Hypersonic wake velocity measurements using acetone molecular tagging velocimetry

Area of Science:

• Fluid Dynamics
• Aerospace Engineering
• Laser Diagnostics

Background:

• Hypersonic flow research is crucial for aerospace applications.
• Understanding wake dynamics behind objects is essential for vehicle design.
• Minimally intrusive measurement techniques are needed for high-speed flows.

Purpose of the Study:

• To quantitatively measure velocity in the wake of spheres under hypersonic conditions using Molecular Tagging Velocimetry (MTV).
• To compare experimental MTV data with computational fluid dynamics (CFD) simulations.
• To assess the accuracy and applicability of MTV in hypersonic flow environments.

Main Methods:

• Utilized Molecular Tagging Velocimetry (MTV) with acetone seeding and a pulse-burst Nd:YAG laser.
• Conducted experiments on both strut-mounted and free-flight spheres in hypersonic flow.
• Validated experimental results against simulations using a continuous Galerkin flow solver with adaptive mesh refinement.

Main Results:

• Observed reverse flow velocities between -105 and 65 m/s in the wake centerline shear layer, consistent with simulations.
• Measured average velocities of 730 m/s outside the shear layer in both experimental and simulated data.
• Estimated overall average uncertainty for strut-mounted and free-flight cases at ±4% (±35.5 m/s).

Conclusions:

• MTV provides accurate, quantitative velocity mapping in hypersonic flow wakes.
• The technique successfully captured complex flow features like reverse flow.
• MTV is a viable non-intrusive diagnostic tool for hypersonic research.