Numerical study of bone projectile points from the hillfort of Chernovskoe I

Using the method of computational fluid dynamics, we study the aerodynamics of projectile points excavated at the hillfort of Chernovskoe I in the Krasnokamsk urban district of Perm Krai (2nd–7th centuries AD). On the basis of numerically obtained values of drag coefficients, the projectile points were divided into two groups: those with the values ranging from 0.122 to 0.131 and those with the values from 0.161 to 0.221 (for a freestream velocity of 50 m/s). Within the second group, projectile points with obvious defects form a subgroup of arrowheads for which the drag coefficient exceeds 1.78. However, since asymmetry and curvature (interpreted as defects) vary continuously, this division cannot be precise. In order to evaluate the influence of the wake behind a projectile point, the drag forces acting on a point up to its shoulders were also calculated. The values of these drag forces show the same association with the presence of defects. However, the division into two groups is not preserved. Thus, the value of the drag coefficient can primarily be used to rank arrowheads according to their manufacturing quality. We also evaluated the measurement error due to the influence of the mesh resolution. The average error was 2%, while the maximum error reached 7% for a freestream velocity of 50 m/s.