Angular scattering of sound from solid particles in turbulent suspension.

Area of Science:

• Acoustics
• Fluid Dynamics
• Materials Science

Background:

• Sound scattering is crucial for understanding particle dynamics in fluid flows.
• Turbulent jets with suspended particles present complex acoustic scattering scenarios.
• Characterizing particle shape effects on scattering is essential for accurate modeling.

Purpose of the Study:

• To investigate sound scattering by solid particles in a turbulent jet.
• To compare scattering from spherical and aspherical particles.
• To evaluate the applicability of scattering models to irregular particles.

Main Methods:

• Acoustic scattering measurements were performed in a bistatic geometry.
• Frequencies ranged from 1.5 to 4.0 MHz, with scattering angles from 95 to 165 degrees.
• Experiments used lead-glass beads and natural sand grains of varying sizes (0.7 < ka < 4).

Main Results:

• Lead-glass bead scattering matched elastic sphere model predictions.
• A rigid movable sphere model best fit sand grain data, with diameter within 4% of equivalent volume.
• Sand grain scattering patterns were smoother than predicted, with muted angular undulations.

Conclusions:

• Elastic sphere models are suitable for nearly spherical particles.
• Rigid movable sphere models offer a good approximation for aspherical particles.
• Irregular particle surfaces disrupt creeping wave interference, leading to smoother scattering patterns than predicted by spherical scatterer theory.