. S. Hadi
The numerical modeling technique presented in this chapter employs the fiber element method to discretize the cross-section of a CFSST column (Liang 2009a, b, 2011a, b). The typical fiber meshes for rectangular and circular cross-sections are shown in Figures 2.6 and 2.7, respectively. The fiber analysis incorporates the beneficial influence of the strain-hardening of stainless steel in compression and tension. In the fiber simulation, the steel–concrete composite section is first divided into fine fiber elements. The origin O of the xy coordinate system coincides with the cross-section centroid. The coordinate system is utilized to define the section geometry and eccentricity of the applied axial load. Once the cross-section has been divided into small fibers, the x and y coordinates of each fiber are determined, and the fiber areas are calculated. The contribution of each fiber is summed to obtain the axial force and moments of the cross-section under compression and bending moments.
Dynamic puncture modeling of polyester needle-punched nonwoven geotextile fabrics using finite element method
Published in The Journal of The Textile Institute, 2021
Mina Sabet Eghlidi, Hasan Mashroteh, Mohammad Saleh Ahmadi, Emad Owlia
In this study, a model has been developed to simulate, and also predict the puncture behavior of the polyester needle-punched nonwoven geotextile fabrics. As far as the structural evaluation of the mechanical behavior of materials using by numerical models is concerned, the proposed model is considered based on a macro-scale due to the simplification for the user and the possibility of high speed calculations in a reasonable time. In other words, the design of the model in the microstructure (fiber simulation) greatly limits the performance of the model for the convenience and speed of work. Though the real structure of such fabrics is formed by much intense entanglements of a fibrous assembly, the simulation of fibers as well as the relevant fibers-to-fibers contact causes great complexity in the designed model; whereas, it can even vary from one needle-punched fabric to another due to their production parameters. Additionally, the software computations are so complicated and too much time consuming due to the very large number of elements and contact-type definition between them; so that, the forecasting can be impossible with common hardware features.
Effect of flow velocity on fiber efficiency and particle residence time during filtration of aqueous dispersions—An experimental and simulation study
Published in Particulate Science and Technology, 2019
Vahid Rastegar, Goodarz Ahmadi, S. V. Babu
Since a fibrous filter has an open structure, suspended particles are collected by coming into contact with a fiber and adhering to its surface by the surface forces. For dilute particle concentrations and low fiber volume fractions, the particle collection process on a single fiber does not interfere with deposition on other fibers. Therefore, in these simulations, the filtration process can be modeled as particles interacting with single fibers in their flights through the filter. In the computational model, a single fiber was placed with its axis perpendicular to the direction of the fluid flow and the flow field around the fiber was evaluated using commercial CFD software—ANSYS-FLUENT. Once the flow field was obtained, particles with diameters in the range of 35–600 nm were introduced into the flow using the discrete phase model (DPM). The trajectories were evaluated using the particle equation of motion in the Lagrangian reference frame. The default computational model of the code included all hydrodynamic forces but did not account for the surface forces. Using the C programming language, a user-defined function (UDF) was developed and compiled within the ANSYS-FLUENT code to include the hydrodynamic retardation effects and the EDL and vdW forces. A series of simulations were performed and the effects of flow velocity on particle capture as a function of particle size and zeta potential were studied. Particular attention was given to the effects of Brownian, EDL, and vdW forces on fiber collection efficiency for different flow velocities. Furthermore, the effect of velocity on minimum filtration efficiency and most penetrating particle size was also investigated. The single fiber simulation results were extended to the fibrous filter efficiency using the available empirical models. The resulting simulated filter efficiencies were compared with experiment data and a good agreement was found.