The recent progress in high-speed (≥100kHz) laser diagnostics for hypersonic flows is reviewed. Owing to the ultrahigh flow speed, a frequency of 100 kHz or higher required diagnostics. Here, two main diagnostic techniques are discussed: focused differential interferometry (FLDI) and pulse-burst laser-based Single- multiple-point FLDI measurements have been widely applied velocity density fluctuation measurements. diagnostics, including 2D visualization, also discussed.

Nanosecond laser-induced breakdown spectroscopy (ns-LIBS) is employed for quantitative local fuel-air (F/A) ratio (i.e., of actual fuel-to-oxidizer mass over at stoichiometry, measurements in well-characterized methane-air flames pressures 1-11 bar). We selected nitrogen and hydrogen atomic-emission lines 568 nm 656 nm, respectively, to establish a correlation between the line intensities F/A ratio. have investigated effects laser-pulse energy, camera gate delay, pressure on sensitivity,...

In this Letter, a modification of the well-known focused-laser differential interferometer (FLDI) is demonstrated, with primary focus being increasing number probed locations efficiently. To generate multiple beams in FLDI system, diffractive optical element used. This approach significantly more cost-effective and easier to implement than current generating beam pairs using series Wollaston prisms. The measurements shown here utilize 1D linear array points, ability 2D demonstrated two...

Temperature-sensitive paint (TSP) films are developed via application of the TSP to 0.11-mm-thick polyvinyl-chloride with an adhesive backing. This approach allows be quickly replaced on models if surface damage occurs during testing, which is common in impulse facilities used create hypersonic flow conditions. work demonstrates that quantitative calibration signal still possible and only top coat necessary for thermally insulative films, aids simplifying heat flux calculations. The film...

A simple method for correcting the motion blur effects in molecular tagging velocimetry (MTV) data is developed and evaluated synthetic MTV generated from theoretical laminar turbulent boundary-layer profiles. The analysis shows that correction capable of scenarios fast slow emission decay. An analytical solution model equations converges to gate-centered timing approach limit no blurring two common gating are also explored, it shown really only needed scenario unequal exposure times....

Two-dimensional (2D) Raman scattering at 10 kHz in non-reacting flow mixtures is demonstrated by employing a burst-mode laser with long-duration pulse of about 70 ns and energy 750 mJ 532 nm. To avoid optical breakdown, the width was varied range 10-1000 ns. The effects shape, energy, harmonic conversion on 2D measurements are also studied. applications high-speed, single-shot, imaging CH4 H2 jets N2 elevated pressures demonstrated. In addition, scalar dissipation rate 20 bar determined,...

Quasi-random distributed roughness topologies were produced to transition the boundary layer over an axisymmetric tangent ogive nosecone in hypersonic flow. Surface was accomplished by applying a cylindrical 2D Fourier series triangulated surface of nosetip manner that resembles sand grit roughness. In total, one smooth tip and three rough tips with varying heights 3D-printed examine their effectiveness at transition. The models assessed Infrared (IR) Thermography Focused Laser Differential...

The boundary layer on a sharp-tip, partially flared, actively cooled cone with discrete roughness elements has been studied in quiet Mach 6 wind tunnel using linear array–focused laser differential interferometry (LA-FLDI). conditions were varied by sweeping the unit Reynolds number of flow from to and wall temperature was set one two setting coolant setpoint 293.2 or 253.2 K. spectral content showed presence second-mode instability, which is dominant its harmonics across sweep. A novel...

A diffractive optical element was paired with femtosecond laser electronic excitation tagging (FLEET) velocimetry and used to probe multiple locations in a high-speed wind tunnel. Two configurations were explored, one that uses the traditional method of viewing from perspective orthogonal beam axis another parallel axis. In latter, FLEET emissions are viewed as points can allow for measurements wall normal fashion without needing impinge upon surface. The demonstrated Mach 4 Ludwieg tube,...

Temperature-sensitive paint and infrared thermography have been used for transition surface heating measurements in hypersonic wind tunnel facilities. A blowdown capable of variable Reynolds numbers was operated at Mach 6 over a number range approximately 2-9 million per meter, boundary layer induced on NASA 91-6 flared cone model. Thermal effects associated with the were recorded simultaneously diagnostic techniques. The data calibration response, technique compared favorably thermographic...

This work describes the use of a laser-induced breakdown spectroscopy (LIBS) system to conduct macroscopic elemental mapping uranium and iron on exterior surface interior center cross-section surrogate nuclear debris for first time. The results suggest that similar LIBS systems could be packaged as an effective instrument screening samples during collection activities in field or process control measurements production surrogates. technique focuses mitigation chemical physical matrix effects...

Focused laser differential interferometry (FLDI) is used to measure a well-characterized, 17 kHz screech tone emitted from an underexpanded Mach 1.5 jet. Measurements are made at numerous spatial locations in and around the jet flow-field, where intrusive diagnostics would otherwise influence flow-field. Results FLDI measurements shown agree with microphones analyses of high-speed schlieren. The agreement demonstrate valid accurate technique for measuring tones flow-fields, furthermore that...

In this work, the capabilities of traditional focused-laser differential interferometry (FLDI) technique are expanded in an efficient manner to allow for simultaneous probing several spatial locations using a diffractive optical element. The technique, called linear array- (LA-FLDI), is demonstrated measurements well-characterized screech tones under-expanded Mach 1.5 jet and UTSI 4 Ludwieg tube turbulent floor boundary layer. A measurement convective velocity layer also made signal...

View Video Presentation: https://doi.org/10.2514/6.2023-1457.vid A new hypersonic Ludwieg tube has been constructed at the University of Tennessee Space Institute (UTSI) to support increased research activities related vehicle development. The 45.72 cm by (18" 18") nozzle exit dimension allows for large models be tested and development flow diagnostic techniques on a scale similar high-speed test evaluation (T&E) facilities AEDC. description facility design initial characterization is...