The PI-SWERL, which stands for Portable In-Situ Wind ERosion Lab, has been in development at DRI since 2000. The PI-SWERL concept was motivated by the need for a portable device to test and measure the potential for wind erosion and dust emissions from real-world surfaces.
PI-SWERL allows for elucidation of effects of specific road characteristics with respect to dust emissions. It can be used to assess the effect of pavement properties on dust emissions, potential for windblown dust on unpaved roads, effectiveness of surface treatments on reducing emissions, emissions from road shoulders, and potential for aerodynamically driven emissions for vehicles traveling at different speeds.
The PI-SWERL (US Patent 7,155,966) measures the amount of dust emitted from a surface when a known amount of wind shear is applied. A flat annular blade inside the chamber rotates at prescribed speeds to simulate different amounts of surface shear stress. Although it uses a different principal of operation, it can be thought of as analogous to a miniature wind tunnel.
The PI-SWERL was collocated with the University of Guelph large field wind tunnel at seventeen sites in the Mojave desert, spanning graveled roads to silty playas (Sweeney, et. al., 2008). Agreement between the two methods of estimating dust emissions was good with a correlation coefficient of 0.76 and a nearly 1:1 slope.
PI-SWERL data: PM10 dust emissions from a chemically treated test plot (right photo) normalized to dust emissions from a test plot that has not been treated (left) over 1 year exposure (Kavouras, et. al., 2007). X-axis: friction velocity (m/s) – a measure of surface wind shear.
PI-SWERL data: rapid non-linear increase in PM10 emissions with increase in aerodynamic shear (Pascals, N/m2, proportional to wind speed or tire stress) applied to paved road surface (China, 2008), indicating value of keeping speed limits low.
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