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United States Department of Agriculture

Agricultural Research Service


Location: Engineering and Wind Erosion Research Unit

2012 Annual Report

1a.Objectives (from AD-416):
Develop mechanistic simulation models of: (1) airflow through and around vegetative wind barriers using Computational fluid dynamics (CFD) to facilitate improving the characterization of wind barriers in wind erosion modeling and (2) grain handling in elevator equipment using the discrete element method (DEM) to facilitate improved identity preserved (IP) grain handling operations.

1b.Approach (from AD-416):
Computational fluid dynamics (CFD) models of airflow around and through wind barriers will be developed for porous vegetative barriers. The standard k–e model will be used for modeling turbulence and the governing equations will be discretized using a first order upwind scheme. The models will be refined and then validated by comparing predicted air velocities with published data. The validated CFD model will be applied to simulate airflow through and dust particle collection by single rows of trees during different seasons and with different barrier heights.

The discrete element method (DEM) will be used to model adventitious grain commingling in bucket elevator legs. Existing particle models for corn, soybeans, and wheat will be used to create grain handling models in 3-d and quasi-2-d. The models will be applied to full-scale legs to evaluate the effect of: (1) operating parameters (flow rate, grain type, and cleanout procedures) and (2) design factors (uptake side, boot size, and cup design) on adventitious commingling levels. Preferred operating conditions and design characteristics for reducing undesirable commingling will then be evaluated.

3.Progress Report:

A literature search showed that methodologies, such as photogrammetry, for vegetative barrier assessment are low-cost but provide a less accurate and two-dimensional assessment of tree porosity. Laser-based protocols for determining tree porosities are beneficial by providing complex parameters (especially three-dimensional representations) but are limited by equipment cost and training. Numerical simulations will be done and will be validated with field tests to determine optimal barrier characteristics.

Adventitious grain commingling in a pilot-scale bucket elevator boot system was simulated using three-dimensional (3-D) discrete-element method (DEM) models and validated with experimental data. Approximately ninety-three DEM models were evaluated by grain type, residual grains, boot size, particle generation and flow rate, and uptake side (i.e., front- or back-loading) to determine which DEM model best simulate the grain commingling. Appropriate validated particle models of corn and wheat kernels selected from simulated bulk grain property tests were used in the DEM boot models. The validated particle and boot models are being applied to full-scale boots to determine best management practices for predicting and reducing unwanted grain commingling.

Last Modified: 7/23/2014
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