About

Welcome to my website. I have completed my Ph.D. in Mechanical Engineering at the University of Maryland (UMD), where I served as a Graduate Research Assistant with Prof. Arnaud Trouvé. My Ph.D. research topic was Development of a Lagrangian-Eulerian Modeling Framework to Describe Thermal Degradation of Porous Fuel Particles in Simulations of Wildland Fire Behavior at Flame Scale.

My academic journey includes earning a B.Sc. and M.Sc. in Aerospace Engineering from Cairo University. Prior to my doctoral studies, I gained valuable experience in computational modeling of thermal-fluid systems at Optumatics in Cairo, Egypt. I have also worked previously at Canon Nanotechnologies in Austin, TX as an Engineering Intern, at the American University of the Middle East as a Laboratory Instructor, and at Cairo University as Teacing Assistant.

My interests include: Fire, Thermal management, Propulsion, Aerodynamics, Turbulence, CFD, software development, and High-Performance Computing.

Research Work

Solid biomass thermo-chemical degradation and flame propagation

This research aims to create an advanced physics-based computational tool for detailed modeling of the interaction between solid-phase and gas-phase processes in wildland fires. The focus is on resolving flame and vegetation-scale processes, including vapor formation from porous biomass, combustion with ambient air, turbulent flow generation, and thermal feedback to solid biomass. The developed modeling capability, PBRFoam, utilizes OpenFOAM and an in-house Lagrangian Particle Burning Rate (PBR) model for comprehensive simulation of fire spread in vegetation fuel beds, considering thermal degradation in both flaming and smoldering combustion.

Unstable flame structure and gas-to-liquid thermal feedback in pool fires

Conducting Fine-grained Large Eddy Simulations (LES) on a standard 30-cm methanol pool fire setup, we assess the accuracy of existing fire models in predicting flame structure and heat transfer rates to the liquid fuel surface. The emphasis is on grid design and spatial resolution, with varying attention given to LES model formulations, particularly radiation treatment. The simulations mirror experimental observations, capturing flame instability and vortex ring formation. Results indicate that, with a sufficiently fine grid, current fire models can predict gas-to-fuel thermal feedback, though simulations tend to overestimate feedback intensity by 25%.

Simulations of thermo-chemical degradation of solid biomass particles under oscillatory heating conditions

This study explores the burning process of biomass fuel particles under oscillatory heat flux conditions resembling flapping flames or fluctuations in irradiation over natural vegetation. Numerical simulations reveal a quasi-linear response to fluctuating irradiation or local gas temperature, suggesting negligible effects of oscillations. However, a non-linear response occurs with unsteady convective heating, resulting in increased heat transfer, higher temperatures, elevated fuel mass loss rates, and shorter burnout times.

Simulations of hypersonic flow at Mach 8 around a sphere cone using a morphing continuum approach

An openFoam CFD library is utilized to create a non-equilibrium flow solver, extending a set of fluid governing equations known as Morphing Continuum Theory (MCT). Initially introduced by A. Eringen for micropolar continuum fluids, MCT was later derived by J. Chen and colleagues from statistical mechanics and adopted for turbulence and hypersonic simulations.

Boltzmann-Curtiss description for flows under translational non-equilibrium

The Boltzmann–Curtiss formulation, known as Morphing Continuum Theory (MCT), describes gases with both rotational and translational degrees-of-freedom. Its first-order solution reveals a stress tensor influenced by particle density, temperature, and total relaxation time. Employing a new bulk viscosity model improves shock structure and temperature profiles in numerical simulations, showing significant enhancements over NS equations under nonequilibrium conditions compared to experimental measurements and DSMC method.

Transonic axial flow compressors with tandem rotor blades

Tandem rotor blades offer the potential to enhance transonic axial flow compressor performance, achieving a higher pressure ratio per stage and reducing the overall compressor weight. Numerical investigations of an optimal tandem rotor design, based on the inflow characteristics of the reference transonic rotor 'NASA Rotor 37,' demonstrate significant improvements in flow turning and diffusion without flow separation. The tandem design exhibits a 17% increase in total pressure ratio and a 2% increase in rotor adiabatic efficiency at the design point compared to the baseline rotor.

Analysis of hypersonic flows using Ideal Dissociating Gas (IDG) model

Ideal Dissociating Gas (IDG) model is adopted in a shock-tunnel problem to analyze the flow relaxation behind shocks, the non-equilibrium expansion in the nozzle and the flow behind an oblique shock.

Incompressible Navier-Stokes Solver and Iterative Methods

This study compares the convergence of different classical algorithms, such as Jacobi, Gauss-Seidel (GS), Alternating Direction Implicit (ADI), Successive Over-Relaxation (SOR) and its line variants, and V cycle Multi Grid, using a dveloped Fortran-90 code running on a single processor. More details can be found here and here.

Taylor-Green vortex at different convective schemes

Dissipative error of different convective schemes available in OpenFoam is examined in a DNS simulation of the classical Taylor-Green vortex problem. The plots compare the predicted evolution of the kinetic energy and enstrophy with the exact solution.

Decay of homogeneous isotropic turbulence in LES

The classical isotropic box turbulence problem is used to examine different LES subgrid-scale models. The plots show the predicted grid resolved kinetic energy (GS) and the total kinetic energy (GS+SGS) and the data by Comte-Bellot and Corrsin (CBC). The results show that the Dynamic K-equation model over predicts the SGS kinetic energy.

Education

University of Maryland
PhD in Mechanical Engineering, 2023
Advisor: Prof. Arnaud Trouvé

Cairo University
MSc in Aerospace Engineering, 2015
BSc in Aerospace Engineering, 2011

Publications

Book Chapters

1. Salman Verma, Mohamed Mohsen Ahmed, , and Arnaud Trouvé (2022). The Structure of Line Fires at Flame Scale. In K. Speer & S. Goodrick (Eds.), "Wildland Fire Dynamics" (pp. 35-62). Cambridge: Cambridge University Press.

Peer-reviewed Journal Articles

1. Mohamed Mohsen Ahmed, , Arnaud Trouvé, Jason Forthofer, and Mark Finney. Simulations of Flaming Combustion and Flaming-to-Smoldering Transition in Wildland Fire Spread at Flame Scale. Combustion and Flame 262 (2024) 113370.

2. Mohamed Moshen Ahmed, and Arnaud Trouvé. Large eddy simulation of the unstable flame structure and gas-to-liquid thermal feedback in a medium-scale methanol pool fire. Combustion and Flame 225 (2021) 237-254.

3. Rani Taher, Mohamed Mohsen Ahmed Ahmed , Zoubida Haddad, and Cherifa Abid. Poiseuille-Rayleigh-Bénard mixed convection flow in a channel: Heat transfer and fluid flow patterns. International Journal of Heat and Mass Transfer 180 (2021) 121745.

4. Mohamed Mohsen Ahmed, and Arnaud Trouvé. Simulations of the unsteady response of biomass burning particles exposed to oscillatory heat flux conditions. Fire Safety Journal 120 (2021) 103059.

5. Mohamed Mohsen Ahmed, Mohamed Ibrahim Cheikh, and James Chen. Boltzmann–Curtiss Description for Flows Under Translational Nonequilibrium. Journal of Fluids Engineering 142 (2020).

6. Mohamed Mohsen, Farouk Owis, and Ali Hashim. The impact of tandem rotor blades on the performance of transonic axial compressors. Aerospace Science and Technology 67 (2017) 237-248.

Conferences Proceedings

1. Mohamed Mohsen Ahmed, Arnaud Trouvé, Jason Forthofer, and Mark Finney. Simulation of Fire Spread over Discrete and Loosely Packed Cardboard Fuel Beds. In 13th U.S. National Combustion Meeting (2023).

2. Mohamed Mohsen Ahmed, Arnaud Trouvé, Jason Forthofer, and Mark Finney. Large eddy simulations of the structure of spreading line fires at flame scale. In Advances in Forest Fire Research" (2022).

3. Mohamed Mohsen Ahmed , and James Chen. Verification and Validation of a Morphing Continuum Approach to Hypersonic Flow Simulations. In AIAA Scitech 2019 Forum (2019).

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