Reducing NOx Emissions of Cargo Handling Equipment (CHE) with Humid Air Systems

The authors designed and tested a humid air system (HAS) for reducing NOx emissions of an LPG-powered forklift. The HAS uses distilled water and heat from the exhaust to generate steam that is injected into the intake air of the engine to increase humidity and thus achieve NOx reduction. Field tests with HAS have shown 2.2 ppm of NOx reduction with each percent increase in humidity of the intake air. A provisional patent based on the developed system has been filed

Large Eddy Simulations of Wind Shear from Passing Vehicles Under a Freeway Overpass

California is moving toward a 100% clean energy future, and expanded wind energy will be a major component of the state’s future energy portfolio. Innovations in wind energy resources will move California closer to achieving its goal. To gain a better understanding of transient pressure and the wind shear generated at the bridge poles from passing vehicles, this study performed large-eddy simulations of a vehicle (also called an Ahmed body) moving under a freeway overpass at a distance of 0.75 w (width) from the bridge poles. Results include transient contours of mean velocity, turbulent kinetic energy, vorticity, and pressure around the vehicle and at the bridge poles at different time steps. Additionally, results indicate the vehicle’s base pressure changes with time, indicating the impact of the poles\u27 constraints on the vehicle\u27s drag. On the bridge poles, the location of the stagnation point changes with the passing of the vehicle, and the poles experience a transient load, with the peak load associated with the passage of the vehicle\u27s leading edge. The transient wind generated between the poles is mostly due to the vehicle’s front and decreases with the passing of the vehicle. The pressure at this location oscillates between a peak positive and a peak negative, generating a force potential for possible electric power generation. This data indicates the potential of capturing vehicle-generated wind energy for electric power generation, which could help California meet its clean energy goals and mitigate the negative impacts of climate change

Virus Control Aboard a Commuter Bus

A major health concern for public transit users is exposure to viruses from other passengers. This numerical study examines virus containment aboard a public bus with changes to the bus ventilation system. The virus was modeled as a 2.5 µm round solid particle released from the mouth of the infectious passenger at a rate of 21 particles per second at a mouth velocity of 0.278 m/sec. The air delivery to the cabin was two linear ceiling slots spanning the length of the bus delivering 59.38 m3/min (2,097 CFM) of air at a mean velocity of 1 m/sec. Two different axial and vertical linear exhaust slots placed on the side walls were investigated to examine how they affected virus containment and spread to the other parts of the cabin. Simulations were performed for both cases of the bus in transit and at the bus stop when the drop-off door was opened. Results indicate during transit that virus spread was contained to passengers sitting immediately in front of and behind the infectious passenger and the level of virus concentration could merit an increased risk of infection with increased virus residence time. However, augmented air mixing was observed between inside and outside air during the passenger drop-off with viruses spread to the front and back of the bus with reduced concentration and risk of infection. Analytical analyses of the risk of infection using the Wells-Riley equation were performed for the bus ventilation using 100% recirculating air without filtration, and 50% and 100% fresh air ventilation. Results indicate a high risk of infection when recirculating air is used, but the risk is reduced significantly with 50% and 100% fresh air ventilation. These results are critical to informing bus manufacturers, transit agencies, planners, and public transportation users about the potential of virus containment using a new ventilation system

Numerical Investigations of Virus Transport Aboard a Commuter Bus

The authors performed unsteady numerical simulations of virus/particle transport released from a hypothetical passenger aboard a commuter bus. The bus model was sized according to a typical city bus used to transport passengers within the city of Long Beach in California. The simulations were performed for the bus in transit and when the bus was at a bus stop opening the middle doors for 30 seconds for passenger boarding and drop off. The infected passenger was sitting in an aisle seat in the middle of the bus, releasing 1267 particles (viruses)/min. The bus ventilation system released air from two linear slots in the ceiling at 2097 cubic feet per minute (CFM) and the air was exhausted at the back of the bus. Results indicated high exposure for passengers sitting behind the infectious during the bus transit. With air exchange outside during the bus stop, particles were spread to seats in front of the infectious passenger, thus increasing the risk of infection for the passengers sitting in front of the infectious person. With higher exposure time, the risk of infection is increased. One of the most important factors in assessing infection risk of respiratory diseases is the spatial distribution of the airborne pathogens. The deposition of the particles/viruses within the human respiratory system depends on the size, shape, and weight of the virus, the morphology of the respiratory tract, as well as the subject’s breathing pattern. For the current investigation, the viruses are modeled as solid particles of fixed size. While the results provide details of particles transport within a bus along with the probable risk of infection for a short duration, however, these results should be taken as preliminary as there are other significant factors such as the virus’s survival rate, the size distribution of the virus, and the space ventilation rate and mixing that contribute to the risk of infection and have not been taken into account in this investigation

Numerical Investigations of Transient Wind Shear from Passing Vehicles Near a Road Structure (Part I: Unsteady Reynolds-Averaged Navier-Stokes Simulations)

In this research, the authors performed unsteady numerical simulations of a moving Ahmed body under a freeway overpass at different distances from the bridge columns in order to evaluate transient wind shear and the wind load on these columns. Results have shown that when the vehicle is at 0.75W distance from the bridge columns, an unsteady wind speed of up to 24 m/s is observed at the columns with a pressure coefficient difference of 0.9. Here W is the width of the vehicle. These results indicate with an appropriate system for harnessing these wind energy potentials, significant renewable electric power could be generated with zero carbon footprint

Evaluation of human obstructive sleep apnea using computational fluid dynamics.

Obstructive sleep apnea (OSA) severity might be correlated to the flow characteristics of the upper airways. We aimed to investigate the severity of OSA based on 3D models constructed from CT scans coupled with computational fluid dynamics (CFD) simulations. The CT scans of seven adult patients diagnosed with OSA were used to reconstruct the 3D models of the upper airways and CFD modeling and analyses were performed. Results from the fluid simulations were compared with the apnea-hypopnea index. Here we show a correlation between a CFD-based parameter, the adjusted pressure coefficient (Cp*), and the respective apnea-hypopnea index (Pearson's r = 0.91, p = 0.004), which suggests that the anatomical-based model coupled with CFD could provide functional and localized information for different regions of the upper airways

Large Eddy Simulations of Wind Shear From Passing Vehicles Under a Freeway Overpass

ZSB12017-SJAUXCalifornia is moving toward a 100% clean energy future, and expanded wind energy will be a major component of the state\u2019s future energy portfolio. Innovations in wind energy resources will move California closer to achieving its goal. To gain a better understanding of transient pressure and the wind shear generated at the bridge poles from passing vehicles, this study performed large-eddy simulations of a vehicle (also called an Ahmed body) moving under a freeway overpass at a distance of 0.75 w (width) from the bridge poles. Results include transient contours of mean velocity, turbulent kinetic energy, vorticity, and pressure around the vehicle and at the bridge poles at different time steps. Additionally, results indicate the vehicle\u2019s base pressure changes with time, indicating the impact of the poles' constraints on the vehicle's drag. On the bridge poles, the location of the stagnation point changes with the passing of the vehicle, and the poles experience a transient load, with the peak load associated with the passage of the vehicle's leading edge. The transient wind generated between the poles is mostly due to the vehicle\u2019s front and decreases with the passing of the vehicle. The pressure at this location oscillates between a peak positive and a peak negative, generating a force potential for possible electric power generation. This data indicates the potential of capturing vehicle-generated wind energy for electric power generation, which could help California meet its clean energy goals and mitigate the negative impacts of climate change