Search

Your search keyword '"Ahmadi, G."' showing total 787 results
Start Over Author "Ahmadi, G."
787 results on '"Ahmadi, G."'

4. Host-to-Host Airborne Transmission As a Multiphase Flow Problem For Science-Based Social Distance Guidelines

Author

Balachandar, S., Zaleski, S., Soldati, A., Ahmadi, G., and Bourouiba, L.

Subjects
Physics - Fluid Dynamics, Physics - Physics and Society
Abstract

COVID-19 pandemic has strikingly demonstrated how important it is to develop fundamental knowledge related to generation, transport and inhalation of pathogen-laden droplets and their subsequent possible fate as airborne particles, or aerosols, in the context of human to human transmission. It is also increasingly clear that airborne transmission is an important contributor to rapid spreading of the disease. In this paper, we discuss the processes of droplet generation by exhalation, their potential transformation into airborne particles by evaporation, transport over long distances by the exhaled puff and by ambient air turbulence, and final inhalation by the receiving host as interconnected multiphase flow processes. A simple model for the time evolution of droplet/aerosol concentration is presented based on a theoretical analysis of the relevant physical processes. The modeling framework along with detailed experiments and simulations can be used to study a wide variety of scenarios involving breathing, talking, coughing and sneezing and in a number of environmental conditions, as humid or dry atmosphere, confined or open environment. Although a number of questions remain open on the physics of evaporation and coupling with persistence of the virus, it is clear that with a more reliable understanding of the underlying flow physics of virus transmission one can set the foundation for an improved methodology in designing case-specific social distancing and infection control guidelines., Comment: 14 figures and 40 pages

Published
2020

11. Designing the sinc neural networks to solve the fractional optimal control problem.

Author

Dastjerdi, R. Heydari and Ahmadi, G.

Subjects
ORDINARY differential equations, PROBLEM solving, APPROXIMATION theory, ERROR functions, COMPUTER simulation
Abstract

Sinc numerical methods are essential approaches for solving nonlinear problems. In this work, based on this method, the sinc neural networks (SNNs) are designed and applied to solve the fractional optimal control problem (FOCP) in the sense of the Riemann–Liouville (RL) derivative. To solve the FOCP, we first approximate the RL derivative using Grunwald–Letnikov ofaators. Then, according to Pontryagin's minimum principle for FOCP and using an error function, we construct an unconstrained minimization problem. We approximate the solution of the ordinary differential equation obtained from the Hamiltonian condition using the SNN. Simulation results show the efficiencies of the proposed approach. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

12. Optimization of Ventilation Register Locations for Reducing Suspended Particle Concentration Using the Taguchi Method.

Author

Sajjadi, H., Nabavi, S. N., Ahmadi, G., Delouei, A. Amiri, and Naeimi, H.

Subjects
LATTICE Boltzmann methods, TAGUCHI methods, AIR conditioning, INFECTIOUS disease transmission, AIR flow
Abstract

In the present study, the Multi-Relaxation Time Lattice Boltzmann method (MRT-LBM) was employed to solve the airflow inside a scaled room model with dimensions of 0.914x0.457x0.305 m. This room model is considered a representative space with a 1:10 scale to an actual room. The selected room is equipped with a ventilation system. For optimizing the inlet and outlet locations of the airflow, 32 different positions in terms of length, width, and height for the inlet and 4 positions for the outlet were considered. The Taguchi method was utilized for optimizing the inlet and outlet locations, reducing the required number of experiments from 128 to 16. To assess the number of suspended particles, 86400 particles with a size of 1µm were injected into the room. Then, the particle behaviors were examined for a total duration of 60 seconds. The obtained results indicate that the location of the air conditioning system significantly influences the concentration of airborne particles responsible for disease transmission. Utilizing the Taguchi optimization method, optimal positions for the inlet and outlet air were determined to minimize the number of suspended particles in the room (the best position) and maximize it (the worst position). [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

49. Performance Analysis of a Gas Cyclone with a Dustbin Inverted Hybrid Solid Cone

Author

Dehdarinejad, E., Parvaz, F., Hosseini, S. H., Ahmadi, G., and Elsayed, K.

Abstract

This study uses the CFD technique to investigate the influence of a twisted inverted hybrid solid cone (TIHSC) placed at the gas cyclone dustbin on the separator performance. This new design improves the stability and reduces the length of the vortex finder, resulting in a stronger swirl in the cyclone with a higher tangential velocity. The study showed that an increase in the height of the TIHSC increases the maximum tangential velocity up to 2.9 times the inlet velocity. Overall, using TIHSC leads to a significant increase in particle separation efficiency compared to the conventional cyclone. In addition, with an increase in the height of TIHSC, the pressure drop significantly decreases while the separation efficiency increases. For the optimized model, the particle cut size improves from 0.97 to 0.85 µm at 50% separation and from 6.2 to 4.7 µm at 100% separation, while the pressure drop is reduced by 12.7%. Copyright © 2023 American Association for Aerosol Research

Published
2023
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results