Raihan Tayeb - Academia.edu (original) (raw)

Papers by Raihan Tayeb

Machine-Learning Approach to Modeling Oxidation of Toluene in a Bubble Column Reactor

Volume 8: Fluids Engineering; Heat Transfer and Thermal Engineering, Oct 30, 2022

A feed forward machine-learning (ML) model is applied to study bubble induced turbulence and bubb... more A feed forward machine-learning (ML) model is applied to study bubble induced turbulence and bubble mass transfer in a bubble column reactor. Using direct numerical simulation data for forced turbulence, bubble deformations and flow velocities are predicted. To predict mass transfer, ML sub-grid scale (SGS) modeling technique is introduced for the concentration of reactants and products undergoing parallel competitive reactions in the oxidation of toluene. The ML model replaces the iterative approach associated with the use of analytical profiles for previous SGS models for correcting concentration profiles in boundary layers. The present model, thus, offers a significant performance bonus as well as the flexibility to extend to more complex scenarios due to its data-driven nature.

A Machine Learning Approach to Model Oxidation of Toluene in a Bubble Column Reactor

ASME Journal of Heat and Mass Transfer

A machine-learned (ML) subgrid-scale (SGS) modeling technique is introduced for efficient and acc... more A machine-learned (ML) subgrid-scale (SGS) modeling technique is introduced for efficient and accurate prediction of reactants and products undergoing parallel competitive reactions in a bubble column. The model relies on data generated from a simple substitute problem with a small number of features. The machine-learned model replaces the iterative approach associated with the use of analytical profiles for previous subgrid-scale models for correcting concentration profiles in boundary layers. The present model, thus, offers a significant performance bonus as well as the flexibility to extend to more complex scenarios due to its data-driven nature.

Numerical study of self-assembly of granular and colloidal particles

Self-assembly of granular materials and colloids are studied using several different computationa... more Self-assembly of granular materials and colloids are studied using several different computational methods such as Discrete Element Method (DEM), Smoothed Particle Hydrodynamics (SPH) method, finite volume Volume of Fluid and DEM (VOF-DEM) method and coupled VOF-Level Set and Dissipative Particle Dynamics (CVOFLS-DPD) method. A history dependent contact model is developed for the DEM and a cohesion model is introduced to study the packing of granular materials under cohesive forces. The study reveals granular size and size distribution has an important effect on the final packing structure. The study using SPH method reveals stress relaxation in a granular system subjected consecutive jamming cycles. However, above a certain initial packing fraction stress relaxation is found to be negligible. Further analysis reveals characteristics length and time scales for stress relaxation. Three-cycle basis is found to be the most preferred configuration of the particles as the granular system...

Powder Technology, 2019

The response of two-dimensional frictionless granular material to isotropic cyclic compression is... more The response of two-dimensional frictionless granular material to isotropic cyclic compression is simulated using an improved version of the Smoothed Particle Hydrodynamics (SPH) method, which includes realistic constitutive model for deformation of individual grains. The study reveals the evolution of mean coordination number and global pressure over cycles. The probability distribution function (PDF) of contact forces for different compression cycles is also reported. The global pressure at maximum compression shows downward trend for packing fractions below a certain value. The structural rearrangement that can give rise to such stress relaxation is studied by mapping relative particle mobilities and quantifying dynamic heterogeneity using a four-point susceptibility measure. The four-point susceptibility measure reveals length and time scales that can characterize the dynamics of driven system. Meso-scale structural rearrangement is studied using Falk-Langer measure of affine and non-affine deformation. The affine and non-affine deformations drop to a stable value and oscillates around it, which suggest that the structure is driving towards a more stable configuration. A negative correlation is found between the local packing fraction and the non-affine squared displacement. Finally, a complex network analysis is employed to better understand the structural rearrangement at meso-scale. The average degree and average clustering coefficient obtained from the complex network analysis show peaks at maximum compressions, but the peak values increase with cycles. The degree per particle is found to be positively correlated with local packing fraction and negatively correlated with the non-affine squared deformation. An enrichment of three-cycle population is seen, suggesting it as the most preferred conformation for particles at the meso-scale.

Numerical Simulation of Jamming Transition in Granular System Under Cyclic Compression Using Smooth Particle Hydrodynamics

Volume 2: Advanced Manufacturing, 2016

The jamming of granular materials, which indicates how disordered particle systems change from me... more The jamming of granular materials, which indicates how disordered particle systems change from mechanically unstable to stable states, has attracted significant recent interest due, but not limited, to the appearance of jamming transition or similar behavior in a broad variety of systems. Recent experiments on jamming transition have revealed the relationship between mean coordination number and packing fraction for different jammed states. In this paper the jamming states of two dimensional granular materials under cyclic compression using Smooth Particle Hydrodynamics (SPH) approach is numerically investigated. The SPH method allows one to study the stress developed within individual granular particles of arbitrary shape. In this study the granular system is cyclically and isotropically compressed or expanded. The system undergoes a range of jamming states over a large number of cycles. We measure the evolution of global pressure, mean coordination number, and packing fraction. The force chains and probability density function of force for different compression cycles are also investigated.Copyright © 2016 by ASME

Both Experimental and Numerical Investigation on Breakup Length of Cylindrical Falling Jet

Procedia Engineering, 2013

ABSTRACT The variation in breakup length of a liquid jet subjected to different physical paramete... more ABSTRACT The variation in breakup length of a liquid jet subjected to different physical parameters is investigated experimentally. The different parameters are jet velocity, Reynolds number and Weber number. Effect of gravity on breakup length is also studied. Jet breakup process is simulated numerically by solving the transient axisymmetric equations of continuity and motion using an algorithm based on the Volume of Fluid (VOF) method that was previously proven successful in simulations of steady-state liquid jets. The experimental results are compared with the numerical simulation and discrepancies are discussed. The experiment shows that the breakup length first decreases with the increase of jet velocity and then increases with much higher velocity. The simulation result shows the expected pattern of the jet breakup process with satellite drop formation and droplet oscillation as can be found in experiment. It also shows the transient variation in the jet breakup process.

Self-assembly of sub-micron particles suspended in a water film is investigated numerically. The ... more Self-assembly of sub-micron particles suspended in a water film is investigated numerically. The liquid medium is allowed to evaporate leaving only the sub-micron particles. A coupled CFD-DEM approach is used for the simulation of fluid-particle interaction. Momentum exchange and heat transfer between particles and fluid and among particles are considered. A history dependent contact model is used to compute the contact force among sub-micron particles. Simulation is done using the open source software package CFDEM which basically comprises of two other open source packages OpenFOAM and LIGGGHTS. OpenFOAM is a widely used solver for CFD related problems. LIGGGHTS, a modification of LAMMPS, is used for DEM simulation of granular materials. The final packing structure of the sub-micron particles is discussed in terms of distribution of coordination number and radial distribution function (RDF). The final packing structure shows that particles form clusters and exhibit a definite patt...

Self-assembly and packing of colloids and micro or nano scale particles has become a subject of g... more Self-assembly and packing of colloids and micro or nano scale particles has become a subject of great interest due to widespread advancement of micro-scale technologies. In this thesis, several numerical analyses are performed to study the packing or self-assembly of micro-sized particles under dry or wet condition. Part one of the thesis is concerned with DEM simulation of microsized cohesive granular particles using two history dependent contact models. The simulation results showed that the particles with Gaussian distribution always have the lowest packing density. For cohesive particles, size distributions result in the same tendency of packing density but has much less variation with particle size. In the second part a coupled CFD-DEM method is used to simulate self-assembly of micro-sized particles induced by evaporation. Interesting patterns are seen to emerge as the liquid water film evaporates. In the third part of the thesis low velocity SPH method is used to simulate jam...

Evaporation induced self-assembly of rough colloids: A multiscale simulation study

International Journal of Heat and Mass Transfer, 2021

A multiscale simulation method combining the finite volume multiphase Volume of Fluid (VOF) metho... more A multiscale simulation method combining the finite volume multiphase Volume of Fluid (VOF) method and Dissipative Particle Dynamics (DPD) is employed to investigate and control the self-assembly of charged polymeric nanoparticles in droplet solution deposited on a plane and rough substrate during solvent evaporation. The sessile droplet is placed on a constant temperature substrate and allowed to evaporate as the particles self-assemble at the bottom. The droplet temperature drops to the wet-bulb temperature during evaporation as expected. A coupling scheme between the VOF and the Level Set (LS) parameters is presented to reduce the spurious current in the droplet. An algorithm is presented for combining the coupled VOF and LS method with the DPD method. The DPD simulation includes the Derjaguin–Landau–Verwey–Overbeek (DLVO) forces between the particles, their interaction with the substrate, Stokes drag, Brownian, and capillary forces. Ring formation of particles for different cont...

Controlling Evaporation Induced Self-Assembly of Polymeric Nanoparticles: A VOF-DPD Study

Volume 8: Heat Transfer and Thermal Engineering, 2019

A mesoscopic simulation method combining multiphase Volume of Fluid (VOF) method and Dissipative ... more A mesoscopic simulation method combining multiphase Volume of Fluid (VOF) method and Dissipative Particle Dynamics (DPD) is employed to investigate and control self-assembly of charged polymeric nanoparticles in microdroplet solution deposited on plane substrate during solvent evaporation. A droplet evaporation model is first developed and validated. A coupling scheme between the CFD and the DPD simulation for particles is then presented. The DPD simulation includes the DLVO forces between the particles, their interaction with the substrate surface, Stokes drag, Brownian, and capillary forces. Numerical results show qualitative agreement with available experimental results. The proposed simulation method is expected to provide valuable tools for controlling and optimizing self-assembly of nanoparticles.

Journal of Manufacturing Science and Engineering, 2015

Granular packing structures of cohesive microsized particles with different sizes and size distri... more Granular packing structures of cohesive microsized particles with different sizes and size distributions, including monosized, uniform, and Gaussian distribution, are investigated by using two different history dependent contact models with discrete element method (DEM). The simulation is carried out in the framework of liggghts, which is a DEM simulation package extended based on branch of granular package of widely used open-source code LAMMPS. Contact force caused by translation and rotation, frictional and damping forces due to collision with other particles or container boundaries, cohesive force, van der Waals force, and gravity is considered. The radial distribution functions (RDFs), force distributions, porosities, and coordination numbers under cohesive and noncohesive conditions are reported. The results indicate that particle size and size distributions have great influences on the packing density for particle packing under cohesive effect: particles with Gaussian distrib...