School of Engineering and Sustainable Development

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Browsing School of Engineering and Sustainable Development by Author "Abdi, Rezvan"

Now showing 1 - 4 of 4
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    From Darcy to turbulent flow: Investigating flow characteristics and regime transitions in porous media
    (AIP Publishing, 2024) Abdi, Rezvan; Krzaczek, Marek; Abdi, Meisam
    This research addresses the flow characteristics within a porous medium composed of a monolayer of closely packed spheres, spanning from viscous-dominated to turbulent flow regimes. In the first part of this paper, the turbulent flow characteristics at a 30 MPa pressure drop within the domain are presented. The results are averaged across different cross-sections between the inlet and outlet. In the second part of the study, simulations are conducted with pressure drops, ranging from nearly 0 to 100 MPa. The analysis finds distinct flow patterns within the domain and provides estimations for the permeability and the inertial term coefficient. Moreover, the transition from Darcy to non-Darcy and turbulent flow is achieved through the use of different criteria. The specified geometry is suitable for validating and calibrating simplified Discrete Element Method (DEM) models coupled with Computational Fluid Dynamics (CFD). The main goal of this research is to produce a reliable benchmark to figure out the challenge of limited experimental data concerning fluid flow characteristics in densely packed granules specially subjected to high pressure conditions. To do this, representative specimens are designed, accurate simulations are conducted, and precise assessments of the results are carried out.
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    Insights into the flow characteristics during hydraulic fracturing
    (Springer Nature, 2024-12-22) Abdi, Rezvan; Krzaczek, Marek; Abdi, Meisam
    This paper presents a numerical model to study fracture propagation during water-based hydraulic fracturing. To address the computational challenges associated with the numerical model, the proposed approach employs a set of overlapping spheres arranged in a monolayer to construct a porous specimen containing pre-existing cracks. The fluid-filled cracks represent various stages of initiation and propagation of fluid-driven fracture. The high-pressure fluid flow within the fractures is considered under isothermal conditions. Unlike the conventional focus on rock fracture analysis, the presented approach focuses on flow characteristics during fracture growth. The main objective of the presented study is to provide a detailed description of the computational fluid dynamics (CFD) aspects of fracture propagation during hydraulic fracturing to aid in calibration and validation of simplified discrete element method (DEM) models coupled with CFD representing this phenomenon. Experimental validations performed in previous studies support the model’s reliability, making it useful in particular for calibration and validation of coupled 2D DEM-CFD models constructed from one layer of spheres. Obtaining experimental data for such cases is practically challenging, and the proposed model addresses the lack of reliable experimental data for hydraulic fracturing. To achieve this, representative specimens are designed, accurate simulations are conducted and precise assessments of the results are performed. Key variables such as density, pressure, velocity, porosity, and permeability were measured to facilitate the validation and calibration of future DEM-CFD studies.
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    Investigation of passive oscillations of flexible splitter plates attached to a circular cylinder
    (Elsevier, 2018-11-23) Abdi, Rezvan; Rezazadeh, Niki; Abdi, Meisam
    This paper presents a numerical study to address wake control of a circular cylinder subjected to two-dimensional laminar flow regime using single and multiple flexible splitter plates attached to the cylinder. Three different cases are presented in the study, covering cylinders with one, two and three horizontally attached splitter plates while the locations of the plates around the cylinders are varied. The length of the splitter plates was equal to the cylinder diameter and Reynolds number was 100. Due to the flexibility of the plates, the problem was modeled as a Fluid-Structure Interaction (FSI) problem and the commercial finite element software, Comsol Multiphysics, was utilized to solve this problem using Arbitrary Lagrangian–Eulerian (ALE) method. Vortex shedding frequency and fluid forces acting on the cylinder are investigated, along with a comprehensive parametric study to identify the optimum arrangement of the plates for maximum drag reduction and maximum vortex shedding frequency reduction. The numerical results associated to the flexible splitter plates are also compared with the corresponding rigid splitter plate cases investigated in a previous study. Moreover, the tip amplitude of the plates and the maximum strains were measured in order to find an optimum position for placing a piezoelectric polymer to harvest energy from the flow.
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    Reduction of fluid forces and vortex shedding frequency of a circular cylinder using rigid splitter plates
    (Taylor and Francis, 2017-03-31) Abdi, Rezvan; Rezazadeh, Niki; Abdi, Meisam
    This study investigates the fluid forces acting on a circular cylinder in a laminar flow regime while using a passive control strategy. Three cases including the cylinder with one, two or three rigid splitter plates attached at its rear surface were considered and the location of horizontal plates (attachment angle) was varied between 0° and 90°. A comprehensive parametric study was performed to identify the optimum arrangement of the plates using the commercial finite element software, Comsol Multiphysics. The results show that the location and the number of the plates have crucial effects on the wake control. Increasing the number of splitter plates from one to two symmetric parallel plates led to a reduction in drag force, vortex shedding frequency and fluctuation of lift force. A maximum drag reduction of 23% for dual-splitters and 15% for single-splitter was achieved, at an angle of 45° at Reynolds number 100. However, increasing the number of attached plates to three didn’t have a significant effect on flow quantities when plates of the same length were utilised. The suitability of the third plate (the middle plate) was further studied by investigating the effect of length of the plate on flow quantities.