Simultaneous multiple-point velocity measurements using laser-induced iodine fluorescence.

Area of Science:

• Fluid dynamics
• Laser-based diagnostics
• Spectroscopy

Background:

• Accurate measurement of velocity fields in gaseous flows is crucial for understanding complex phenomena.
• Existing techniques may lack the spatial resolution or non-intrusiveness required for certain applications.
• Iodine seeding offers a sensitive tracer for optical measurements in flow fields.

Purpose of the Study:

• To demonstrate a new technique for multi-point velocity measurement in gaseous flowfields.
• To validate the technique by comparing its results with numerical simulations.
• To assess the accuracy and limitations of the proposed measurement approach.

Main Methods:

• Utilizing Doppler-shifted absorption with fluorescence detection from iodine molecules.
• Exciting iodine with a tunable single-axial-mode argon-ion laser at 514.5 nm.
• Employing a 100 x 100 element photodiode array camera for simultaneous data acquisition at 10,000 points.

Main Results:

• Simultaneous velocity measurements were performed at 10,000 points in an iodine-seeded supersonic flowfield.
• The experimental measurements showed good agreement with a numerical solution for the velocity field.
• The accuracy of velocity component measurement was found to be limited to approximately +/-5 m/sec due to the iodine linewidth.

Conclusions:

• The demonstrated technique enables high-resolution, multi-point velocity measurements in gaseous flows.
• The method shows promise for applications requiring detailed flowfield characterization.
• Further refinement could improve the accuracy of the velocity measurements.