Light-in-flight holography for visualization and velocimetry in three-dimensional flows

Area of Science:

• Fluid Dynamics
• Optical Engineering
• Holography

Background:

• Flow visualization and particle image velocimetry (PIV) are crucial for understanding fluid dynamics.
• Traditional methods often struggle with deep volumes, leading to noise from out-of-focus regions.
• Holographic techniques offer potential for high-resolution, volumetric flow analysis.

Purpose of the Study:

• To achieve flow visualization and PIV in deep volumes using holographic recordings.
• To implement light-in-flight holography to mitigate noise in reconstructed images.
• To demonstrate the capability of reconstructing thin, in-focus layers within a holographic volume.

Main Methods:

• Utilized light-in-flight holography with a ruby laser source of small coherence.
• Applied holographic recordings to capture flow data in deep volumes.
• Employed a reconstructing slit aperture on the hologram to select and isolate thin layers for analysis.

Main Results:

• Successfully reconstructed thin layers in depth without disturbance from the rest of the holographic field.
• Minimized noise from out-of-focus regions during image interrogation.
• Demonstrated applications in visualizing tracer particles in water and smoke in air flow.

Conclusions:

• Light-in-flight holography provides a robust method for volumetric flow visualization and PIV.
• The technique allows for precise selection of in-focus layers, enhancing data accuracy.
• This holographic approach is applicable to diverse fluid dynamics studies, including particle and smoke visualization.