A Controlled-Environment, Field-Deployable (CEFD) Wind Tunnel to Enable Fundamental Research in Aeolian Transport
Abstract
Aeolian transport and dust emission have significant impact on climate and global biogeochemistry, but also pose serious hazards for human safety and equipment operation/maintenance. This proposal requests funds to construct a new field wind tunnel that will enable unique measurements related to aeolian transport and dust emission. Though climate-controlled wind tunnels exit, as do field wind tunnels, climate-controlled field wind tunnels do not yet exist. Indeed, even the current controlled-environment wind tunnels do not have the ability to control light levels, a key determinant of evaporation and aggregate formation in natural soils. The planned controlled-environment, field-deployable (CEFD) wind tunnel will fill this gap and will be used to address questions that are of interest to the DoD related to aeolian transport and dust emission. The proposed CEFD tunnel will be based on the modular design of the UCLA Portable Aeolian Laboratory (PAL). A recirculating design is required for control of temperature and humidity within the tunnel. Therefore, as a stand-alone tunnel, the CEFD tunnel will differ from the UCLA PAL in that it will recirculate air and will have environmental controls so that temperature, humidity, and light levels can be manipulated within the test section. We plan on a series of rigorous tests for the CEFD tunnel to determine the limits and stability of wind speed, temperature, and relative humidity control that can be obtained and to ensure these limits are within our design parameters. Upon successful completion of the tests, we will conduct experiments pertaining to an area of research currently funded by the DoD: How and when does precipitation impact dust emission? One of the tasks for the funded work is to test the hypothesis that soil moisture from precipitation rarely inhibits aeolian transport because, if wind events occur after the active layer (i.e., the top 2 mm of soil) has dried, then precipitation will have little effect on the threshold for transport. Understanding the interplay of wind and precipitation events in controlling aeolian transport and dust emission is, in part, limited by knowledge of the time it takes for the active layer to dry. Because evaporation is controlled by radiation and wind shear velocity, in addition to temperature Therefore, the first applications of the CEFD tunnel will be to conduct a series of dry-down experiments on natural soils of varying textures. We will vary temperature, relative humidity, light levels, and below-threshold wind speed to better parameterize dry-down under a range of realistic field conditions. This improved dataset will enable much better understanding of the conditions in which precipitation impacts aeolian transport and dust emission globally. The second application of the CEFD tunnel will be to study the complex dynamics in the interplay of drying, aeolian transport, and re-exposure of wet sand. As an extension of the planned dry-down experiments, using different temperatures, light levels, and above-threshold wind conditions, we will quantify the temporal evolution of aeolian transport as the surface soil dries and continues to expose wet soils when dry layers are transported. he third application of the CEFD tunnel will be to probe how saltation impacts the rate of soil drying as a result of the rapid drying of particles ejected from the surface through sand blasting. To study this phenomenon, we will conduct drying experiments with introduced saltators to compare the temporal evolution of transport with and without introduced saltators at a variety of temperature, humidity, and light conditions. Together this set of experiments, which can only be conducted by a CEFD tunnel, will answer critical questions about the interplay of wind and water in the production of dust from natural soils.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 28, 2019
- Source ID
- W911NF1910251
Entities
People
- Gregory S. Okin
Organizations
- Army Contracting Command
- United States Army
- University of California, Los Angeles