AERMOD to Estimate Fugitive Dust Transport and Dispersion
Arid lands are subject to dust and sand storms caused by large wind-induced shear stresses over lands with reservoirs of soil materials which can become suspended. Conditions such as drought, poor agricultural practices, mining, and construction can causes lands to become more susceptible to wind erosion. The suspension of particulate matter (PM-10 and PM-2.5) can impact visibility and human health. For these reasons, the mechanisms causing dust and sand storms along with the ability to control them is an active area of research.
At the University of California at Davis, an Environmental Boundary Layer Wind Tunnel (Saltation Wind Tunnel) was used to simulated the first movement of dust from a soil surface. Traditionally, the saltation threshold had been determined based on the first sustained movement of sand grains; however, studies of natural soils consisting of dust and sand-sized particles showed that a sustained threshold of dust appeared prior to the initiation of sand movement. In this way an "Aeolian Threshold" for the natural soils was determined that included the dust particles which could be crucial in determining fugitive dust inventories and control methods. The facility for this research resides at the University of California at Davis. Dr. Roney modified the facility as needed for his research on Aeolian thresholds. Additional analysis of these experimental results was performed while Dr. Roney was an Assistant Professor at the University of Colorado at Colorado Springs resulting in a published paper.
A) Test Section
B) Turbulence Development Section
Aeolian Thresholds Determined with an Environmental Boundary Layer Wind Tunnel and Owens (dry) Lake soils
At the University of California at Davis, an Environmental Boundary Layer Wind Tunnel (Saltation Wind Tunnel) was used to simulate wind erosion by matching the near-surface turbulent boundary layer over a different soil surfaces at different wind velocities and frictional velocities. An experimental control-volume methodology was used to estimate the emission rates for Owens (dry) Lake soils. Testing also included the saltation of upwind sand over "emissive" soils. Additional analysis of these experimental results was performed while Dr. Roney was an Assistant Professor at the University of Colorado at Colorado Springs resulting in published paper.
Control volume analysis was used to estimate emission rates from soil surfaces in the Saltation Wind Tunnel (Roney and White, 2006).
Estimated emission rates as a function of the frictional velocity (Roney and White, 2006)
Estimated vertical flux to sand flux ratio compared to values obtained in field studies (Roney and White, 2006)
Numerical modeling of near-surface dust transport was performed with simple two-dimensional advection-diffusion equations. The surface boundary conditions were estimated from experimental wind-tunnel surface concentrations. The emission rates from the surface were estimated from the numerical simulations and compared to the experimentally determined values. Different mathematical forms of the surface boundary conditions were used to simulate physical conditions that may exist at the surface such as rippling, protection, and near-surface saturation.
Near-surface dust transport numerical simulation
The Saltation Wind Tunnel has been used to determine the effect of control strategies on emission rates. Past studies done at the University of California at Davis have included the effect of vegetation on controlling emission at Owens (dry) Lake. As part of Dr. Roney's work while at the University of Californa at Davis, he evaluated the effect of moisture content on highly emissive soils. In recent year's Dr. Roney has re-evaluated that work with relationship to existing literature on controlling construction and road dust. A paper based on new analysis of the previous work is forthcoming.
J.A. Roney, “Wind-Tunnel Physical Modeling and Numerical Simulation of Fugitive Dust Entrainment”, Presentation to the Department of Aerospace Engineering and Engineering Mechanics, Iowa State University, March 21, 2001
J.A. Roney, D. Kim, R.V. Coquilla, and B.R. White, “Simulation and Analysis of Factors Leading to High PM10 Emissions Fluxes at Owens Dry Lake Using an Environmental Boundary Layer Wind Tunnel”, Poster Presentation, AGU Fall Meeting, 1999.
D. Kim, J.A. Roney, R.V. Coquilla, and B.R. White, “Wind Tunnel Methods for Estimating Atmospheric Fugitive Dust Emissions”, Poster Presentation, AGU Fall Meeting, 1999.