Three-dimensional dynamic measurement of irregular stringy objects via digital holography.

Area of Science:

• Fluid dynamics
• Optical metrology

Background:

• Dynamic stringy objects, such as liquid rims and ligaments, are crucial in multiphase fuel droplet breakup.
• Accurate measurement of these complex structures is challenging.

Purpose of the Study:

• To develop and validate a novel method for automatic measurement of dynamic stringy objects using digital in-line holography.
• To characterize the spatial-temporal evolution of liquid rims during droplet breakup.

Main Methods:

• A hybrid approach combining digital in-line holography with image processing techniques.
• Extraction and sizing of object sections along a skeleton in extended depth-of-field images.
• Stitching of surface points for full object reconstruction.

Main Results:

• Validation on a static spring demonstrated high accuracy with local thickness errors <5.3% and z errors <230 μm.
• Successful characterization of liquid rim evolution during aerodynamic droplet breakup.
• Continuous capture of rim/ligament structures over 1.58 ms across seven frames.

Conclusions:

• Digital in-line holography is extended as an effective 3D diagnostic tool for dynamic stringy objects.
• The developed method provides accurate and detailed insights into fluid breakup phenomena.
• Enables advanced understanding of complex fluid dynamics in applications like fuel injection.