Chaff Aerodynamics

Abstract

depend greatly upon the principal cross-section dimensions of the filaments. Aerodynamic forces and moment coefficients for each dipole configuration were computed from the photographic multi-image motion data using photogrammetric and aerodynamic data reduction programs developed as part of the effort. The resulting aerodynamic coefficient data were successfully correlated with Reynolds number, angle of attack, and various other parameters. While the force coefficients were found to be large and in general agreement with the various theories for creeping flow, the moment coefficients were extremely small and resulted primarily from configurational asymmetries. Using both the experimental data and theory, aerodynamic coefficient tables for representative dipole configurations, suitable for 6-DOF simulation of dipole motion, were prepared. These aerodynamic data were subsequently used in co, junction with a 6-DOF Monte Carlo trajectory program, modified for inclusion of stochastic atmospheric turbulence, for preliminary simulation of chaff dipole motion in both quiescent and turbulent atmospheres. Turbulence was found to have a large effect on the translational motion of the dipole, but only a small effect on its angular motion.

Research on the micromotion characteristics of a chaff cloud

“…However, the scholars did not study the micromotion characteristics of chaff clouds. The previous research on the characteristics of chaff clouds has involved three aspects: the aerodynamic characteristics [15], the statistical characteristics [16,17], and the echo characteristics [18][19][20]. Brunk et al [15] proposed a spiral descent motion model of a single chaff dipole by a lot of experiments.…”

“…The previous research on the characteristics of chaff clouds has involved three aspects: the aerodynamic characteristics [15], the statistical characteristics [16,17], and the echo characteristics [18][19][20]. Brunk et al [15] proposed a spiral descent motion model of a single chaff dipole by a lot of experiments. James et al [16] modified the operational hydrometeor classification algorithm (HCA) for the WSR-88D weather radar to include a chaff class that can be used as an input to a chaff detection algorithm.…”

Jamming recognition method based on the polarisation scattering characteristics of chaff clouds

“…Theoretical analyses and experimental results [4] indicate that the orientation distributions of chaff clouds can be classified into three typical cases: Case 1 : Assume that the chaff has a uniformly random orientation for all directions. The weight function in the PDF form is given as follows [2] Case 2 : Based on the experimental observations of [4], the chaff orientation can be approximated as linearity in the region over which it is non‐zero, and the probability density distribution for orientation can be taken as zero except within the region [6] Case 3 : The number of chaff oriented parallels to the xoy plane is larger than that of case 1. The weight function can be represented by a Gaussian distribution [16] where the weight function …”

“…In reality, the chaff clouds in the air will be affected by gravity, wind, the aerodynamic force, and moment caused by its own motions. However, since releasing chaff is generally tens of thousands, the orientation angles of chaff clouds are usually the statistical distribution [4, 6, 13]. Therefore, under this situation, according to the theoretical analysis and numerical results, it can be found that the parameter and are robust and effective discriminants, which can be applied in the recognition of chaff jamming.…”

“…The research on radar characteristics of chaff clouds mainly focuses on two aspects [2]: the aerodynamic characteristics of chaff clouds [3, 4] and the echo characteristics of chaff clouds [5–25]. The study of the echo characteristics of chaff clouds mainly involves the simulation of radar cross‐section (RCS) of chaff clouds [5–8], the statistical characteristics of RCS of chaff clouds [9], the spectral behaviour of chaff clouds [10], mode for chaff characterisation [11], effective permittivity of thin fibres [12], and the electromagnetic computation for dense chaff clouds [13–18].…”