Events Calendar

Astani Civil and Environmental Engineering Seminar

Speaker: Scott C. James, Principal Member of the Technical Staff, Sandia National Laboratories

Talk Title: Reactive Flow and Transport in Environmental Systems: Energy Considerations

Abstract: This presentation is a compilation of some of my research interests that span the fields of groundwater hydrology, surface-water hydrology, and renewable energy (e.g., algal biofuels and marine hydrokinetic energy). More specifically, my research developments in the areas of (a) colloid transport in fractured formations, (b) computational fluid dynamics simulations for marine hydrokinetic energy, and (c) optimizing algae growth in open-channel raceways for biofuel production will be presented.

Analytical, theoretical, and computational investigations examining fate and transport of colloid and contaminant plumes in fractured porous media were conducted. Initially, analytical solutions to the mathematical model describing the transport of finitely sized colloids in a uniform-aperture fracture subject to several different boundary conditions were developed. A novel particle tracking algorithm was verified through comparisons to newly developed analytical solutions. This particle-tracking algorithm was used to examine general transport characteristics of polydisperse colloid plumes in a uniform aperture fracture, focusing on the effects of their finite size. Finally, because natural fractures are rough, the particle tracking algorithm was extended to examine colloid and contaminant co-transport within a quasi-three-dimensional spatially-variable-aperture fracture.

Marine hydrokinetic (MHK) energy research was conducted to gain a better understanding of how to convert energy (momentum) from a system with minimum impact on the marine environment. The EPA’s Environmental Fluid Dynamics (EFDC) code was modified to represent

MHK devices as momentum sinks with commensurate adjustments to the turbulent k- terms. Turbulence equation coefficients were calibrated to ensure that simulated wakes from a turbine in a laboratory flume matched the experimental data. Also, the sediment dynamics algorithms were updated to include a unified treatment of cohesive and noncohesive sediments as well as effects of bedslope and consolidation. Removing energy from a system can result in changes to circulation including decreased water-level ranges and increased residence times. The model helps determine an appropriate amount of energy that can be generated from an MHK site – an amount that prevents environmental degradation while also suggesting device locations that optimize energy capture.

Significant research on algae growth in open-channel raceways was conducted to better understand the important parameters affecting biomass production with the goal of achieving cost-competitive biofuels. Water-quality algorithms in EFDC were modified and improved to be applicable to high-density algal systems and to account for the effects of growth limitation as a function of CO2 concentrations and pH fluctuations. The model faithfully reproduced a few simple algae growth test problems and was easily extended to accurately simulate the data collected from an algae growth experiment conducted in a greenhouse. Working in conjunction with industry partners, the model is currently employed for the simulation of algae growth in various conceptual models of open-channel raceways.

Fluid dynamics research is integral to developing alternative energy platforms. Water and energy are inextricably coupled; it is virtually impossible to consider one independently from the other. Given the emphasis on energy and the environment, an environmental engineer must employ broad civil and mechanical engineering skills to tackle this multidisciplinary field.


Host: Sonny Astani Department of Civil and Environmental Engineering

Location: Kaprielian Hall (KAP) - 209

Audiences: Everyone Is Invited

Contact: Cassie Cremeans