Terminal Velocity of Wheat Stem Nodes versus Internodes for Similar Particle Dimensions

Highlights Terminal velocities were measured for wheat stem nodes and internodes for similar particle dimensions to investigate the feasibility of aerodynamic separation. Mean measures of terminal velocities for wheat stem nodes and internodes were 4.91 and 3.35 m s-1, respectively, that coincided with values of 4.92 and 3.37 m s-1 calculated for spherical particles (Mohsenin, 1970). Wheat stem particle mass ranged from 0.015 (internode) to 0.041 g (node) that significantly correlated with terminal velocity ranging from 3.13 to 5.14 m s-1, respectively. Wheat stem particle density ranged from 112 to 297 kg m-3 that significantly correlated with terminal velocity ranging from 3.12 to 5.11 m s-1, respectively. Abstract. Efficient separation of physiological plant components potentially improved the targeting of components to best uses. The terminal velocity property used an opposing air velocity to equilibrate particle weight with the sum of the drag and buoyancy forces. This study used particles of similar dimensions to ascertain the effect of particle mass and density on experimental measures of terminal velocity in a wind tunnel and as calculated by reliable equations. Similar particle diameters, lengths, and volumes of wheat stems ranged from 0.362 to 0.376 cm, 1.25 to 1.28 cm, and 0.131 to 0.141 cm3, respectively. Moisture content was 12% wet basis. Wheat stem internodes had individual particle mass and density ranging from 0.015 to 0.019 g and 113 to 144 kg m-3, respectively, and mean Terminal Velocity Wind Tunnel (TVWT) terminal velocities for wheat stem internodes that ranged from 3.13 to 3.58 m s-1. Nodes had individual particle mass and density ranging from 0.031 to 0.041 g and 236 to 297 kg m-3, respectively, and mean TVWT terminal velocities for wheat stem nodes that ranged from 4.62 to 5.14 m s-1. Thus, no overlap in values was observed for particle mass, particle density, and terminal velocity between wheat stem internode and wheat stem node. This observation supports the potential of using terminal velocity to separate node from internode for similar-sized wheat stems at a given moisture content. Keywords: Aerodynamic separation, Anatomical component, Biomass property, Physical experiment, Sorting, Terminal velocity, Vertical wind tunnel, Wheat stem particles.