Dynamic shape factors of particles

Abstract A new method of shape characterization, first presented in connection with carbon black aggregates, is extended to a variety of shapes in two and three dimensions. This “dynamic” method is based on the representation of an object as an ellipsoid with equivalent radii of gyration about the central principal axes. This method gives two types of dimensionless shape factors, the anisometry (elongation and flatness) and the bulkiness, as well as the orientation. The anisometry factors and the orientation are in good agreement with the visual appearance of the objects. The bulkiness is generally reasonable but the validity of this shape factor is difficult to assess independently. The shape factors and orientation are calculated unequivocally from the coordinates of the contour. Rapid, practical methods are given for obtaining these coordinates in two dimensions, and a computer program is given for calculating the shape factors from these data for flat figures or for objects for which coordinates have been determined in successive layers.