Multi-point FLEET velocimetry in a Mach 4 Ludwieg tube using a diffractive optical element

Area of Science:

• Fluid Dynamics and Aerodynamics
• Optical Measurement Techniques
• Laser-Based Diagnostics

Background:

• High-speed wind tunnels are crucial for aerospace research.
• Accurate flow velocity measurements are essential for understanding aerodynamic phenomena.
• Traditional velocimetry methods can have limitations in complex flow environments.

Purpose of the Study:

• To develop and evaluate novel configurations for femtosecond laser electronic excitation tagging (FLEET) velocimetry.
• To investigate the use of diffractive optical elements for enhanced FLEET measurements.
• To demonstrate the utility of these techniques in a Mach 4 Ludwieg tube.

Main Methods:

• Integration of a diffractive optical element with FLEET velocimetry.
• Exploration of two viewing configurations: orthogonal and parallel to the laser beam axis.
• Demonstration in a Mach 4 Ludwieg tube for high-speed flow characterization.

Main Results:

• The parallel viewing configuration allows for wall-normal FLEET measurements.
• This configuration avoids direct laser impingement on the surface.
• Successful probing of multiple locations in a high-speed flow environment.

Conclusions:

• The combined use of diffractive optics and FLEET velocimetry offers a versatile tool for high-speed flow diagnostics.
• The parallel viewing approach provides a significant advantage for wall-bounded flow measurements.
• This technique enhances the capability for detailed aerodynamic analysis in wind tunnel testing.