Leaky helical flexural wave backscattering contributions from tilted cylindrical shells in water: observations and...

Area of Science:

• Acoustics
• Wave phenomena
• Mechanical engineering

Background:

• Flexural helical waves are known to influence backscattering from cylindrical shells.
• Previous research focused on meridional ray coupling conditions at specific tilt angles.

Purpose of the Study:

• To investigate and model the contribution of flexural helical waves to backscattering from an empty cylinder at tilt angles below the meridional ray coupling condition.
• To compare experimental measurements with theoretical models, including ray theory and a partial-wave series solution.

Main Methods:

• Experiments were conducted using tone bursts on a tilted stainless steel cylindrical shell.
• Measurements analyzed contributions from flexural leaky Lamb waves above the coincidence frequency.
• Tone bursts of varying durations were used to observe superposition and separation of helical wave contributions.

Main Results:

• Flexural helical waves were found to significantly enhance backscattering for tilt angles smaller than the meridional ray coupling condition.
• Experimental data, particularly for ka = 20, aligned with the predictions of ray theory and the partial-wave model.
• The interference of successive helical wave contributions was shown to be crucial for quasi-steady-state backscattering amplitude.

Conclusions:

• Flexural helical waves play a significant role in the acoustic backscattering of cylindrical shells.
• The study validates the use of ray theory and partial-wave series models for predicting backscattering phenomena.
• Understanding these wave contributions is essential for accurate acoustic modeling of cylindrical structures.