Testing and modeling of a spiral wave front beacon for use in navigation.

Abstract

A beacon with two cylindrical elements of 3-1 composite material has been developed, tested, and modeled for use in navigation. The displacement of each element is radial and the phase of the outgoing wave front is determined by the cross-section of the cylinder. One element, the reference, has a circular cross-section which produces circular wave fronts. The second element has a radius that varies linearly with angle such that there is a displacement of one wavelength over 360 deg; the resulting wave front is spiral. This beacon improves on a prototype presented at a prior meeting [Dzikowicz and Hefner, J. Acoust. Soc. Am. 125, 2540 (2009)]. Results from experiments conducted at the Naval Surface Warfare Center, Panama City Division are compared with finite element models. Surface displacement of the elements is determined by the use of laser Doppler vibrometry. Variation in the field due to geometry and surface displacement variation are discussed. A simple navigational test shows the efficacy of the beacon. [Work supported by the Office of Naval Research.]