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United States Department of Agriculture

Agricultural Research Service

Research Project: Mechanistic Modeling of Wind Barriers and Grain Commingling Using Cfd and Dem

Location: Engineering and Wind Erosion Research Unit

2013 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:

An open-source software package for computational fluid dynamics (OpenFOAM) was evaluated together with open-source pre-processing (Salome) and post-processing (Paraview) software products. Preliminary modeling tests were conducted by using known fluid flow models for validating the capabilities of the software. This will be extended for use with airflow through vegetative barriers and multiphase flow (dust particles and air). Measurements will compare the results of optical porosity determination via photogrammetry and porosity measurements via a pressure drop method using cup anemometers. Initial field sites have been selected and tests will be conducted this summer and fall.

Simulations were performed to determine the parameters required for improved particle models for sound corn and wheat kernels for use in discrete element modeling of grain handling. The new models were compared to see which characterized bulk grain behavior best in simulations of: (1) bulk density measurements, (2) angle of repose tests, and (3) hopper flow. The parameters evaluated were particle restitution coefficient, static friction coefficients, rolling friction coefficients, particle size distribution, and shear modulus. Literature values for the bulk grain behavior were used when possible and supplemented with results from laboratory experiments of hopper flow characteristics at moisture content levels of 10%, 12%, and 14% wet basis. Data were also obtained for particle density and single kernel mass of corn and wheat infested with rice weevil and lesser grain borer, respectively; these data are being used to develop improved particle models for infested kernels mixed with sound kernels for developing best management practices for reducing unwanted commingling of infested grain in bucket elevator boots.


Last Modified: 7/28/2014
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