Optical flow profiling method for visualization and evaluation of flow disturbances in agricultural pneumatic conveyance systems

• A flow-profiling apparatus and method is presented for dilute two-phase flows.
• The apparatus was applied to a laboratory air seeder simulator conveying wheat.
• Profiles were generated upstream, downstream, and around an obstruction.
• Obstruction effects on occurrence probability are presented.

Pneumatic conveying is widely used for transporting granular materials and agricultural products. Traditional flow visualization methods are used extensively in experimental fluid dynamics but have not been commonly used with agricultural products as the flow seeding particles. A flow visualization method was developed to aid in understanding physical design changes made to agricultural pneumatic conveying systems. This optical flow profiling method is demonstrated by providing qualitative flow images and quantitative values to describe the behaviour of the particle flow, both upstream and downstream of a 25 mm spherical obstruction. The sphere was attached to the bottom of an acrylic conveying line that was conveying wheat particles [equivalent diameter: 3.66 mm] at an air speed of 20 m/s and a mass flow rate of approximately 5 kg/min. Probability density maps of particle occurrence were developed to describe the chance of a wheat particle being present in a particular location of the conveying line. The data contained in these maps were used to determine the centroid of the distribution and to plot the change in the cross-sections over the test area of the pneumatic conveying system.