Events Calendar

Aerospace & Mechanical Engineering Seminar

Speaker: Michele Guala, Associate Professor/Unniversity of Minnesota

Talk Title: Wall Turbulence Structure in the Atmospheric Surface Layer. Scaling and Implications on Wind Turbine Siting

Abstract: The atmospheric surface layer, under special geophysical conditions, has been used as a canonical representation of wall turbulence flows at high Reynolds numbers. In this presentation I will describe how hotwire field measurements in the SLTEST (Utah) and Super-large-scale particle image velocimetry (SPIV, Hong et al., 2014, Toloui et al. 2014) during natural snowfalls in Minnesota, gave us the opportunity to explore atmospheric flows with unprecedentedly high spatio-temporal resolution. Results from SPIV measurements in the thermally neutral atmospheric surface layer, collected at the EOLOS field station over relatively flat, snow-covered farmland, will be introduced as a fully rough wall boundary layer with a Reynolds number Re ~10^6. The data include three time-resolved 15-minute acquisition periods with a field of view extending from 3 m to 19 m above the ground and up to 14 m wide. The flow statistics are validated and supplemented by sonic anemometers from a meteorological tower immediately downstream of the SPIV field of view. The time-resolved planar measurements provide temporal and spatial characterization of key wall turbulence features at high Reynolds number, including ramp-like structures, spanwise vortices, and uniform momentum zones. In comparing the findings to laboratory studies, Reynolds number similarity and the scaling behavior of characteristic properties will be discussed. The limitations of SPIV measurements will be presented using concepts of particle-turbulence interaction and further observations of snow flake dynamics. The impact of large scale flow measurements and turbulent motions will be discussed in the context of wind energy.

Host: Department of Aerospace and Mechanical Engineering

Location: Seaver Science Library (SSL) - 150

Audiences: Everyone Is Invited

Contact: Ashleen Knutsen