Mark Gragston
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View article: Nonseeded linewise temperature measurements by resonantly ionized photoemission thermometry in a Mach 4 Ludwieg tube
Nonseeded linewise temperature measurements by resonantly ionized photoemission thermometry in a Mach 4 Ludwieg tube Open
A one-dimensional (1D) thermometry using oxygen-tagging resonantly ionized photoelectron thermometry (O 2 RIPT) was employed to investigate thermal gradients within a Mach 4 Ludwieg tube. The Ludwieg tube is pulsed with a test duration of …
View article: Analysis of Reattachment Streaks in Hypersonic Shockwave-Boundary Layer Interactions with Upstream Roughness
Analysis of Reattachment Streaks in Hypersonic Shockwave-Boundary Layer Interactions with Upstream Roughness Open
A blunt-nosed ogive-cylinder-flare model was tested in Mach 6 flow at Texas A&M University’s ACE blowdown tunnel with swept Reynolds number and angle-of-attack (AoA). IR thermography and schlieren imaging on the windward side were taken co…
View article: Surface Heating Measurements with Temperature Sensitive Paint Films Using Fluorescent Lifetime Analysis
Surface Heating Measurements with Temperature Sensitive Paint Films Using Fluorescent Lifetime Analysis Open
Temperature sensitive paint applied to an adhesive film was used to measure surface heating utilizing a fluorescent signal lifetime analysis, in which the ratio of excitation and decay exposures was mapped to temperature via calibration. T…
View article: Multi-Point FLEET Velocimetry in a Mach 4 Ludwieg Tube using a Diffractive Optical Element
Multi-Point FLEET Velocimetry in a Mach 4 Ludwieg Tube using a Diffractive Optical Element Open
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 traditi…
View article: A Multi-Depth Focused Laser Differential Interferometer Based on Chromatic Aberration
A Multi-Depth Focused Laser Differential Interferometer Based on Chromatic Aberration Open
A modified version of a focused laser differential interferometer is demonstrated with adjacent beam pairs distributed along the optical axis. This feature is accomplished using two different wavelengths of light in the interferometer and …
View article: A Multi-Depth Focused Laser Differential Interferometer Based on Chromatic Aberration
A Multi-Depth Focused Laser Differential Interferometer Based on Chromatic Aberration Open
A modified version of a focused laser differential interferometer is demonstrated with adjacent beam pairs distributed along the optical axis. This feature is accomplished using two different wavelengths of light in the interferometer and …
View article: O<sub>2</sub> based resonantly ionized photoemission thermometry analysis of supersonic flows
O<sub>2</sub> based resonantly ionized photoemission thermometry analysis of supersonic flows Open
Characterization of the thermal gradients within supersonic and hypersonic flows is essential for understanding transition, turbulence, and aerodynamic heating. Developments in novel, impactful non-intrusive techniques are key for enabling…
View article: Effects of Surface Roughness on Shock-Wave/Turbulent Boundary-Layer Interaction at Mach 4 over a Hollow Cylinder Flare Model
Effects of Surface Roughness on Shock-Wave/Turbulent Boundary-Layer Interaction at Mach 4 over a Hollow Cylinder Flare Model Open
Although it is understood that surface roughness can impact boundary layer physics in high-speed flows, there has been little research aimed at understanding the potential impact of surface roughness on high-speed shock-wave/boundary-layer…
View article: Emissions in short-gated ns/ps/fs-LIBS for fuel-to-air ratio measurements in methane-air flames
Emissions in short-gated ns/ps/fs-LIBS for fuel-to-air ratio measurements in methane-air flames Open
A study of short-gated 10 nanosecond (ns), 100 picosecond (ps), and 100 femtosecond (fs) laser induced breakdown spectroscopy (LIBS) was conducted for fuel-to-air ratio (FAR) measurements in an atmospheric Hencken flame. The intent of the …
View article: Experimental Characterization of Two-Phase Aerated Liquid Ethanol and Jet A Spray Flames
Experimental Characterization of Two-Phase Aerated Liquid Ethanol and Jet A Spray Flames Open
This work provides an analysis of an air-assisted atomizing nebulizer’s spray characteristics and combustion behaviors via application of various diagnostics. Two-phase far-field flows and flames of liquid ethanol and practical aviation fu…
View article: Correction: Single-Shot Detection of 2-D Chemiluminescence Emissions by Compressed Hyperspectral Imaging
Correction: Single-Shot Detection of 2-D Chemiluminescence Emissions by Compressed Hyperspectral Imaging Open
Correction NoticeInstances on page 3 in which the wavelength of a red laser was given as 635 nm should read 632.8 nm.Additionally, on page 4 the wavelength given as 632 nm should read 632.8 nm to be precise.
View article: Measurement of electron density and temperature from laser-induced nitrogen plasma at elevated pressure (1–6 bar)
Measurement of electron density and temperature from laser-induced nitrogen plasma at elevated pressure (1–6 bar) Open
Laser-induced plasmas experience Stark broadening and shifts of spectral lines carrying spectral signatures of plasma properties. In this paper, we report time-resolved Stark broadening measurements of a nitrogen triplet emission line at 1…
View article: Time-Gated Single-Shot Picosecond Laser-Induced Breakdown Spectroscopy (ps-LIBS) for Equivalence-Ratio Measurements
Time-Gated Single-Shot Picosecond Laser-Induced Breakdown Spectroscopy (ps-LIBS) for Equivalence-Ratio Measurements Open
Time-gated picosecond laser-induced breakdown spectroscopy (ps-LIBS) for the determination of local equivalence ratios in atmospheric-pressure adiabatic methane–air flames is demonstrated. Traditional LIBS for equivalence-ratio measurement…
View article: Multiplexed structured image capture to increase the field of view for a single exposure
Multiplexed structured image capture to increase the field of view for a single exposure Open
In this work, we introduce multiplexed structured image capture (MUSIC) as a means to increase the field of view during a single exposure. MUSIC works by applying a unique spatial modulation pattern to the light collected from different pa…
View article: Single-shot nanosecond-resolution multiframe passive imaging by multiplexed structured image capture
Single-shot nanosecond-resolution multiframe passive imaging by multiplexed structured image capture Open
The Multiplexed Structured Image Capture (MUSIC) technique is used to demonstrate single-shot multiframe passive imaging, with a nanosecond difference between the resulting images. This technique uses modulation of light from a scene befor…
View article: Simultaneous LIBS signal and plasma density measurement for quantitative insight into signal instability at elevated pressure
Simultaneous LIBS signal and plasma density measurement for quantitative insight into signal instability at elevated pressure Open
Laser-induced breakdown spectroscopy (LIBS) evaluates the emission spectra of ions, radicals, and atoms generated from the breakdown of molecules by the incident laser; however, the LIBS signal is unstable at elevated pressures. To underst…