Modeling of subcritical penetration into sediments due to interface roughness

Area of Science:

• Underwater acoustics
• Geophysics
• Sediment acoustics

Background:

• Acoustic wave propagation in sediments is crucial for geophysical exploration and underwater acoustics.
• Previously, acoustic penetration below the critical angle in sandy sediments was experimentally observed but lacked a clear mechanistic explanation.
• Understanding subcritical acoustic penetration is vital for accurate seafloor characterization and sonar performance.

Purpose of the Study:

• To investigate and explain the mechanism behind acoustic penetration into sandy sediments at grazing angles below the critical angle.
• To develop and validate a numerical model simulating subcritical acoustic penetration.
• To assess the role of water-sediment interface roughness in acoustic wave propagation.

Main Methods:

• Utilized perturbation theory to develop a three-dimensional numerical model for simulating acoustic wave propagation.
• Employed formally averaged methods and single rough surface realizations to model scattering at the water-sediment interface.
• Conducted data-model comparisons to validate the proposed scattering mechanism.

Main Results:

• The study successfully simulated acoustic penetration into sandy sediments below the critical angle.
• Scattering from a rough water-sediment interface was identified as a key mechanism driving subcritical penetration.
• Model simulations aligned with experimental observations, supporting the proposed hypothesis.

Conclusions:

• Interface roughness scattering provides a viable explanation for observed subcritical acoustic penetration in sandy sediments.
• The developed numerical model is effective for simulating and understanding this phenomenon.
• Findings contribute to a better comprehension of acoustic wave behavior at the seafloor.