Aerodynamic Properties of Tef for Separation from Chaff

Abstract

The knowledge of the aerodynamic characteristics of tef grains and chaff (floating velocity, aerodynamic resistance coefficient) is significant for the construction and operation of machines, which treat substances with air flow and in all cases when substances are moved in the air. Terminal velocity and drag coefficient of tef grain and straw materials (Kuncho variety) have been experimentally measured by suspending the particles in an air stream. The effects of moisture content of tef grain, node position and length of straw on terminal velocity were studied. The results showed that moisture content have significant effects (p<0.01) on terminal velocity. By increasing moisture content from 7.3 to 25.94 % (w.b.), its terminal velocity increased linearly from 2.98 to 3.87 m/s. Drag coefficient of the tef grain decrease from 0.77 to 0.59 as moisture content increase from 7.3 to 25.94 %.   The terminal velocity of the straws with different node positions (node free, end node, and middle node) and lengths (1 to 10 cm) were also measured.

Keywords: Aerodynamic properties, terminal velocity, drag coefficient, tef, straw, node

DOI: 10.7176/CER/11-3-05

Publication date: April 30^th 2019