Khaled Mosharraf Mukut - Academia.edu (original) (raw)

Papers by Khaled Mosharraf Mukut

Research paper thumbnail of Physical, chemical and morphological evolution of incipient soot obtained from molecular dynamics simulation of acetylene pyrolysis

arXiv (Cornell University), Feb 9, 2024

Incipient soot particles obtained from a series of reactive molecular dynamics simulations were s... more Incipient soot particles obtained from a series of reactive molecular dynamics simulations were studied to understand the evolution of physical, chemical, and morphological properties of incipient soot. Reactive molecular dynamics simulations of acetylene pyrolysis were performed using ReaxFF potential at 1350, 1500, 1650, and 1800 K. A total of 3324 incipient soot particles were extracted from the simulations at various stages of development. Features such as the number of carbon and hydrogen atoms, number of ring structures, mass, C/H ratio, radius of gyration, surface area, volume, atomic fractal dimension, and density were calculated for each particle. The calculated values of density and C/H ratio matched well with experimental values reported in the literature. Based on the calculated features, the particles were classified in two types: type 1 and type 2 particles. It was found that type 1 particles show significant morphological evolution while type 2 particles undergo chemical restructuring without any significant morphological change. The particle volume was found to be well-correlated with the number of carbon

Research paper thumbnail of The coalescence of incipient soot clusters

Carbon, Aug 1, 2021

Abstract Reactive molecular dynamics (MD) simulations are employed to investigate the coalescence... more Abstract Reactive molecular dynamics (MD) simulations are employed to investigate the coalescence of incipient soot clusters. Initially, one thousand acetylene molecules collide and react with each other, allowing bond breakage and new bond formation upon collision, leading to various species (e.g., linear hydrocarbons, branched polyaromatic hydrocarbons) up to the formation of nascent soot clusters with diameter of up to 3.5 nm. The structure and composition of the formed soot clusters are quantified by the packing density and carbon-to-hydrogen (C/H) ratio, respectively, during nucleation and up to the formation of large nascent soot nanoparticles. Then, the nucleated incipient soot clusters are isolated from the surrounding reactive species and are allowed to coalesce with each other isothermally to investigate soot coalescence. The coalescence between incipient soot clusters of different sizes is elucidated at various process temperatures, ranging from 800 to 1800 K. The characteristic coalescence time of nascent soot is quantified by tracking the evolution of the particle surface area, for the first time. Soot clusters consisting of up to 760 atoms coalesce instantly (within 0.1 ns), especially at relatively low temperatures (i.e., 800 – 1000 K). At higher temperatures (1200 – 1600 K), incipient soot clusters are less prone to coalescence due to the larger fraction of constituent aromatic rings leading to more rigid particles. Large clusters consisting of more than 1300 atoms do not coalesce within the time scales investigated here (i.e., up to 5 ns). The employed reactive MD approach gives significant insight into fundamental soot formation and growth mechanisms, which are typically treated semi-empirically, facilitating a better understanding and more efficient control of soot in combustion processes.

Research paper thumbnail of Effect of O<sub>2</sub> concentration in ambient mixture and multiphase radiation on pollutant formation in ECN spray-A

Combustion Theory and Modelling, Feb 12, 2020

This paper is NOT THE PUBLISHED VERSION; but the author's final, peer-reviewed manuscript. The pu... more This paper is NOT THE PUBLISHED VERSION; but the author's final, peer-reviewed manuscript. The published version may be accessed by following the link in the citation below.

Research paper thumbnail of Molecular arrangement and fringe identification and analysis from molecular dynamics (MAFIA-MD): A tool for analyzing the molecular structures formed during reactive molecular dynamics simulation of hydrocarbons

Computer Physics Communications, Jul 1, 2022

Research paper thumbnail of Internal structure of incipient soot from acetylene pyrolysis obtained via molecular dynamics simulations

arXiv (Cornell University), Feb 9, 2024

A series of reactive molecular dynamics simulations is used to study the internal structure of in... more A series of reactive molecular dynamics simulations is used to study the internal structure of incipient soot particles obtained from acetylene pyrolysis. The simulations were performed using ReaxFF potential at four different temperatures. The resulting soot particles are cataloged and analyzed to obtain statistics of their mass, volume, density, C/H ratio, number of cyclic structures, and other features. A total of 3324 incipient soot particles were analyzed in this study. Based on their structural characteristics, the incipient soot particles are classified into two classes, referred to as type 1 and type 2 incipient soot particles in this work. The radial distribution of density, cyclic (5-, 6-, or 7-member rings) structures and C/H ratio inside the particles revealed a clear difference in the internal structure between type 1 and type 2 particles. These classes were further found to be well represented by the size of the particles with smaller particles in type 1 and larger particles in type 2. The radial distributions of ring structures, density, and C/H ratio indicated the presence of a dense core region in type 2 particles, whereas no clear evidence of the presence of a core was found in type 1 particles. In type 2 incipient soot particles, the boundary between the core and shell was found

Research paper thumbnail of Nano scale dynamics of bubble nucleation in confined liquid subjected to rapid cooling: Effect of solid-liquid interfacial wettability

AIP Conference Proceedings, 2017

This study focuses on the occurrence of bubble nucleation in a liquid confined in a nano scale co... more This study focuses on the occurrence of bubble nucleation in a liquid confined in a nano scale confinement and subjected to rapid cooling at one of its wall. Due to the very small size scale of the present problem, we adopt the molecular dynamics (MD) approach. The liquid (Argon) is confined within two solid (Platinum) walls. The temperature of the upper wall of the confinement is maintained at 90 K while the lower wall is being cooled rapidly to 50 K from initial equilibrium temperature of 90 K within 0.1 ns. This results in the nucleation and formation of nanobubbles in the liquid. The pattern of bubble nucleation has been studied for three different conditions of solid-liquid interfacial wettability such as hydrophilic, hydrophobic and neutral. Behavior of bubble nucleation is significantly different in the three case of solid-liquid interfacial wettability. In case of the hydrophobic confinement (weakly adsorbing), the liquid cannot achieve deeper metastability; vapor layers appear immediately on the ...

Research paper thumbnail of Effect of O\u3csub\u3e2\u3c/sub\u3e Concentration in Ambient Mixture and Multiphase Radiation on Pollutant Formation in ECN Spray-A

The present study investigates the formation and evolution of soot and NOX in a high-pressure con... more The present study investigates the formation and evolution of soot and NOX in a high-pressure constant-volume combustion chamber. This work focuses on the effect of multiphase thermal radiation and O2 dilution in ambient/exhaust gases, some- times also referred to as exhaust gas recirculation(EGR), qualitatively and quantitatively. The spray-A case (n-dodecane as fuel) from Engine Combustion Network (ECN) is used as the target condition. Two different soot modeling approaches have been considered: a semi-empirical two-equation model and a detailed method of moments with interpolative closure (MOMIC) model. A multiphase photon Monte Carlo (PMC) solver with line-by-line (LBL) spectral data is used to resolve radiative heat transfer. Results show that effect of radiation on soot is minimal in spray-A. Inclusion of radiation modeling, on the other hand, marginally reduce NO prediction. Both peak soot and NO formation increases with O2 content in the ambient gas. Oxygen content in ambien...

Research paper thumbnail of Molecular arrangement and fringe identification and analysis from molecular dynamics (MAFIA-MD): A tool for analyzing the molecular structures formed during reactive molecular dynamics simulation of hydrocarbons

Computer Physics Communications, 2022

Research paper thumbnail of kmmukut/RingDetection: RingDetection

This post-processing utility helps to identify aromatic rings in molecular dynamics trajectory fi... more This post-processing utility helps to identify aromatic rings in molecular dynamics trajectory files.

Research paper thumbnail of Effects of Radiation and EGR on Pollutant Formation in High-Pressure Constant Volume Spray Combustion

EFFECT OF RADIATION AND EGR ON POLLUTANT FORMATION IN HIGH-PRESSURE CONSTANT VOLUME SPRAY COMBUST... more EFFECT OF RADIATION AND EGR ON POLLUTANT FORMATION IN HIGH-PRESSURE CONSTANT VOLUME SPRAY COMBUSTION Khaled Mosharraf Mukut Marquette University, 2019 Soot formation is a complex process and the actual soot formation methodology is still a mystery. Numerically modeling of soot requires successful coupling of turbulence, chemistry and radiation modeling. In the present study, a comprehensive sensitivity study is conducted to see the effect of radiation and exhaust gas recirculation (EGR) on soot and NOX formation in a high pressure spray combustion scenario. The spray-A case (n-dodecane as fuel) from Engine Combustion Network (ECN) is used as the target condition. Two different soot modeling approaches have been considered: a semi-empirical two-equation model and a method of moments with interpolative closure (MOMIC). A multiphase photon Monte Carlo (PMC) solver with line-by-line (LBL) spectral database is used to resolve radiative heat transfer. Results show that, effect of radiatio...

Research paper thumbnail of The coalescence of incipient soot clusters

Carbon, 2021

Abstract Reactive molecular dynamics (MD) simulations are employed to investigate the coalescence... more Abstract Reactive molecular dynamics (MD) simulations are employed to investigate the coalescence of incipient soot clusters. Initially, one thousand acetylene molecules collide and react with each other, allowing bond breakage and new bond formation upon collision, leading to various species (e.g., linear hydrocarbons, branched polyaromatic hydrocarbons) up to the formation of nascent soot clusters with diameter of up to 3.5 nm. The structure and composition of the formed soot clusters are quantified by the packing density and carbon-to-hydrogen (C/H) ratio, respectively, during nucleation and up to the formation of large nascent soot nanoparticles. Then, the nucleated incipient soot clusters are isolated from the surrounding reactive species and are allowed to coalesce with each other isothermally to investigate soot coalescence. The coalescence between incipient soot clusters of different sizes is elucidated at various process temperatures, ranging from 800 to 1800 K. The characteristic coalescence time of nascent soot is quantified by tracking the evolution of the particle surface area, for the first time. Soot clusters consisting of up to 760 atoms coalesce instantly (within 0.1 ns), especially at relatively low temperatures (i.e., 800 – 1000 K). At higher temperatures (1200 – 1600 K), incipient soot clusters are less prone to coalescence due to the larger fraction of constituent aromatic rings leading to more rigid particles. Large clusters consisting of more than 1300 atoms do not coalesce within the time scales investigated here (i.e., up to 5 ns). The employed reactive MD approach gives significant insight into fundamental soot formation and growth mechanisms, which are typically treated semi-empirically, facilitating a better understanding and more efficient control of soot in combustion processes.

Research paper thumbnail of Atomistic modelling of thin film argon evaporation over different solid surfaces at different wetting conditions

Micro & Nano Letters, 2018

In the present study, non-equilibrium molecular dynamics (MD) simulations have been performed to ... more In the present study, non-equilibrium molecular dynamics (MD) simulations have been performed to reveal the effect of solid-liquid interfacial wettability on the evaporation characteristics of thin liquid argon film placed over the flat solid surface. The atomistic model considered herein comprises of a three-phase simulation domain having a solid wall over which liquid argon and argon vapour co-exist. Initially, the system is thermally equilibrated at 90 K for a while after which rapid increase in the solid wall temperature induces a phase change process, i.e. evaporation. Both hydrophilic and hydrophobic wetting conditions of the solid surface have been considered at an evaporation temperature of 130 K for three different surface materials such as platinum, silver, and aluminium. The simulation results show that both the surface wettability and surface material have a significant role in phase transition phenomena of thin liquid film, particularly the surface wettability for the present system configuration. The thermal transport phenomena between the wall and liquid thin film have been studied thoroughly and discussed in terms of wall heat flux, evaporative mass flux, upper bound of maximum possible heat flux etc. The results obtained in the present MD simulation study are compared with the macroscopic predictions based on classical thermodynamics. Interestingly, a very good agreement has been found indicating that macroscopic thermodynamics approach can predict the characteristic of phase change phenomena of nanoscale thin liquid film.

Research paper thumbnail of A molecular dynamics study on thin film liquid boiling characteristics under rapid linear boundary heating: Effect of liquid film thickness

AIP Conference Proceedings, 2017

This study is a molecular dynamics investigation of phase change phenomena i.e. boiling of thin l... more This study is a molecular dynamics investigation of phase change phenomena i.e. boiling of thin liquid films subjected to rapid linear heating at the boundary. The purpose of this study is to understand the phase change heat transfer phenomena at nano scale level. In the simulation, a thin film of liquid argon over a platinum surface has been considered. The simulation domain herein is a three-phase system consisting of liquid and vapor argon atoms placed over a platinum wall. Initially the whole system is brought to an equilibrium state at 90 K and then the temperature of the bottom wall is increased to a higher temperature (250K) within a finite time interval. Four different liquid argon film thicknesses have been considered (3 nm, 4 nm, 5 nm and 6 nm) in this study. The boundary heating rate (40×109 K/s) is kept constant in all these cases. Variation in system temperature, pressure, net evaporation number, spatial number density of the argon region with time for different film thickness have been demon...

Research paper thumbnail of Phase Change Characteristics of Ultra-Thin Liquid Argon Film over different Flat Substrates at High Wall Superheat for Hydrophilic/Hydrophobic Wetting Condition: A Non-Equilibrium Molecular Dynamics Study

Journal of Chemical Engineering, 2017

Non-equilibrium molecular dynamics simulations have been conducted to understand the effect of so... more Non-equilibrium molecular dynamics simulations have been conducted to understand the effect of solid-liquid interfacial wettability and surface material on the phase change phenomena of the thin liquid argon film placed over flat substrate at high wall superheat. The molecular system consists of a three phase simulation domain involving solid wall, liquid argon and argon vapor. After the system is thermally equilibrated at 90K and kept in equilibrium for a while, a high wall superheat (250K that is far above the critical temperature of argon) is induced at the liquid boundary so that the liquid undergoes ultrafast heating. Both hydrophilic and hydrophobic surfaces were considered in the present study in order to observe the effect of surface wettability on phase change characteristics for three different solid substrate materials namely, Platinum (Pt), Silver (Ag) and Aluminium (Al). Results obtained in the present study are discussed in terms of transient atomic distribution inside...

Research paper thumbnail of Thermal transport during thin-film argon evaporation over nanostructured platinum surface: A molecular dynamics study

Proceedings of the Institution of Mechanical Engineers, Part N: Journal of Nanomaterials, Nanoengineering and Nanosystems, 2018

Investigation of thermal transport characteristics of thin-film liquid evaporation over nanostruc... more Investigation of thermal transport characteristics of thin-film liquid evaporation over nanostructured surface has been conducted using molecular dynamics simulation with particular importance on the effects of the nanostructure configuration for different wall–fluid interaction strengths. The nanostructured surface considered herein comprises wall-through rectangular nanoposts placed over a flat wall. Both the substrate and the nanostructure are of platinum while argon is used as the evaporating liquid. Two different wall–fluid interaction strengths have been considered that essentially emulate both hydrophilic and hydrophobic wetting conditions for three different nanostructure configurations. The argon–platinum molecular system is first equilibrated at 90 K and then followed by a sudden increase in the wall temperature at 130 K that induces evaporation of argon laid over it. Comparative effectiveness of heat and mass transfer for different surface wetting conditions has been stud...

Research paper thumbnail of Effect of O2 concentration in ambient mixture and multiphase radiation on pollutant formation in ECN spray-A

Combustion Theory and Modelling

This paper is NOT THE PUBLISHED VERSION; but the author's final, peer-reviewed manuscript. The pu... more This paper is NOT THE PUBLISHED VERSION; but the author's final, peer-reviewed manuscript. The published version may be accessed by following the link in the citation below.

Research paper thumbnail of Physical, chemical and morphological evolution of incipient soot obtained from molecular dynamics simulation of acetylene pyrolysis

arXiv (Cornell University), Feb 9, 2024

Incipient soot particles obtained from a series of reactive molecular dynamics simulations were s... more Incipient soot particles obtained from a series of reactive molecular dynamics simulations were studied to understand the evolution of physical, chemical, and morphological properties of incipient soot. Reactive molecular dynamics simulations of acetylene pyrolysis were performed using ReaxFF potential at 1350, 1500, 1650, and 1800 K. A total of 3324 incipient soot particles were extracted from the simulations at various stages of development. Features such as the number of carbon and hydrogen atoms, number of ring structures, mass, C/H ratio, radius of gyration, surface area, volume, atomic fractal dimension, and density were calculated for each particle. The calculated values of density and C/H ratio matched well with experimental values reported in the literature. Based on the calculated features, the particles were classified in two types: type 1 and type 2 particles. It was found that type 1 particles show significant morphological evolution while type 2 particles undergo chemical restructuring without any significant morphological change. The particle volume was found to be well-correlated with the number of carbon

Research paper thumbnail of The coalescence of incipient soot clusters

Carbon, Aug 1, 2021

Abstract Reactive molecular dynamics (MD) simulations are employed to investigate the coalescence... more Abstract Reactive molecular dynamics (MD) simulations are employed to investigate the coalescence of incipient soot clusters. Initially, one thousand acetylene molecules collide and react with each other, allowing bond breakage and new bond formation upon collision, leading to various species (e.g., linear hydrocarbons, branched polyaromatic hydrocarbons) up to the formation of nascent soot clusters with diameter of up to 3.5 nm. The structure and composition of the formed soot clusters are quantified by the packing density and carbon-to-hydrogen (C/H) ratio, respectively, during nucleation and up to the formation of large nascent soot nanoparticles. Then, the nucleated incipient soot clusters are isolated from the surrounding reactive species and are allowed to coalesce with each other isothermally to investigate soot coalescence. The coalescence between incipient soot clusters of different sizes is elucidated at various process temperatures, ranging from 800 to 1800 K. The characteristic coalescence time of nascent soot is quantified by tracking the evolution of the particle surface area, for the first time. Soot clusters consisting of up to 760 atoms coalesce instantly (within 0.1 ns), especially at relatively low temperatures (i.e., 800 – 1000 K). At higher temperatures (1200 – 1600 K), incipient soot clusters are less prone to coalescence due to the larger fraction of constituent aromatic rings leading to more rigid particles. Large clusters consisting of more than 1300 atoms do not coalesce within the time scales investigated here (i.e., up to 5 ns). The employed reactive MD approach gives significant insight into fundamental soot formation and growth mechanisms, which are typically treated semi-empirically, facilitating a better understanding and more efficient control of soot in combustion processes.

Research paper thumbnail of Effect of O<sub>2</sub> concentration in ambient mixture and multiphase radiation on pollutant formation in ECN spray-A

Combustion Theory and Modelling, Feb 12, 2020

This paper is NOT THE PUBLISHED VERSION; but the author's final, peer-reviewed manuscript. The pu... more This paper is NOT THE PUBLISHED VERSION; but the author's final, peer-reviewed manuscript. The published version may be accessed by following the link in the citation below.

Research paper thumbnail of Molecular arrangement and fringe identification and analysis from molecular dynamics (MAFIA-MD): A tool for analyzing the molecular structures formed during reactive molecular dynamics simulation of hydrocarbons

Computer Physics Communications, Jul 1, 2022

Research paper thumbnail of Internal structure of incipient soot from acetylene pyrolysis obtained via molecular dynamics simulations

arXiv (Cornell University), Feb 9, 2024

A series of reactive molecular dynamics simulations is used to study the internal structure of in... more A series of reactive molecular dynamics simulations is used to study the internal structure of incipient soot particles obtained from acetylene pyrolysis. The simulations were performed using ReaxFF potential at four different temperatures. The resulting soot particles are cataloged and analyzed to obtain statistics of their mass, volume, density, C/H ratio, number of cyclic structures, and other features. A total of 3324 incipient soot particles were analyzed in this study. Based on their structural characteristics, the incipient soot particles are classified into two classes, referred to as type 1 and type 2 incipient soot particles in this work. The radial distribution of density, cyclic (5-, 6-, or 7-member rings) structures and C/H ratio inside the particles revealed a clear difference in the internal structure between type 1 and type 2 particles. These classes were further found to be well represented by the size of the particles with smaller particles in type 1 and larger particles in type 2. The radial distributions of ring structures, density, and C/H ratio indicated the presence of a dense core region in type 2 particles, whereas no clear evidence of the presence of a core was found in type 1 particles. In type 2 incipient soot particles, the boundary between the core and shell was found

Research paper thumbnail of Nano scale dynamics of bubble nucleation in confined liquid subjected to rapid cooling: Effect of solid-liquid interfacial wettability

AIP Conference Proceedings, 2017

This study focuses on the occurrence of bubble nucleation in a liquid confined in a nano scale co... more This study focuses on the occurrence of bubble nucleation in a liquid confined in a nano scale confinement and subjected to rapid cooling at one of its wall. Due to the very small size scale of the present problem, we adopt the molecular dynamics (MD) approach. The liquid (Argon) is confined within two solid (Platinum) walls. The temperature of the upper wall of the confinement is maintained at 90 K while the lower wall is being cooled rapidly to 50 K from initial equilibrium temperature of 90 K within 0.1 ns. This results in the nucleation and formation of nanobubbles in the liquid. The pattern of bubble nucleation has been studied for three different conditions of solid-liquid interfacial wettability such as hydrophilic, hydrophobic and neutral. Behavior of bubble nucleation is significantly different in the three case of solid-liquid interfacial wettability. In case of the hydrophobic confinement (weakly adsorbing), the liquid cannot achieve deeper metastability; vapor layers appear immediately on the ...

Research paper thumbnail of Effect of O\u3csub\u3e2\u3c/sub\u3e Concentration in Ambient Mixture and Multiphase Radiation on Pollutant Formation in ECN Spray-A

The present study investigates the formation and evolution of soot and NOX in a high-pressure con... more The present study investigates the formation and evolution of soot and NOX in a high-pressure constant-volume combustion chamber. This work focuses on the effect of multiphase thermal radiation and O2 dilution in ambient/exhaust gases, some- times also referred to as exhaust gas recirculation(EGR), qualitatively and quantitatively. The spray-A case (n-dodecane as fuel) from Engine Combustion Network (ECN) is used as the target condition. Two different soot modeling approaches have been considered: a semi-empirical two-equation model and a detailed method of moments with interpolative closure (MOMIC) model. A multiphase photon Monte Carlo (PMC) solver with line-by-line (LBL) spectral data is used to resolve radiative heat transfer. Results show that effect of radiation on soot is minimal in spray-A. Inclusion of radiation modeling, on the other hand, marginally reduce NO prediction. Both peak soot and NO formation increases with O2 content in the ambient gas. Oxygen content in ambien...

Research paper thumbnail of Molecular arrangement and fringe identification and analysis from molecular dynamics (MAFIA-MD): A tool for analyzing the molecular structures formed during reactive molecular dynamics simulation of hydrocarbons

Computer Physics Communications, 2022

Research paper thumbnail of kmmukut/RingDetection: RingDetection

This post-processing utility helps to identify aromatic rings in molecular dynamics trajectory fi... more This post-processing utility helps to identify aromatic rings in molecular dynamics trajectory files.

Research paper thumbnail of Effects of Radiation and EGR on Pollutant Formation in High-Pressure Constant Volume Spray Combustion

EFFECT OF RADIATION AND EGR ON POLLUTANT FORMATION IN HIGH-PRESSURE CONSTANT VOLUME SPRAY COMBUST... more EFFECT OF RADIATION AND EGR ON POLLUTANT FORMATION IN HIGH-PRESSURE CONSTANT VOLUME SPRAY COMBUSTION Khaled Mosharraf Mukut Marquette University, 2019 Soot formation is a complex process and the actual soot formation methodology is still a mystery. Numerically modeling of soot requires successful coupling of turbulence, chemistry and radiation modeling. In the present study, a comprehensive sensitivity study is conducted to see the effect of radiation and exhaust gas recirculation (EGR) on soot and NOX formation in a high pressure spray combustion scenario. The spray-A case (n-dodecane as fuel) from Engine Combustion Network (ECN) is used as the target condition. Two different soot modeling approaches have been considered: a semi-empirical two-equation model and a method of moments with interpolative closure (MOMIC). A multiphase photon Monte Carlo (PMC) solver with line-by-line (LBL) spectral database is used to resolve radiative heat transfer. Results show that, effect of radiatio...

Research paper thumbnail of The coalescence of incipient soot clusters

Carbon, 2021

Abstract Reactive molecular dynamics (MD) simulations are employed to investigate the coalescence... more Abstract Reactive molecular dynamics (MD) simulations are employed to investigate the coalescence of incipient soot clusters. Initially, one thousand acetylene molecules collide and react with each other, allowing bond breakage and new bond formation upon collision, leading to various species (e.g., linear hydrocarbons, branched polyaromatic hydrocarbons) up to the formation of nascent soot clusters with diameter of up to 3.5 nm. The structure and composition of the formed soot clusters are quantified by the packing density and carbon-to-hydrogen (C/H) ratio, respectively, during nucleation and up to the formation of large nascent soot nanoparticles. Then, the nucleated incipient soot clusters are isolated from the surrounding reactive species and are allowed to coalesce with each other isothermally to investigate soot coalescence. The coalescence between incipient soot clusters of different sizes is elucidated at various process temperatures, ranging from 800 to 1800 K. The characteristic coalescence time of nascent soot is quantified by tracking the evolution of the particle surface area, for the first time. Soot clusters consisting of up to 760 atoms coalesce instantly (within 0.1 ns), especially at relatively low temperatures (i.e., 800 – 1000 K). At higher temperatures (1200 – 1600 K), incipient soot clusters are less prone to coalescence due to the larger fraction of constituent aromatic rings leading to more rigid particles. Large clusters consisting of more than 1300 atoms do not coalesce within the time scales investigated here (i.e., up to 5 ns). The employed reactive MD approach gives significant insight into fundamental soot formation and growth mechanisms, which are typically treated semi-empirically, facilitating a better understanding and more efficient control of soot in combustion processes.

Research paper thumbnail of Atomistic modelling of thin film argon evaporation over different solid surfaces at different wetting conditions

Micro & Nano Letters, 2018

In the present study, non-equilibrium molecular dynamics (MD) simulations have been performed to ... more In the present study, non-equilibrium molecular dynamics (MD) simulations have been performed to reveal the effect of solid-liquid interfacial wettability on the evaporation characteristics of thin liquid argon film placed over the flat solid surface. The atomistic model considered herein comprises of a three-phase simulation domain having a solid wall over which liquid argon and argon vapour co-exist. Initially, the system is thermally equilibrated at 90 K for a while after which rapid increase in the solid wall temperature induces a phase change process, i.e. evaporation. Both hydrophilic and hydrophobic wetting conditions of the solid surface have been considered at an evaporation temperature of 130 K for three different surface materials such as platinum, silver, and aluminium. The simulation results show that both the surface wettability and surface material have a significant role in phase transition phenomena of thin liquid film, particularly the surface wettability for the present system configuration. The thermal transport phenomena between the wall and liquid thin film have been studied thoroughly and discussed in terms of wall heat flux, evaporative mass flux, upper bound of maximum possible heat flux etc. The results obtained in the present MD simulation study are compared with the macroscopic predictions based on classical thermodynamics. Interestingly, a very good agreement has been found indicating that macroscopic thermodynamics approach can predict the characteristic of phase change phenomena of nanoscale thin liquid film.

Research paper thumbnail of A molecular dynamics study on thin film liquid boiling characteristics under rapid linear boundary heating: Effect of liquid film thickness

AIP Conference Proceedings, 2017

This study is a molecular dynamics investigation of phase change phenomena i.e. boiling of thin l... more This study is a molecular dynamics investigation of phase change phenomena i.e. boiling of thin liquid films subjected to rapid linear heating at the boundary. The purpose of this study is to understand the phase change heat transfer phenomena at nano scale level. In the simulation, a thin film of liquid argon over a platinum surface has been considered. The simulation domain herein is a three-phase system consisting of liquid and vapor argon atoms placed over a platinum wall. Initially the whole system is brought to an equilibrium state at 90 K and then the temperature of the bottom wall is increased to a higher temperature (250K) within a finite time interval. Four different liquid argon film thicknesses have been considered (3 nm, 4 nm, 5 nm and 6 nm) in this study. The boundary heating rate (40×109 K/s) is kept constant in all these cases. Variation in system temperature, pressure, net evaporation number, spatial number density of the argon region with time for different film thickness have been demon...

Research paper thumbnail of Phase Change Characteristics of Ultra-Thin Liquid Argon Film over different Flat Substrates at High Wall Superheat for Hydrophilic/Hydrophobic Wetting Condition: A Non-Equilibrium Molecular Dynamics Study

Journal of Chemical Engineering, 2017

Non-equilibrium molecular dynamics simulations have been conducted to understand the effect of so... more Non-equilibrium molecular dynamics simulations have been conducted to understand the effect of solid-liquid interfacial wettability and surface material on the phase change phenomena of the thin liquid argon film placed over flat substrate at high wall superheat. The molecular system consists of a three phase simulation domain involving solid wall, liquid argon and argon vapor. After the system is thermally equilibrated at 90K and kept in equilibrium for a while, a high wall superheat (250K that is far above the critical temperature of argon) is induced at the liquid boundary so that the liquid undergoes ultrafast heating. Both hydrophilic and hydrophobic surfaces were considered in the present study in order to observe the effect of surface wettability on phase change characteristics for three different solid substrate materials namely, Platinum (Pt), Silver (Ag) and Aluminium (Al). Results obtained in the present study are discussed in terms of transient atomic distribution inside...

Research paper thumbnail of Thermal transport during thin-film argon evaporation over nanostructured platinum surface: A molecular dynamics study

Proceedings of the Institution of Mechanical Engineers, Part N: Journal of Nanomaterials, Nanoengineering and Nanosystems, 2018

Investigation of thermal transport characteristics of thin-film liquid evaporation over nanostruc... more Investigation of thermal transport characteristics of thin-film liquid evaporation over nanostructured surface has been conducted using molecular dynamics simulation with particular importance on the effects of the nanostructure configuration for different wall–fluid interaction strengths. The nanostructured surface considered herein comprises wall-through rectangular nanoposts placed over a flat wall. Both the substrate and the nanostructure are of platinum while argon is used as the evaporating liquid. Two different wall–fluid interaction strengths have been considered that essentially emulate both hydrophilic and hydrophobic wetting conditions for three different nanostructure configurations. The argon–platinum molecular system is first equilibrated at 90 K and then followed by a sudden increase in the wall temperature at 130 K that induces evaporation of argon laid over it. Comparative effectiveness of heat and mass transfer for different surface wetting conditions has been stud...

Research paper thumbnail of Effect of O2 concentration in ambient mixture and multiphase radiation on pollutant formation in ECN spray-A

Combustion Theory and Modelling

This paper is NOT THE PUBLISHED VERSION; but the author's final, peer-reviewed manuscript. The pu... more This paper is NOT THE PUBLISHED VERSION; but the author's final, peer-reviewed manuscript. The published version may be accessed by following the link in the citation below.