Edge wave on axis behind an aperture or disk having a ragged edge

Area of Science:

• Acoustics
• Wave diffraction
• Fluid dynamics

Background:

• Diffraction phenomena are crucial in understanding wave propagation.
• Edge waves contribute significantly to the acoustic field behind apertures.
• The impact of edge irregularities on diffraction has been less explored.

Purpose of the Study:

• To theoretically and experimentally investigate diffraction by circular apertures with ragged edges.
• To model the contribution of ragged edges to the on-axis edge wave.
• To determine the effect of edge roughness on the root-mean-square (rms) pressure of the edge wave.

Main Methods:

• Modeling a ragged edge as N arcs of varying radii.
• Utilizing Kirchhoff theory for diffraction calculations.
• Deriving a formula for edge wave pressure based on incident wave properties.
• Conducting underwater measurements with spark-generated pulses.

Main Results:

• A theoretical formula was derived for the rms pressure of the edge wave.
• Predictions from the formula showed good agreement with experimental underwater measurements.
• The primary finding is that a ragged edge reduces the rms pressure of the edge wave.
• A specific edge profile was identified that can completely eliminate the edge wave.

Conclusions:

• Ragged edges offer a method to control and reduce edge wave effects in diffraction.
• The derived formula provides a tool for predicting edge wave behavior for various incident waves.
• This research has implications for acoustic design and wave manipulation in fluid systems.