The present study investigates aerosol transport and surface deposition in a realistic classroom environment using computational fluid-particle dynamics simulations. Effects of particle size, aerosol source location, glass barriers, and windows are explored. While aerosol transport in air exhibits some stochasticity, it is found that a significant fraction (24%–50%) of particles smaller than 15 µ m exit the system within 15 min through the air conditioning system. Particles larger than 20 µ m almost entirely deposit on the ground, desks, and nearby surfaces in the room. Source location strongly influences the trajectory and deposition distribution of the exhaled aerosol particles and affects the effectiveness of mitigation measures such as glass barriers. Glass barriers are found to reduce the aerosol transmission of 1 µ m particles from the source individual to others separated by at least 2.4 m by ∼92%. By opening windows, the particle exit fraction can be increased by ∼38% compared to the case with closed windows and reduces aerosol deposition on people in the room. On average, ∼69% of 1 µ m particles exit the system when the windows are open.

Identifying economically viable intervention measures to reduce COVID-19 transmission on aircraft is of critical importance especially as new SARS-CoV2 variants emerge. Computational fluid-particle dynamic simulations are employed to investigate aerosol transmission and intervention measures on a Boeing 737 cabin zone. The present study compares aerosol transmission in three models: (a) a model at full passenger capacity (60 passengers), (b) a model at reduced capacity (40 passengers), and (c) a model at full capacity with sneeze guards/shields between passengers. Lagrangian simulations are used to model aerosol transport using particle sizes in the 1–50 μ m range, which spans aerosols emitted during breathing, speech, and coughing. Sneeze shields placed between passengers redirect the local air flow and transfer part of the lateral momentum of the air to longitudinal momentum. This mechanism is exploited to direct more particles to the back of the seats in front of the index patient (aerosol source) and reduce lateral transfer of aerosol particles to other passengers. It is demonstrated that using sneeze shields on full capacity flights can reduce aerosol transmission to levels below that of reduced capacity flights without sneeze shields.

No abstract

This paper presents a steady state one-dimensional two-fluid model for gas-solid two-phase flow in a vertical riser. The model is solved using conservative variable approach for the gas phase, and fourth order RungeKutta method is used for the solid phase. The model predictions for pressure drop are compared with available experimental data and with Eulerian-Lagrangian predictions, and a good agreement is obtained. The results indicate that the pressure drop increases as the solid mass flow rate, particle size, and particles density increase. In addition, the model predictions for minimum pressure drop velocity are compared with experimental data from literature and the mean percentage error. MPE for minimum pressure drop velocity is -9.89%. It is found that the minimum pressure drop velocity increases as the solid mass flow, particle size and particle density increase, and decreases as the system total pressure increases.

In the present work, the wake behavior of wind turbines operating under thermallystratified atmospheric boundary layer (ABL) is numerically investigated. The steady state three dimensional Reynolds-Averaged Navier-Stokes (RANS) equations, combined with actuator disk approach, are used in the simulation. The standard ݇-ߝ turbulence model as well as two modified models namely Crespo model and El kasmi model are adopted. Two different methods are used and compared, to represent the atmospheric stratification conditions. In the first method, the energy equation is considered along with mass, momentum, and turbulence model equations. The stratification in the second method is modeled by means of an additional buoyancy production or dissipation term, which is added to the equation of the turbulent kinetic energy, instead of solving the energy equation. The results obtained from both methods show reasonable agreement with the experimental data available from the literature.

This paper calculates the stress function constants to determine and analyse the stress field of a beam with an elliptical cross-section under transverse loading. This was performed using linear elasticity principles. The Beltrami-Michell compatibility equations were used to derive the formulas used to calculate these parameters in the beam with the elliptical cross-section. This paper uses dimensionless analysis to comprehend the effect of each variable in the problem. The loading was applied at the centre of the right-end face of the elliptical beam. This loading configuration is the same as an existing linear elasticity problem; however, that problem models a cylindrical beam instead of an elliptical one. Thus, the existing parameters from the cylindrical model were used to verify the formulas, calculated in this paper, for the elliptical beam.

No abstract

This study introduces a numerical investigation on the impact of different inflow atmospheric conditions on the wind turbine wakes. The effects of the inflow turbulence intensity and wind speed under thermally-stratified atmospheric boundary layer (ABL) are presented and discussed. The steady state three dimensional Reynolds-Averaged Navier-Stokes (RANS) equations are solved in the simulation, along with the Actuator Disk Method (ADM) for the turbine rotor modeling. A modified-model, namely El Kasmi model, is adopted for the turbulence modulation. Further, an additional source term is added to the turbulence equations, to artificially represent the buoyancy generated turbulence, without the need to solve the energy equation. It is found that, there is a considerable effect of the different atmospheric flow properties on the wake flow behavior. Particularly, as the turbulence intensity increases, the wake recovers faster and hence, the wake deficit decreases and the available wind power in the wake region increases. Further, the wake deficits values immediately downstream the turbine are higher for the lower inflow wind speeds.