Instability measurements of an axisymmetric, laminar separation bubble were made over a sharp cone-cylinder-flare with $12^{\circ }$ flare angle under hypersonic quiet flow. Two distinct instabilities identified: Mack's second mode (which peaked between 190 and 290 kHz) the shear-layer instability in same frequency band as first (observed 50 150 kHz). Both measured surface pressure sensors captured high-speed schlieren. Linear stability analysis results agreed well these terms both peak...

Compression corners are commonly present along aircraft, such as at control surfaces, and can cause shock/boundary-layer interactions when the vehicle moves supersonic or hypersonic speeds. By generating a separation bubble corner, shear layer is in flow, which potentially amplify instabilities, leading to boundary-layer transition downstream of reattachment. We show, through experiments conducted under low-disturbance Mach-6 amplification shear-layer instability by comparing measurements...

An axisymmetric sharp cone-cylinder-flare model was tested in the Boeing/AFOSR Mach 6 Quiet Tunnel (BAM6QT) at 0.0-degree angle of attack. Heat transfer and surface-pressure-fluctuation measurements were made both conventional noise quiet flow. Off-the-surface density fluctuation with focused laser differential interferometry (FLDI) Second mode fluctuations as well a different type travelling wave observed downstream PCB, Kulite, FLDI measurements. These waves are not predicted by linear...

The effect of turbulent wind-tunnel-wall boundary layers on density change measurements obtained with focused laser differential interferometry (FLDI) was studied using a detailed direct numerical simulation (DNS) the wall from Boeing/AFOSR Mach-6 Quiet Tunnel run in its noisy configuration. DNS probed an FLDI model that is capable reading three-dimensional time-varying fields and computing response. Simulated smooth boundary-layer root-mean-square (RMS) profile relative to true values by...

A focused laser differential interferometer (FLDI) simulation was used to study the sensitivity of FLDI technique a variety factors. The model takes in series density fields and computes beam phase difference response those fields. For pure sinusoidal signals finite width, frequency found have no effect on computed below photodetector threshold. signal wavelength, however, has direct correlation with amplitude; peak amplitude achieved wavelength double separation when measured at focal...

View Video Presentation: https://doi.org/10.2514/6.2023-2438.vid A self-aligned focusing schlieren (SAFS) apparatus based on a recently published design is implemented for the purpose of making near-planar density gradient measurements hypersonic boundary layers. At working distance one meter, current SAFS setup shown to be capable depths focus order 1-10 mm while also achieving framerates in 100 kHz 1+ MHz range at exposures as short 20 ns. These qualities are achieved remaining resistant...

A unique focused laser differential interferometry (FLDI) configuration designed to work with contoured windows was developed for use the Boeing/U.S. Air Force Office of Scientific Research Mach 6 Quiet Tunnel (BAM6QT) at Purdue University. The modified FLDI uses cylindrical lenses help shape beam profile together curved windows. design informed by a ray-tracing simulation apparatus. spatial sensitivity BAM6QT tested using density-fluctuation measurements small-diameter air jet and compared...

Computations are performed to investigate the convective and global boundary-layer instabilities over a sharp cone–cylinder–flare model at zero-degree angle of attack. The geometry flow conditions selected match experiments conducted in Boeing/AFOSR Mach 6 Quiet Tunnel Purdue University. consists nominally 5 deg half-angle cone, followed by cylindrical segment, then 10 flare. Additionally, flare half angles equal 8 12 nosetip radii 0.1, 1, mm studied. An axisymmetric separation bubble is...

Base flow computation and stability analysis were conducted for hypersonic over a cone-cylinder-flare (CCF) geometry conditions that correspond to the experimental runs carried out in three wind tunnels. Owing presence of an attached boundary layer, separation bubble induced by shock-boundary layer interaction, reattachment region, chosen configuration is physically rich. The complexity this flowfield encompasses combination convective instabilities developing on cone, global bubble,...

Several experimental campaigns have been conducted across a number of Mach-6 facilities on the hypersonic flow around cone-cylinder-flare (CCF) geometry with 5$^{\circ}$ half-angle cone and 12$^{\circ}$ flare. These experiments were as part NATO STO Research Task Group AVT-346, which is focused predicting boundary-layer transition complex geometries. This extended abstract describes details CCF model wind tunnel in France United States where this was tested. The final paper will include...

View Video Presentation: https://doi.org/10.2514/6.2023-0098.vid A series of experiments were performed in the Air Force Research Laboratory Mach-6 Ludwieg Tube using a variable tip-curvature model for purpose studying influence leading edge spanwise curvature on downstream boundary layer distortion and transition trends. total five different profiles examined at freestream unit Reynolds numbers ranging from approximately 2.2-24.1*10^6 m^-1. Boundary disturbances measured high speed, z-type...

Experimental campaigns were conducted across three Mach 6 facilities on the hypersonic flow around a cone-cylinder-flare (CCF) geometry as part of NATO STO Research Task Group AVT-346. Two conventional (AFRL M6LT and ONERA R2Ch) one quiet tunnel (Purdue BAM6QT) used to test same study instabilities in both boundary layer shear above axisymmetric separation bubble. nose tip radii (one nominally sharp blunt with 5 mm radius) tested. For case, there was excellent agreement between measurements...

Baseflow computation and stability analysis were conducted for hypersonic flow over a cone-cylinder-flare (CCF) geometry conditions that correspond to the experimental runs carried out in three wind tunnels. Owing presence of an attached boundary layer, separation bubble induced by shock–boundary-layer interaction, reattachment region, chosen configuration is physically rich. The complexity this flowfield encompasses combination convective instabilities developing on cone, global bubble,...

A focused laser differential interferometer (FLDI) was developed for use with the Boeing/AFOSR Mach 6 Quiet Tunnel (BAM6QT) at Purdue University. To test initial FLDI, density-fluctuation measurements were made in a shock tube. The modified FLDI design then to work contoured windows of tunnel, and its spatial sensitivity tested using small-diameter air jet. Second mode fluctuation on 7 degree half-angle cone 0 degrees angle attack. Both conventional-noise quiet-flow good agreement between...

View Video Presentation: https://doi.org/10.2514/6.2023-0869.vid The reconstruction of globally-consistent hypersonic boundary layer disturbance modes from experimental schlieren measurements is demonstrated via the implementation a phase-consistent spectral proper orthogonal decomposition (pcSPOD) scheme. pcSPOD technique used to process high-speed z-type and focusing images layers over both sharp blunt tip ogive-cylinder in Air Force Research Laboratory Mach-6 Ludwieg Tube. resulting mode...

View Video Presentation: https://doi.org/10.2514/6.2023-4253.vid Simultaneous density-fluctuation measurements were made using a linear array focused laser differential interferometer (LA-FLDI) over 7-deg sharp cone in Mach-6 flow. Second-mode fluctuations measured and showed to vary amplitude with height above the surface Reynolds number sweep captured transition onset. As increased, peak fluctuation decreased due thinning of boundary layer. The computed density eigenfunction was compared...

As part of NATO STO AVT-346 “Predicting Hypersonic Boundary-Layer Transition on Complex Geometries,” coordinated experimental and computational studies were conducted the ROTEX-T, a cone-flare geometry used in successful flight-test experiment. At as-flown conditions, separation bubble existed at compression corner. Separation, reattachment, multifaceted linear instability paths leading this to transition turbulence are challenging predict, but have significant impact surface pressure heat...

The stability of hypersonic boundary-layer over an axisymmetric cone-cylinder-flare config- uration at Mach 6 and zero degree angle attack is investigated for different Reynolds numbers. shape has been designed wind tunnel test experiments with two main goals: keep attached all along the object investigate effects pressure gradients, flow expansion recompression without separation, on stability. After a thorough study aerodynamic obtained in fully laminar condi- tions, linear theory (LST)...

View Video Presentation: https://doi.org/10.2514/6.2023-1245.vid A blunt cone-cylinder-flare model was tested at the AFRL Mach-6 Ludwieg Tube 0-degree angle of attack. Surface-pressure fluctuation measurements, high-speed schlieren images, and surface-heat-transfer measurements were taken to study instability transition as related an axisymmetric separation bubble downstream a nosetip. Two nosetip radii tested, 1 mm 5 mm. Only minimal streaks present in heat transfer results reattachment,...

A direct numerical simulation (DNS) of a transitional hypersonic boundary layer about an axisymmetric model was conducted and probed by simulated focused laser differential interferometer (FLDI). The FLDI is capable simulating time-varying signals computing the expected measurement. measurements density difference were found to underestimate off-surface location peak fluctuations relative "true" directly extracted from DNS. An investigation into where discrepancy originates, it determined be...