Amin Ebrahimi

Amin Ebrahimi
Delft University of Technology | TU · Department of Materials Science and Engineering (MSE)

PhD

About

36
Publications
168,508
Reads
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566
Citations
Citations since 2017
23 Research Items
530 Citations
2017201820192020202120222023020406080100120
2017201820192020202120222023020406080100120
2017201820192020202120222023020406080100120
2017201820192020202120222023020406080100120
Introduction
I am a research scientist at TU Delft, performing fundamental and applied research on advanced multiscale modelling of complex heat and fluid flow problems with extensive experience covering metallurgy and materials processing (welding and additive manufacturing), thermal energy systems and Micro/Nano-fluidic devices. I utilise computer simulations and laboratory experiments to enhance our understanding of the world for the benefit of industry and society. Email: A[dot]Ebrahimi[at]tudelft[dot]nl
Additional affiliations
February 2016 - April 2020
Delft University of Technology
Position
  • PhD Student
Education
February 2016 - April 2020
Delft University of Technology
Field of study
  • Mechanical Engineering | Materials Science and Engineering | Transport Phenomena in Materials Processing
September 2012 - March 2015
Ferdowsi University Of Mashhad
Field of study
  • Aerospace Engineering | Aerodynamics and Propulsion

Publications

Publications (36)
Article
Full-text available
Direct simulation Monte Carlo (DSMC) method with simplified Bernoulli-trials (SBT) collision scheme has been used to study the rarefied pressure-driven nitrogen flow through diverging microchannels. The fluid behaviours flowing between two plates with different divergence angles ranging between 0o to 17o are described at different pressure ratios (...
Article
Full-text available
The high degree of uncertainty and conflicting literature data on the value of the permeability coefficient (also known as the mushy zone constant), which aims to dampen fluid velocities in the mushy zone and suppress them in solid regions, is a critical drawback when using the fixed-grid enthalpy-porosity technique for modelling non-isothermal pha...
Article
Full-text available
Development, optimisation and qualification of welding and additive manufacturing procedures to date have largely been undertaken on an experimental trial and error basis, which imposes significant costs. Numerical simulations are acknowledged as a promising alternative to experiments, and can improve the understanding of the complex process behavi...
Article
Full-text available
The absorptivity of a material is a major uncertainty in numerical simulations of laser welding and additive manufacturing, and its value is often calibrated through trial-and-error exercises. This adversely affects the capability of numerical simulations when predicting the process behaviour and can eventually hinder the exploitation of fully digi...
Article
Full-text available
The direct simulation Monte Carlo (DSMC) method, which is a probabilistic particle-based gas kinetic simulation approach, is employed in the present work to describe the physics of rarefied gas flow in super nanoporous materials (also known as mesoporous). The simulations are performed for different material porosities (0.5≤ϕ≤0.9), Knudsen numbers...
Thesis
The growing demand for manufactured products with complex geometries requiring advanced fusion-based manufacturing techniques emphasises the importance of process development and optimisation to reduce the risk of adverse outcomes, which is currently impeded with traditional approaches (trial and error experiments). Development, optimisation and qu...
Preprint
Full-text available
The absorptivity of a material is a major uncertainty in numerical simulations of laser welding and additive manufacturing, and its value is often calibrated through trial-and-error exercises. This adversely affects the capability of numerical simulations when predicting the process behaviour and can eventually hinder the exploitation of fully digi...
Preprint
Full-text available
One of the challenges for development, qualification and optimisation of arc welding processes lies in characterising the complex melt-pool behaviour which exhibits highly non-linear responses to variations of process parameters. The present work presents a simulation-based approach to describe the melt-pool behaviour in root-pass gas metal arc wel...
Article
Full-text available
One of the challenges for development, qualification and optimisation of arc welding processes lies in characterising the complex melt-pool behaviour which exhibits highly non-linear responses to variations of process parameters. The present work presents a computational model to describe the melt-pool behaviour in root-pass gas metal arc welding (...
Article
Full-text available
Gas flow and heat transfer in confined geometries at micro-and nanoscales differ considerably from those at macro-scales, mainly due to nonequilibrium effects such as velocity slip and temperature jump. Nonequilibrium effects increase with a decrease in the characteristic length-scale of the fluid flow or the gas density, leading to the failure of...
Article
Full-text available
Internal flow behaviour and melt-pool surface oscillations during arc welding are complex and not yet fully understood. In the present work, high-fidelity numerical simulations are employed to describe the effects of welding position, sulphur concentration (60-300 ppm) and travel speed (1.25-5 mm s-1) on molten metal flow dynamics in fully-penetrat...
Preprint
Full-text available
Gas flow and heat transfer in confined geometries at micro and nano scales differ considerably from those at macro-scales, mainly due to nonequilibrium effects such as velocity slip and temperature jump. The nonequilibrium effects enhance with a decrease in the characteristic length-scale of the fluid flow or the gas density, leading to the failure...
Preprint
Full-text available
Internal flow behaviour and melt-pool surface oscillations during arc welding are complex and not yet fully understood. In the present work, high-fidelity numerical simulations are employed to describe the effects of welding position, sulphur concentration (60-300 ppm) and travel speed (1.25-5 mm/s) on molten metal flow dynamics in fully-penetrated...
Article
Full-text available
Molten metal melt pools are characterised by highly non-linear responses, which are very sensitive to imposed boundary conditions. Temporal and spatial variations in the energy flux distribution are often neglected in numerical simulations of melt pool behaviour. Additionally, thermo-physical properties of materials are commonly changed to achieve...
Preprint
Full-text available
Molten metal melt pools are characterised by highly non-linear responses, which are very sensitive to imposed boundary conditions. Temporal and spatial variations in the energy flux distribution are often neglected in numerical simulations of melt pool behaviour. Additionally, thermo-physical properties of materials are commonly changed to achieve...
Preprint
Conjugated heat transfer and hydraulic performance for nanofluid flow in a rectangular microchannel heat sink with LVGs (longitudinal vortex generators) are numerically investigated using at different ranges of Reynolds numbers. Three-dimensional simulations are performed on a microchannel heated by a constant heat flux with a hydraulic diameter of...
Preprint
Full-text available
Heat and fluid flow in low Prandtl number melting pools during laser processing of materials are sensitive to the prescribed boundary conditions, and the responses are highly nonlinear. Previous studies have shown that fluid flow in melt pools with surfactants can be unstable at high Marangoni numbers. In numerical simulations of molten metal flow...
Article
Full-text available
Cooling of electronic devices is one of the critical challenges that the electronics industry is facing towards sustainable development. Aiming at lowering the surface temperature of the heat sink to limit thermally induced deformations, corrugated channels and nanofluids are employed to improve the thermal and hydraulic performances of a heat sink...
Preprint
Full-text available
The high degree of uncertainty and conflicting literature data on the value of the permeability coefficient (also known as the mushy zone constant), which aims to dampen fluid velocities in the mushy zone and suppress them in solid regions, is a critical drawback when using the fixed-grid enthalpy-porosity technique for modelling non-isothermal pha...
Article
Full-text available
Mixing of high-viscosity liquids (e.g. glycerol–water solutions) is challenging and costly and often requires employing active mixing methods. Two-phase flow micromixers have attracted attention due to their low cost, simple structure, and high performance. In the present work, we investigate the mixing of similar fluids with viscosities equal to o...
Article
Full-text available
Heat and fluid flow in a rectangular channel heat sink equipped with longitudinal vortex generators have been numerically investigated in the range of Reynolds numbers between 25 and 200. Aqueous solutions of carboxymethyl cellulose (CMC) with different concentrations (200–2000 ppm), which are shear-thinning non-Newtonian liquids, have been utilise...
Article
Full-text available
In this study, a flat-plate channel configured with pyramidal protrusions are numerically analysed for the first time. Simulations of laminar single-phase fluid flow and heat transfer characteristics are developed using a finite-volume approach under steady-state condition. Pure water is selected as the coolant and its thermo-physical properties ar...
Article
Full-text available
The present work is related to the study of the nitrogen gas flow through diverging micro/nano-channels. The direct simulation Monte-Carlo (DSMC) method has been used to study the flow. The Simplified Bernoulli Trials (SBT) collision scheme has been employed to reduce the computational costs and required amounts of the computer resources. The effec...
Article
Full-text available
Flow patterns and heat transfer inside mini twisted oval tubes (TOTs) heated by constant-temperature walls are numerically investigated. Different configurations of tubes are simulated using water as the working fluid with temperature-dependent thermo-physical properties at Reynolds numbers ranging between 500 and 1100. After validating the numeric...
Thesis
Full-text available
Improving the performance and decreasing the size of equipment in micro-electronics are the most important in-citation factors for sciences and economic developments in the last fifty years. In this research, the Poiseuille flow of rarefied Nitrogen gas and heat transfer in micro/nano-diverging channels is studied at various rarefication regimes. T...
Article
Full-text available
The liquid flow and conjugated heat transfer performance of single phase laminar flow in rectangular microchannels equipped with longitudinal vortex generators (LVGs) are numerically investigated. Deionized-water with temperature-dependent thermo-physical properties is employed to conduct the simulations. Three dimensional simulations are performed...
Conference Paper
A new method is presented for automatically predicting the growth of cracks in stiffened panel structures. The procedure simplifies the modelling of stiffened panels by allowing definition of beams and use of multiple overlapping boundary element zones joined by connector elements. Applications are presented to demonstrate the effect of the stiffen...

Questions

Question (1)
Question
How I can calculate the maximum mass flow rate through a circular pipe with a inner radius equals 8.5 mm when the velocity is not known? The working fluid is pure water.

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Projects

Projects (3)
Project
The goal of this research is to develop a simulation-based approach to assess melt-pool stability for welding process optimisation.
Archived project
Numerical study of gas flow and heat transfer at micro scales.
Archived project
Heat transfer enhancement in macro- and micro-channels using passive techniques.