Experimental Study of Second-Mode Instabilities on a 7-Degree Cone at Mach 6

Rufer, Shann J.; Berridge, Dennis C.

doi:10.2514/6.2011-3877

Cited by 13 publications

(3 citation statements)

References 24 publications

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“…[1][2][3][4][5][6][7][8][9][10][11][12][13] The elevated freestream disturbance levels in conventional (i.e., noisy) high-speed wind tunnels usually result in an earlier onset of transition relative to that in a flight environment or in a quiet tunnel. Yet, the conventional facilities continue to be used for transition sensitive measurements because of the size and Reynolds number limitations of existing quiet facilities and the prohibitive cost of flight tests.…”

Section: Introductionmentioning

confidence: 99%

Numerical Study of Pressure Fluctuations due to a Mach 6 Turbulent Boundary Layer

Duan

Choudhari

2013

51st AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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Direct numerical simulations (DNS) are used to examine the pressure fluctuations generated by a Mach 6 turbulent boundary layer with nominal freestream Mach number of 6 and Reynolds number of Reτ ≈ 464. The emphasis is on comparing the primarily vortical pressure signal at the wall with the acoustic freestream signal under higher Mach number conditions. Moreover, the Mach-number dependence of pressure signals is demonstrated by comparing the current results with those of a supersonic boundary layer at Mach 2.5 and Reτ ≈ 510. It is found that the freestream pressure intensity exhibits a strong Mach number dependence, irrespective of whether it is normalized by the mean wall shear stress or by the mean pressure, with the normalized fluctuation amplitude being significantly larger for the Mach 6 case. Spectral analysis shows that both the wall and freestream pressure fluctuations of the Mach 6 boundary layer have enhanced energy content at high frequencies, with the peak of the premultiplied frequency spectrum of freestream pressure fluctuations being at a frequency of ωδ/U∞ ≈ 3.1, which is more than twice the corresponding frequency in the Mach 2.5 case. The space-time correlations indicate that the pressure-carrying eddies for the higher Mach number case are of smaller size, less elongated in the spanwise direction, and convect with higher convection speeds relative to the Mach 2.5 case. The demonstrated Mach-number dependence of the pressure field, including radiation intensity, directionality, and convection speed, is consistent with the trend exhibited in experimental data and can be qualitatively explained by the notion of 'eddy Mach wave' radiation. NomenclatureC p heat capacity at constant pressure, J/(K·kg) C pp Space-time correlation coefficient of the pressure field, dimensionless C v heat capacity at constant volume, J/(K·kg)

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Section: Introductionmentioning

confidence: 99%

Numerical Study of Pressure Fluctuations due to a Mach 6 Turbulent Boundary Layer

Duan

Choudhari

2013

51st AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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“…The diameter of the sensors is 3.18 mm, however the quadratic active area is smaller (0.762 * 0.762 mm²), see e.g. Rufer and Berridge [15]. The signal conditioning and power supply was made by two PCB instruments M482A22.…”

Section: Instrumentationmentioning

confidence: 99%

Instability Modes in Boundary Layers of an Inclined Cone at Mach 6

Muñoz

Heitmann

Radespiel

2012

42nd AIAA Fluid Dynamics Conference and Exhibit

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The stability of a three-dimensional hypersonic boundary layer is experimentally investigated for a 7° half angle cone at an angle of attack of 6°. The measurements were carried out in the Hypersonic Ludwieg tube Braunschweig at a Mach number of 6. Surface mounted pressure sensors were used to capture information about the spatial extension, frequency content and wave structure of first and second mode instabilities. Infrared images were used to identify the location, direction and growth of stationary cross flow instabilities. In the present work the behavior of these disturbances at noisy wind tunnel conditions is described for different locations along the cone and Reynolds numbers. Nomenclature 2D= Two dimensional 3D = Three dimensional DFT = Discrete Fourier transform HLB = Hypersonic Ludwig tube Braunschweig IR = Infrared PSD = Power spectral density Symbols dt = time step n = distance along the surface of the cone perpendicular to s s = distance along the surface of the cone parallel to the local streamlines x = distance along the principal axis of the cone z = distance along the surface of the cone perpendicular to the principal axis of the cone θ = azimuthal angle around the model main axis

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“…33) has also proven to be quite robust, capable of surviving in many hypersonic tunnels, with a low incidence of broken sensors. [34][35][36][37][38][39] These qualities make attempting instability measurements feasible, even in many of the large tunnels used to test vehicles.…”

Section: Efforts Towards Calibration Of Pcb-132 Sensors and Consmentioning

confidence: 99%

Boundary-Layer Instability Measurements in a Mach-6 Quiet Tunnel

Berridge

Ward

Luersen

et al. 2012

42nd AIAA Fluid Dynamics Conference and Exhibit

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Several experiments have been performed in the Boeing/AFOSR Mach-6 Quiet Tunnel at Purdue University. A 7• half angle cone at 6• angle of attack with temperature-sensitive paint (TSP) and PCB pressure transducers was tested under quiet flow. The stationary crossflow vortices appear to break down to turbulence near the lee ray for sufficiently high Reynolds numbers. Attempts to use roughness elements to control the spacing of hot streaks on a flared cone in quiet flow did not succeed. Roughness was observed to damp the second-mode waves in areas influenced by the roughness, and wide roughness spacing allowed hot streaks to form between the roughness elements. A forward-facing cavity was used for proof-of-concept studies for a laser perturber. The lowest density at which the freestream laser perturbations could be detected was 1.07 × 10 −2 kg/m 3 . Experiments were conducted to determine the transition characteristics of a streamwise corner flow at hypersonic velocities. Quiet flow resulted in a delayed onset of hot streak spreading. Under low Reynolds number flow hot streak spreading did not occur along the model. A new shock tube has been built at Purdue. The shock tube is designed to create weak shocks suitable for calibrating sensors, particularly PCB-132 sensors. PCB-132 measurements in another shock tube show the shock response and a linear calibration over a moderate pressure range. Nomenclature

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Experimental Study of Second-Mode Instabilities on a 7-Degree Cone at Mach 6

Cited by 13 publications

References 24 publications

Numerical Study of Pressure Fluctuations due to a Mach 6 Turbulent Boundary Layer

Numerical Study of Pressure Fluctuations due to a Mach 6 Turbulent Boundary Layer

Instability Modes in Boundary Layers of an Inclined Cone at Mach 6

Boundary-Layer Instability Measurements in a Mach-6 Quiet Tunnel

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