New Method of Measuring the Angle of Repose of Hard Wheat Grain

In this work a new optical method of measuring the static angles of repose of hard wheat grain is presented. Conventional methods of measuring angle of repose are based on manual measurements of angle by protractor or calculation from measured diameter and height of the pile using the trigonometric equation. These methods are based on the assumption that the stacked grains form a symmetrical cone, and the left and right contact angles are equal, which is not correct as grain piles are rarely of an ideal cone shape with perfectly straight surfaces. To address the limitations of these standard methods we are introducing a new method based on the real shape of a grain pile taken by photographic image. These images taken by a digital camera were analysed to allow the calculation of the angle of repose using computer software. For this work a low cost web camera connected to the note book computer and freely available software Image J were used. Measurements of the angle of repose for several wheat grain piles using existing and the new method were performed. Our results indicate slight disagreement between these two methods showing 10 to 15° higher values for the new optical method proving it to be more accurate.