The Design, Fabrication and Testing of a Vertical Wind Tunnel for Determining the Aerodynamic Properties of Rice Paddies

Abstract

Grains are subjected to aerodynamic forces when they are separated, cleaned or conveyed pneumatically. The magnitude of these forces can be investigated in a wind tunnel. In this work, a vertical wind tunnel was developed to determine some aerodynamic properties of the rice paddies. Paddies of three varieties of New Rice for Africa (NERICA): L2, L3 and L4, were used in testing the performance of the vertical wind tunnel. The terminal velocities were determined. The Reynolds Numbers and the drag coefficient were calculated using empirical equations. These properties were determined at moisture contents of 12.78 %, 14.88 % and 13.48 % dry bases, for L2, L3 and L4, respectively. The average length of L2, L3 and L4 were respectively 9.670 mm, 10.174 mm and 9.770 mm. The length/width ratio of L2, L3 and L4 were 3.820, 3.963 and 3.931, respectively. Thus, the paddies could be classified as long and slender using the International Rice Research Institute (IRRI) standard for rice classification. The mean values of terminal velocities, drag coefficient, and Reynolds numbers for L2, L3 and L4 were 7.179 m/s, 7.106 m/s and 7.048 m/s; 8.304 × 10^-4, 8.589 × 10^-4 and 8.115 × 10^-4; and 1503.809, 1488.518 and 1474.692, respectively. Data on physical and aerodynamic properties of agricultural products are needed in the design and fabrication of machines for their harvesting, separation, cleaning, handling and storage.