Hypersonic Wind-Tunnel Measurements of Boundary-Layer Transition on a Slender Cone

Casper, Katya M.; Beresh, Steven J.; Henfling, John F.; Spillers, Russell Wayne; Pruett, Brian Owen Matthew; Schneider, Steven P.

doi:10.2514/1.j054033

Cited by 83 publications

(41 citation statements)

References 36 publications

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“…They also reported that the second-mode waves, accompanied by high-frequency alternating fluid compression and expansion, produce intense aerodynamic heating in a small region. Casper et al (2016) studied boundary-layer transition on a sharp seven-degree cone in hypersonic wind tunnels at Mach five, six, eight, and fourteen. At the lowest Mach number, transition was initiated by a combination of first-and second-mode instabilities, while at higher values the boundary layer was dominated by second-mode instabilities.…”

Section: Transition In High-speed Boundary Layersmentioning

confidence: 99%

Nonlinearly most dangerous disturbance for high-speed boundary-layer transition

Jahanbakhshi

Zaki

2019

J. Fluid Mech.

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Laminar-to-turbulence transition in zero-pressure-gradient boundary layer at Mach 4.5 is studied using direct numerical simulations. For a given level of total disturbance energy, the inflow spectra was designed to correspond to the nonlinearly most dangerous condition that leads to the earliest possible transition Reynolds number. The synthesis of the inlet disturbance is formulated as a constrained optimization, where the control vector is comprised of the amplitudes and relative phases of the inlet modes; the constraints are the prescribed total energy and that the flow evolution satisfies the full nonlinear compressible Navier-Stokes equations; the cost function is the average wall friction which, once maximized, corresponds to the earliest possible transition location. An ensemble variational (EnVar) technique is developed to solve the optimization problem. EnVar updates the estimate of the control vector at the end of each iteration using the gradient of the cost function, which is computed from the outcome of an ensemble of possible solutions. Two inflow conditions are computed, each corresponding to a different level of energy, and their spectra are contrasted: the lower energy case includes two normal acoustic waves and one oblique vorticity perturbation, whereas the higher energy condition consists of oblique acoustic and vorticity waves. The focus is placed on the former case because it can not be categorized as any of the classical breakdown scenarios, while the higher energy condition undergoes a typical second-mode oblique transition. At the lower energy level, the instability wave that initiates the rapid breakdown to turbulence is not present at the inlet plane. Instead, it appears at a downstream location after a series of nonlinear interactions that spur the fastest onset of turbulence. The results from the nonlinearly most potent inflow condition are also compared to other inlet disturbances that are selected solely based on linear theory, and which all yield relatively delayed transition onset. †

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Section: Transition In High-speed Boundary Layersmentioning

confidence: 99%

Nonlinearly most dangerous disturbance for high-speed boundary-layer transition

Jahanbakhshi

Zaki

2019

J. Fluid Mech.

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“…The design and implementation of this system is discussed in detail in Ref. 17 and is therefore only briefly discussed here. Fig.…”

Section: Simulation Conditionsmentioning

confidence: 99%

“…12 The freestream conditions, blunt cone dimensions, and intermittent turbulence results were taken from a previous experimental case performed by Casper et al in Sandia's HWT-8. 17 The single roughness strip design was modified to include multiple strips in order to suppress all unstable frequencies. The design of the single roughness strip and the array is described in the following subsections.…”

Section: Roughness Designmentioning

confidence: 99%

See 1 more Smart Citation

Joint Numerical and Experimental Investigation of Roughness Effect on Hypersonic 2nd Mode Instability and Transition

Haley

Casper

Zhong

2019

AIAA Scitech 2019 Forum

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This paper details a joint numerical and experimental investigation of transition-delaying roughness. A numerical simulation was undertaken to design a surface roughness configuration that would suppress Mack's 2nd mode instability in order to maintain laminar flow over a Mach 8 hypersonic blunt cone. Following the design process the roughness configuration was implemented on a hypersonic cone test article. Multiple experimental runs at the Mach 8 condition with different Reynolds numbers were run, as well as an off-design Mach 5 condition. The roughness did appear to delay transition in the Mach 8 case as intended, but did not appear to delay transition in the Mach 5 case. Concurrently, simulations of the roughness configuration were also computed for both Mach cases utilizing the experimental conditions. Linear stability theory was applied to the simulations in order to determine their boundary layer stability characteristics. This investigation of multiple cases helps to validate the numerical code with real experimental results as well as provide physical evidence for the transition-delaying roughness phenomenon.

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“…2) The measurement of high-frequency pressure perturbations is by means of surface-mounted pressure sensors, a method that is routinely used in many experimental studies [21][22][23]. Using 1 MHz response PCB™ sensors, pressure perturbations along the model surface can be detected and analyzed in the frequency domain.…”

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confidence: 99%

Measurement of Flow Perturbation Spectra in Mach 4.5 Corner Separation Zone

et al. 2018

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Characterization of the M 4.5 flow over a flat-plate model with a 30 deg compression ramp was performed with low-enthalpy (T 0 300 K) and high-enthalpy (T 0 800-1250 K) flow conditions for a wide range of unit Reynolds numbers (Re l 4 ⋅ 10 5 − 1 ⋅ 10 7 m −1). Three measurement techniques were employed to measure the frequency spectrum of flow perturbations: a high-frequency Shack-Hartmann wavefront sensor (aerooptical method), highfrequency PCB™ pressure sensors, and a laser differential interferometer. The magnitude and frequency of flow oscillations measured by all three methods provide comprehensive and complementary results in determining spectra of gas disturbances within the flow. Of these measurement methods, the Shack-Hartmann wavefront sensor is shown to be the most suitable tool for analysis of the high-speed flow. Aerooptical measurements detect modification to the flow structure when plasma actuation is employed or when Re l is varied. In this work, flow characterization by the Shack-Hartmann sensor at individual points over the ramp has shown three flow regimes depending on the unit Reynolds number: turbulent, transitional, and laminar. At higher Re l , the freestream disturbances become strong enough to significantly affect the perturbations in the boundary-layer and the separation zone on the compression ramp. Frequency spectrum measurements during high-frequency plasma actuation (F 100 kHz) indicate amplification of the perturbations from the natural state that occur over the separation region.

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Hypersonic Wind-Tunnel Measurements of Boundary-Layer Transition on a Slender Cone

Cited by 83 publications

References 36 publications

Nonlinearly most dangerous disturbance for high-speed boundary-layer transition

Nonlinearly most dangerous disturbance for high-speed boundary-layer transition

Joint Numerical and Experimental Investigation of Roughness Effect on Hypersonic 2nd Mode Instability and Transition

Measurement of Flow Perturbation Spectra in Mach 4.5 Corner Separation Zone

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