1.6  MHz scanning rate direct absorption temperature measurements using a single vertical-cavity surface-emitting...

Area of Science:

• Fluid Dynamics
• Laser Spectroscopy
• Thermodynamics

Background:

• Shock waves are fundamental phenomena in fluid dynamics, crucial for understanding high-speed flows.
• Accurate, time-resolved temperature measurements are essential for validating shock wave models.
• Previous methods often lacked the temporal resolution to capture transient shock interactions.

Purpose of the Study:

• To develop and validate a non-intrusive, time-resolved temperature measurement technique for shock wave phenomena.
• To investigate the temperature field during normal shock reflection from a plane end wall.
• To compare experimental results with analytical predictions for shock tube flows.

Main Methods:

• Utilized a vertical-cavity surface-emitting laser (VCSEL) for tunable diode laser absorption spectroscopy (TDLAS).
• Employed water vapor as the probe species for temperature measurements.
• Operated the shock tube at a 1.6 MHz scan rate for high temporal resolution.
• Achieved a VCSEL modulation frequency of 800 kHz for rapid data acquisition.

Main Results:

• Successfully performed non-intrusive, time-resolved temperature measurements within a shock tube.
• Observed temperature measurements agreed within ±33 K standard deviation with analytical predictions.
• Demonstrated the capability to capture transient temperature variations during shock reflection.

Conclusions:

• The developed TDLAS technique provides accurate and rapid temperature measurements in transient shock wave events.
• This method is suitable for investigating complex, high-speed aerodynamic phenomena.
• The findings contribute to a better understanding of shock wave dynamics and thermal transport.