Sinusoidal Vertical Motion of a Sonobuoy Suspension: Experimental Data and a Theoretical Model
Abstract
To isolate its acoustic sensor from the large vertical motions of the buoy at the ocean surface, a typical sonobuoy employs a low-pass mechanical filter comprising a bungee cord (spring) and a damper disk (hydrodynamic added mass and damping). If the system were to behave as a driven simple harmonic oscillator, the transfer function of vertical motion would roll off at 40 dB/decade above resonance; however, experimental systems of this sort exhibit a rolloff of approximately 30 dB/decade. Experiments have shown that the inertia coefficient CI and the drag coefficient CD of a circular disk in sinusoidal motion are in fact not constants, but depend on the dimensionless ratio of amplitude of motion to disk diameter, A/d. Incorporating this concept, the simple harmonic oscillator model has been enhanced to produce an iterative model for the transfer function of the bungee/disk system that agrees well with experimental data. Well above resonance, the model simplifies to an expression giving a 27 dB/decade rolloff.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 2008
- Accession Number
- ADA494786
Entities
People
- David M. F. Chapman
- Dusko B. A. Kezele
Organizations
- Defence Research and Development Canada