New method for simultaneously measuring the angles of repose and frictional properties of wheat grains
J. Khazaei 1
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Department of Agrotechnology, College of Abouraihan, University of Tehran, P.O. Box. 11365/7117, Tehran, Iran
 
Int. Agrophys. 2010, 24(3): 275–286
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ABSTRACT
A new method was used for simultaneously measuring the angle of repose and friction coefficient of wheat grains. The method was based on the motion of the grains in a partially-filled horizontal rotating drum at the slumping and rolling modes of motion. Using this method it was also possible to determine two new physical parameters of wheat grains namely: lower angle of repose and upper angle of repose. The suitability of the new method was evaluated with the traditional methods. Measurement method had no significant effect (p = 0.01) on friction coefficient of wheat grains. The mean values of dynamic angle of repose of wheat grains obtained with the emptying and rotating drum methods had no significant difference (p= 0.01). With increasing the filling degree, the lower, upper, and dynamic angle of repose of wheat grains were increased. Rotation speed had no significant effect on upper and dynamic angle of repose. The differences between the lower and upper angle of repose lie in a small range of 1.34-7.65o, depending on the filling degree and rotation speed. The results confirmed that rotating drum method at filling degree of 0.222 and rotation speed of 3 r.p.m. can be used for simultaneously measuring the dynamic angle of repose and friction coefficient of wheat grains. The maximum difference between slumping and rolling dynamic angle of repose was less than 4.5% which implies that lower and upper angle of repose could be used adequately to estimate the dynamic angle of repose of wheat grains.
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