Tomographic reconstruction of stratified fluid flow

Area of Science:

• Fluid dynamics
• Acoustic imaging
• Computational physics

Background:

• Imaging fluid flow is challenging due to fluid motion.
• Accurate measurement of fluid velocity and sound speed is crucial for understanding complex flow phenomena.
• Current methods may lack the resolution or capability to capture detailed flow characteristics.

Purpose of the Study:

• To propose and evaluate a new method for imaging moving fluids using acoustic waves.
• To develop algorithms for reconstructing sound speed and fluid vorticity from acoustic travel time data.
• To demonstrate the efficacy of the proposed method through numerical simulations.

Main Methods:

• Utilizing high-frequency acoustic waves to probe a fluid cross-section from multiple directions.
• Applying principles of straight-ray geometric acoustics to relate travel times to sound speed and fluid velocity.
• Developing and implementing a novel filtered backprojection algorithm specifically for vorticity reconstruction.
• Simulating a 3D stratified fluid and calculating acoustic travel times via path integration.

Main Results:

• Successfully isolated projections of sound speed and velocity by combining travel times.
• Reconstructed the scalar sound speed using a standard filtered backprojection algorithm.
• Recovered the component of fluid vorticity transverse to the plane of insonification, despite limitations in complete velocity inversion.
• Demonstrated the inversion procedure by accurately recovering sound speed and vorticity in a simulated 3D stratified fluid.

Conclusions:

• The proposed acoustic imaging method is effective for visualizing moving fluids.
• The developed filtered backprojection algorithm enables the reconstruction of fluid vorticity.
• This technique offers a promising approach for quantitative analysis of complex fluid flows.