An airborne acoustic method to reconstruct a dynamically rough flow surface.

Area of Science:

• Fluid dynamics
• Acoustics
• Geophysics

Background:

• Accurate measurement of dynamic water surface elevation is crucial for understanding turbulent flow.
• Existing airborne methods lack the high fidelity needed for instantaneous surface reconstruction.
• Surface roughness patterns are known indicators of underlying hydraulic processes.

Purpose of the Study:

• To propose and validate a novel airborne holographic acoustic method for reconstructing dynamic water surface elevation.
• To demonstrate the method's capability for non-invasive flow mapping and characterization.
• To achieve sub-millimeter accuracy in surface elevation reconstruction.

Main Methods:

• Development of a holographic acoustic method utilizing airborne acoustic pressure data.
• Validation using synthetic data generated with Kirchhoff approximation and finite difference time domain methods.
• Application to measured surface roughness patterns of turbulent water flows.

Main Results:

• Successful reconstruction of one-dimensional rough water surface elevation from airborne acoustic data.
• Achieved sub-millimeter accuracy in surface elevation reconstruction.
• Demonstrated practical implementation using microphone arrays or a traversed single microphone.

Conclusions:

• The proposed holographic acoustic method provides a high-fidelity, non-invasive solution for measuring dynamic water surface elevation.
• This technique enables accurate characterization of turbulent flow dynamics through surface roughness analysis.
• The method paves the way for new acoustic holography-based instrumentation for fluid flow research.