|Van Pelt, Robert - Scott|
|BADDOCK, MATTHEW - Collaborator|
Submitted to: International Conference on Aeolian Research
Publication Type: Abstract Only
Publication Acceptance Date: 4/30/2014
Publication Date: 7/21/2014
Citation: Zobeck, T.M., Van Pelt, R.S., Baddock, M. 2014. Adventures in Using a Portable Wind Tunnel. Eighth International Conference on Aeolian Research. July 21-25, 2014, Lanzhou, China, p. 2.
Technical Abstract: Wind erosion is a natural process that often occurs wherever loose, dry, erodible soil is exposed to strong erosive winds. The study of wind erosion in the field is quite challenging, with the researcher at the mercy of an unpredictable, large variation in weather factors affecting the outcome. Field portable wind tunnels have been used to measure wind erosion on undisturbed natural surfaces in an effort reduce the uncertainty and vagaries of relying on natural winds. Portable wind tunnels permit studies of wind erosion under a wide selection of soils, vegetation, and management conditions on relatively small plot areas. However, proper use of a portable wind tunnel requires careful preparation and knowledge of the wind profile and soil surface characteristics. The wind tunnel should be designed to ensure a logarithmic boundary layer is formed and the tunnel has proper dimensions to allow development of wind erosion processes without interference with tunnel structures. When sampling eroding particles, care must be taken to consider the specific purpose of sampling and employ proper equipment. Sampling equipment often include passive saltation samplers, active dust collectors employing an aspirated sampler to obtain isokinetic conditions, and particle impact sensors to monitor particle movement. Care must be taken to account for the horizontal and vertical variation in sediment transport. We designed a portable wind tunnel that uses a centrifugal blower, a flow-conditioning section with an optional abrader material feed system, and a 1 m tall and 0.5 m wide working section varying from 2 to 6 m in length. We use a 1 m tall, 3 mm wide slot-sampler at the tunnel midline to isokinetically sample the dust and saltation-size material. Dust is measured using an optical particle sensor and by weighing dust deposited on large filters. At times, we have also employed other higher volume samplers for specific studies. We monitor particle impacts with a Sensit or Wenglor particle impact sensor. The wind tunnel has been used throughout the US to study a variety of surfaces and conditions. Studies have been conducted in New Mexico to investigate the effects of cattle traffic on dry lakebeds and semiarid grasslands and the effects of burning in shrub invaded grasslands on wind erosion. Evaluations of the effects of various cropping systems on wind erosion of silty soils have been conducted in Kansas and Colorado. Organic soils erodibility has been measured in Michigan and Florida. The organic soils studies included an analysis of the types of bacteria carried in different wind-eroded sediments. Finally, the erodibility of several bare sandy soils has been quantified in Texas. In this paper, we will discuss the development and testing of the Texas portable wind tunnel, present details on our measurement scheme, and describe several of our sampling campaign experiences.