UC Riverside

While environmental problems are complex and diversified, they can all be addressed by applying the fundamental principles of transport phenomenon. Transport phenomenon approaches these complex environmental issues by employing simple and basic equations that encompass the principles of mass, momentum, and energy transfer. This interdisciplinary research study combines experimental and computational approaches to investigate the complex dynamics involved in two such environmental applications; the dispersion of contaminants in indoor spaces and the factors contributing to wildfire ignition. Gaining a comprehensive understanding though these fundamental principles enable analysis and mitigation of associated environmental challenges. Computational fluid dynamic studies were deployed to understand the transmission of COVID-19 through exhaled droplets in common indoor spaces such as the supermarket checkout counter and a ride-share car. A combination of Lagrangian and Eulerian frameworks are used to simulate droplet dispersion, evaporation, and deposition on surfaces inside the supermarket and car where proximity to individuals is common. Integrating the droplet statistics with viral load distributions, this study helps explain the importance of inhalation exposures compared to surface contact observed in the pandemic. A similar study was then employed to determine the spread of E-cigarette emissions in enclosed spaces such as conference rooms, to investigate the secondhand and thirdhand exposure of E-cigarette emissions to occupants. Wildfires are being observed globally with growing frequency and are amplified by climate change-induced extreme weather conditions. In addition, ladder fuels which are usually shrubs or small trees in the forests pose a significant obstacle to prescribed burning, which is a prevalent method for mitigating chaparral crown fires in Southern California. These ladder fuels serve as conduits, facilitating the transition of surface fires into the forest canopy, thereby leading to the rapid spread of crown fires. As such, an experimental study was conducted to systematically investigate the vertical spread of wildfires due to the presence of ladder fuels. The effect of fireline intensity, heating duration, and crown base height on the ignition of elevated ladder fuels was investigated. The experimental observations were then used to evaluate a widely used semi-empirical model for successful crown layer ignition. The model showed good agreement with the experimental results.