Nitric-oxide planar laser-induced fluorescence was used to perform velocity measurements in hypersonic flows by generatingmultiple tagged lines thatfluoresce as they convect downstream.Determination of axial velocitywasmade application a cross-correlation analysis the horizontal shift individual lines. A single interline, progressive scan-intensified charge-coupled device camera obtain two sequential images nitricoxide molecules that had been laser. The allowed for submicrosecond acquisition...

A Nomarski polarizing prism has been used in conjunction with a focused laser differential interferometer to measure the phase velocity of density disturbance at sampling frequencies ≥10MHz. Use this enables simultaneous measurement disturbances two closely spaced points that can be arbitrarily oriented about instrument's optical axis. The orientation is prescribed by rotating Since all four beams (one beam pair each point) propagate parallel one another within test volume, any bias imparted...

A multi-point focused laser differential interferometer (FLDI) has been developed to measure density fluctuations at 16 points along a line. pair of cylindrical lenses on the transmitter side conventional single-point FLDI instrument form two closely spaced ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>≤</mml:mo> </mml:mrow> <mml:mn>200</mml:mn> <mml:mspace width="thinmathspace"/> <mml:mtext>µ</mml:mtext> <mml:mi...

Nitric oxide (NO) planar laser-induced fluorescence (PLIF) has been use to investigate the hypersonic flow over a flat plate with and without 2-mm (0.08-in) radius hemispherical trip. In absence of trip, for all angles attack two different Reynolds numbers, was observed be laminar mostly steady. Boundary layer thicknesses based on PLIF intensity were measured compared CFD computation, showing agreement. The boundary thickness remained constant while NO flowrate varied by factor 3, indicating...

A novel, to the best of our knowledge, compact, self-aligned focusing schlieren system is presented that eliminates need for a separate source grid and cutoff grid. single element serves both generate projected onto retroreflective background act as reflected light. This made possible by manipulating polarization light through system. The use only create perfectly matched scaled grid, removes align grids each other. sensitivity density objects adjustable with polarizing prism. Images...

The implementation of a self-aligned focusing schlieren (SAFS) system at two cryogenic wind tunnels NASA Langley Research Center is discussed. Risk-reduction testing the SAFS was first performed 0.3-M Transonic Cryogenic Tunnel to evaluate system's operation in small-scale characteristic facility. Testing conducted with three models: three-quarter span 25.4-mm-diameter cylinder, semi-span 65A006 tapered unswept airfoil, and full-span SC(3)-0712 airfoil. cylinder revealed highly dynamic shock...

A method is presented to acquire self-aligned focusing schlieren (SAFS) images when the optical axis of instrument positioned at a non-normal incidence angle background plane on which grid pattern projected, or measurement gradients in density are visualized, both. This accomplished by applying Scheimpflug principle and properly orienting planes physical image sensor reside within so that focused can be captured. Focused from laboratory tests, where were separately then simultaneously...

In two separate test entries, advanced laser-based instrumentation has been developed and applied to visualize the hypersonic flow over cylindrical protrusions on a flat plate. Upstream of these trips, trace quantities nitric oxide (NO) were seeded into boundary layer. The protuberances sized force laminar-to-turbulent layer transition. first test, 10-Hz planar laser-induced fluorescence (NO PLIF) visualization system was used provide wide-field-of-view, high-resolution images flowfield. had...

Numerical simulations of the gas-seeding strategies required for planar laser-induced fluorescence in a Mach 10 (approximately 8.2 postshock) airflow were performed. The work was performed to understand and quantify adverse effects associated with gas seeding assess various types seed that could potentially be used future experiments. In prior experiments, NO NO2 injected through slot near leading edge flat-plate wedge model NASA Langley Research Center's 31 in. air tunnel facility. this...

Using a recently developed Schlieren-based shock-detection algorithm, experiments were conducted in the 20 in. Mach 6 wind tunnel facility at NASA Langley Research Center to investigate unsteadiness turbulent and transitional shock-wave/boundary-layer interactions 4.2 edge conditions over range of Reynolds numbers between . Separation shock was found exhibit probability density functions with 50% greater streamwise than interactions, mean location forward lambda-shock position increase by...

Shock-wave/boundary-layer interactions (SWBLIs) are critical phenomena in the design of high-speed vehicles as they exhibit inherent unsteadiness that can damage airframes and lead to engine unstart. This paper presents a novel characterization unsteady dynamics cylinder-induced SWBLIs at Reynolds numbers using proper orthogonal decomposition (POD) dynamic mode (DMD). Data sets analyzed this were obtained from experiments conducted NASA Langley Research Center's 20-Inch Mach 6 blowdown wind...

View Video Presentation: https://doi.org/10.2514/6.2022-0560.vid A novel compact, inherently self-aligned focusing schlieren system is presented for use in experiments that require flow visualization. Unlike existing systems a separate, and precisely aligned, source grid cutoff to achieve sensitivity density gradients, this projects an image of physical element onto background then reimages projection back the thereby achieving self alignment. Further, unlike where physically translated...

Planar laser-induced fluorescence of naturally occurring nitric oxide has been used to provide insight into baseline flow conditions the Hypersonic Materials Environmental Test System 400 kW arc-heated wind tunnel at NASA Langley Research Center via radial and axial velocity measurements instantaneous flow-visualization images. This represents both first flow-tagging application nitric-oxide planar visualization in an arcjet facility. Results are presented selected facility run conditions,...

Nitric oxide planar laser-induced fluorescence measurements have been performed in a small-scale scramjet combustor at the University of Virginia Aerospace Research Laboratory nominal simulated Mach 5 flight. A mixture nitric and nitrogen was injected upstream end inlet isolator as surrogate for ethylene fuel, mixing this fuel simulant studied with without shock train. The train produced by an air throttle, which blockage effects combustion downstream cavity flameholder. signal imaged plane...

View Video Presentation: https://doi.org/10.2514/6.2022-1796.vid The continuous development and advancement of multi-point line focused laser differential interferometry (FLDI) instruments requires larger numbers acquisition channels to make more finely spatially resolved measurements high-frequency flow fluctuations. No current off-the-shelf system exists for these FLDI measurements, so a single unified consisting linear array photodiode, required electronics, data has been developed...

A colinear focused laser differential interferometer (FLDI) and self-aligned focusing schlieren (SAFS) system has been assembled tested in the laboratory, using a turbulent jet of compressed air issuing from small needle nozzle to provide high frequency density object. Measurements verified that coupling SAFS onto optical axis FLDI had negligible influence on system's data, including tests assessed inclusion dichroic mirrors, mirror reflection angle, positioning relative Wollaston prisms...

The combination of the background oriented schlieren (BOS) technique with unique imaging capabilities a plenoptic camera, termed BOS, is introduced as new addition to family techniques. Compared conventional single camera BOS capable sampling multiple lines-of-sight simultaneously. Displacements from each line-of-sight are collectively used build four-dimensional displacement field, which vector function structured similarly original light field captured in raw image. render focused images,...

Femtosecond laser electronic excitation tagging (FLEET) is an optical measurement technique that permits quantitative velocimetry of unseeded air or nitrogen using a single and camera. In this paper, we seek to determine the fundamental precision FLEET high-speed complementary metal-oxide semiconductor (CMOS) cameras. Also, compare performance several different CMOS camera systems for acquiring data in free-jet flows. The was defined as standard deviation set hundred single-shot velocity...