Estimation of projected surface area of irregularly shaped fragments

Abstract

The essence and the main contribution of this paper are consisted of the suggested novel method for estimation of a projected surface area of an irregularly shaped fragment, which represents a significant step toward a new method of an aerodynamic force estimation of a fragment motion through a resistive medium. The suggested method is to use a tri-axial ellipsoid that has a continuous surface (given as a mathematical function) to approximate an irregularly shaped fragment so that the fragment trajectory can be estimated faster taking into consideration that the aerodynamic force is proportional to a projected surface area of the fragment.During their motion, fragments can take any orientation relative to the velocity vector and aerodynamic force is proportional to a projected surface area of fragment perpendicular to the velocity vector, so it is necessary to have a method for correct estimation of the projected area in an arbitrary direction relatively to the fragment.The model was validated with analytical and CAD techniques, and verified using 3D model of a real fragment. The comparison of the projected surface area values for the fragment, obtained using the CAD tools and using our model, are generally in good agreement. This method represents a step toward modeling that does not require a CFD result for estimation of the aerodynamic force of irregularly shaped bodies. Keywords: Projected area, Fragments, Trajectory