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Acoustic wave propagation in structurally helical media.
1Dipartimento di Fisica del Politecnico di Torino and Istituto Nazionale di Fisica della Materia, C.so Duca degli Abruzzi 24, 10129 Torino, Italy.
Summary
Acoustic wave propagation in rotating solid media exhibits unique behaviors. Analysis reveals selective Bragg diffraction and acoustical rotation, with properties varying based on helical pitch and wavelength.
Area of Science:
- Solid-state physics
- Acoustics
- Materials science
Background:
- Periodically nonhomogeneous solid media with rotating stiffness tensors are of recent research interest.
- These materials have potential applications and require detailed acoustical property analysis.
Purpose of the Study:
- To theoretically analyze acoustic wave propagation in rotating anisotropic media.
- To derive simple, analytic propagation equations for detailed acoustical property assessment.
Main Methods:
- Theoretical analysis of acoustic wave propagation.
- Derivation of analytic propagation equations for periodically nonhomogeneous media.
- Investigation of axial propagation considering coupled and uncoupled field components.
Main Results:
- Uncoupled media show one forbidden band for selective Bragg diffraction.
- Coupled media exhibit a second forbidden band involving longitudinal and transversal modes.
- Acoustical rotation phenomena (pure, large, guided) are observed based on helical pitch to wavelength ratios.
Conclusions:
- The study provides a detailed understanding of acoustic wave behavior in rotating anisotropic solids.
- Findings highlight selective Bragg diffraction and diverse acoustical rotation effects.
- Analogies with optical properties and considerations for lossy/quasiaxial propagation are discussed.