Current Science

T. Sai Teja ¹, Manoj B. Vaghela ¹, Avijit Chatterjee ¹

Affiliations
1 Department of Aerospace Engineering, Indian Institute of Technology Bombay, Mumbai 400 076, IN

Abstract

Serrations at trailing edges of aircraft wing have long been known to suppress flow noise by suitably altering the flow at the trailing edge. Serrations at trailing edges are now also being used to reduce surface edge return contribution in scattering of electromagnetic waves by combat aircraft wing in order to reduce detectability by radar. A study was carried out on the efficacy of trailing edge serrations found in the wing of a barn owl, formed by its primary remiges or flight feathers, towards minimizing trailing edge related contributions by a common combat aircraft wing in an electromagnetic field. The barn owl is especially well known for its silent flight which is usually attributed to multiple adaptations in its wings including at the trailing edge. Barn owl type trailing edge serrations are appended to a planar metallic delta wing and subjected to an incident electromagnetic field. Electromagnetic scattering is predicted by numerically solving Maxwell's equations using a finite volume time domain method and the radar cross-section calculated.

Keywords

Barn Owl, Finite Volume Time Domain, Maxwell’s Equations, Radar Cross-Section, Stealth, Serrations.

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Karri Sai Krishna Reddy ¹, Avijit Chatterjee ¹

Affiliations
1 Department of Aerospace Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, IN

Abstract

Serrations are found in nature on the leading edge (LE) of bird wings and whale flippers. These serrations reduce flight noise and improve aerodynamic performance. This has inspired LE serrations to be incorporated in the design of aircraft wings and turbine blades. LE of wings can contribute significantly to observability of aircraft by radar due to LE diffraction of horizontally polarized incident electromagnetic (EM) waves. Serrations at the wing LE can also be used to reduce observability to radar under such circumstances. In the present study, the method of equivalent currents is used to analyse the effect of microserrations on an infinitesimally thin metallic delta wing. It is shown that microserrations at the wing LE can be effectively used to control backscatter due to diffraction of EM waves at the wing LE. LE serrations, in general, work by introducing a randomness in the interaction of wing LE with incident fluid flow or EM field.

Keywords

Computational Electromagnetics, Leading Edge, Radar Cross-Section, Serrations, Wing Observability.

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