Project Number: 3020-43440-009-09-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2020
End Date: Aug 31, 2022
The objectives of this research are to extend current computational fluid dynamics (CFD) models and discrete element method (DEM) for postharvest storage and insect control to: (1) CFD modeling of aerosol distribution for stored product insect control in warehouses, and (2) include effects of particle size distribution on DEM modeling of compaction of wheat during uniaxial compression.
Aerosol insecticides (e.g., pyrethrins) are widely used for control of stored products insects inside food facilities. The effectiveness of aerosol applications in food facilities is dependent on the droplet movement due to aerodynamics, gravity, and airflow patterns. Aerosol droplets must contact the surfaces and be trapped for the insects to contact the insecticide and mortality to then occur. To optimize pyrethrin aerosol application, computational fluid dynamics models will be developed to simulate airflow and droplet movement in enclosures, such as grain milling facilities. A discrete phase model in Ansys Fluent will be used to track pyrethrin droplets of various sizes (0.1 to 20 µm) and determine their deposition on surfaces. Simulations will use uncoupled and steady particle tracking wherein the motion of the aerosol droplets did not influence the airflow, the particles do not interact with each other, and are tracked one at a time in the domain. Techniques developed in an existing two-dimensional, axisymmetric, multiphase flow will be extended to 3-dimensinal models. The three-dimensional multiphase flow model will be developed to simulate induced airflow and droplet flows from an aerosol spray nozzle in room with no obstructions. This will simulate aerosol spray tests conducted in the ARS Manhattan, KS, spray-test facility. After validation of the empty room configuration, the 3-dimensional multiphase flow model will be extended to simulate the air and droplet flows in the same room with simple obstructions included. Two sizes of individual rectangular obstructions (0.5 × 0.75 × 1.0 m and 1.0 × 1.5 × 2.0 m) will be simulated; first situated directly on the floor, then located 0.5 and 1.0 m above the floor, and then with both obstructions in the room at the same time. Subsequently, this 3-dimensional multiphase flow model can be extended to simulate the main room of an existing wheat milling facility with milling equipment in place as obstructions. Current discrete element method models of uniaxial compression of bulk stored grain need to be refined regarding the effects of particle shape and particle size distribution to properly account for these particle effects. The compressibility phenomena in the laboratory uniaxial compression tester will be modeled using the discrete element method to study the individual particle rearrangement and compaction that produces the well-known bulk compaction of the grain. A full range of particle shapes will be investigated as well as the maximum range of particle size distributions typically found in the U.S. for common cereal grains. This detailed knowledge of the particle-level processes leading to bulk compaction can be used to better predict compaction in grain bins.