Trajectory Simulation of Chaff Dipoles of Slender Circular Cylinder

摘要

The flight behavior of chaff is numerically investigated. Numerical simulations have been performed to understand the flight behavior of both single chaff dipole and multiple chaff dipoles, including the effect of geometric curvature. For this purpose, a numerical methodology for simulating the trajectory of chaff dipoles is developed. The methodology is a fully coupled process, which consists of an aerodynamics part and a trajectory simulation part. Chaff as a countermeasure is generally assumed to be slender circular cylinder with very small diameter, which corresponds to a Reynolds number of unity. To obtain the normal force at this low Reynolds number, a curve-fit formula offered by Sucker and Brauer is used, while an analytic solution offered by Curie is used to obtain the tangential force. As a result of trajectory simulation, it was found that the elevation angle of a single dipole maintains its initial orientation while that of a bent dipole tends to be horizontal with respect to the ground. This phenomenon makes the difference of position distribution between a chaff cloud of straight dipoles and that of bent dipoles.