Cross-Flow Instability Experiments on a Swept Fin-Cone with Variable Nose Bluntness in Mach 6 Flow

Middlebrooks, John B.; Farnan, Emma; Juliano, Thomas J.; Matlis, Eric; Corke, Thomas; Peck, Madeline M.; Mullen, Daniel; Reed, Helen L.; Semper, Michael

doi:10.2514/6.2022-0598

Cited by 5 publications

(10 citation statements)

References 21 publications

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“…The bullet head was drawn from the actual bullet in the middle, which was changed from the round-nosed tip to a blunt-nosed tip [ 37 ], as shown on the left and right of Figure 1 , respectively. This tip parameter was neglected since there was no air resistance environment in the simulation.…”

Section: Methodsmentioning

confidence: 99%

Numerical Simulation Study on Relationship between the Fracture Mechanisms and Residual Membrane Stresses of Metallic Material

Miskon

Zaidi

Ahmad

et al. 2022

JFB

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The distribution and dissipation energies in fracture mechanisms were a critical challenge to derive, especially for this ultra-thin sample. The membrane failure, which is the end of the fracture mechanisms, is a result of the cone wave reflections from the backend membrane boundaries. These reflections delay the failure processes due to the shock impacts. To compare these results with the experimental work, a numerical simulation was conducted for these processes. The cylinder-shaped rigid projectile was impacted using a frictionless Lagrange solver. The target was a cartridge brass circle plate clamped at its perimeter, and its zone was refined to a ten-times higher meshing density for better analysis. The erosion and cut-off controls involved a zero-gap interaction condition and an instantaneous geometric erosion strain of 200%. Due to the maximum projectile velocity of 382 m/s having the slowest perforation, the target thickness was found to be 5.5 mm. The fracture mechanism phenomena, such as tensile, compressive, through-thickness, and growth in-plane delamination, propagating delamination, and local punch shear waves were observed. After deducting tensile and flexural strengths from the last experiment, a total residual membrane stress of 650 MPa was found. This result indicated a relationship between the fracture mechanisms and residual membrane stresses of metallic material.

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Section: Methodsmentioning

confidence: 99%

Numerical Simulation Study on Relationship between the Fracture Mechanisms and Residual Membrane Stresses of Metallic Material

Miskon

Zaidi

Ahmad

et al. 2022

JFB

View full text Add to dashboard Cite

show abstract

“…The geometry used in this work is based off of the model used in experiments by Middlebrooks et al (2022). The body is a straight cone with a half-angle of 7 • and a circular nose tip with a radius of 5.323 mm.…”

Section: Geometry and Laminar Base Flowmentioning

confidence: 99%

“…The fin alone uses 354 grid points in the azimuthal direction. The convergence of the base flows was demonstrated in Middlebrooks et al (2022) by examining the sensitivity of LPSE results to the base-flow grid density. In the one non-zero-yaw case, the…”

Section: Geometry and Laminar Base Flowmentioning

confidence: 99%

“…The stability plane is oriented perpendicular to the leading edge and spanwise gradients are neglected. Analysis in Middlebrooks et al (2022) demonstrates this is an acceptable assumption because the spanwise pressure gradient (banded between −0.5 and 0.5 kPa m −1 ) is small compared with the streamwise pressure gradient (which has a maximum favourable gradient of ∼1050 kPa m −1 , and remains at least an order of magnitude larger than the spanwise gradient throughout the streamwise domain). Further evidence is provided in Middlebrooks et al (2022) by comparing the LPSE results computed at 12 different spanwise stations.…”

Section: Harmonic Linearized Navier-stokes Equationsmentioning

confidence: 99%

“…Accompanying computations using the linear parabolized stability equations (LPSE) indicated that, in the Reynolds-number range examined, the cross-flow instability on the fin was insignificant compared with the second mode (Mullen et al 2019). A second set of experiments, conducted in the Air Force's Mach 6 Ludwieg Tube, focused on identifying transition near the leading edge (Middlebrooks et al 2022). Using surface heat-flux measurements, heat-flux striations and a transition front were identified at the highest unit Reynolds number tested (Re = 22 × 10 6 m −1 ).…”

Section: Introductionmentioning

confidence: 99%

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Boundary-layer instability on a highly swept fin on a cone at Mach 6

Peck,

Groot,

Reed

2024

J. Fluid Mech.

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The growth and characteristics of linear, oblique instabilities on a highly swept fin on a straight cone in Mach 6 flow are examined. Large streamwise pressure gradients cause doubly inflected cross-flow profiles and reversed flow near the wall, which necessitates using the harmonic linearized Navier–Stokes equations. The cross-flow instability is responsible for the most-amplified disturbances, however, not all disturbances show typical cross-flow characteristics. Distinct differences in perturbation structure are shown between small ( $\sim$ 3–5 mm) and large ( $\sim$ 10 mm) wavelength disturbances at the unit Reynolds number $Re' = 11 \times 10^6$ m $^{-1}$ . As a result, amplification measurements based solely on wall quantities bias a most-amplified disturbance assessment towards larger wavelengths and lower frequencies than would otherwise be determined by an off-wall total-energy approach. A spatial-amplification energy-budget analysis demonstrates (i) that wall-normal Reynolds-flux terms dictate the local growth rate, despite other terms having a locally larger magnitude and (ii) that the Reynolds-stress terms are responsible for large-wavelength disturbances propagating closer to the wall compared with small-wavelength disturbances. Additionally, the effect of free-stream unit Reynolds number and small yaw angles on the perturbation amplification and energy budget is considered. At a higher Reynolds number ( $Re' = 22 \times 10^6$ m $^{-1}$ ), the most-amplified wavelength shrinks. Perturbations do not behave self-similarly in the thinner boundary layer, and the shift in most-amplified wavelength is due to decreased dissipation relative to the lower-Reynolds-number case. Small yaw angles produce a streamwise shift in the boundary layer and disturbance amplification. The yaw results quantify a potential uncertainty source in experiments and flight.

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Cross-flow instability on a swept-fin cone at Mach 6: characteristics and control

Middlebrooks,

Corke,

Matlis

et al. 2024

J. Fluid Mech.

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Experiments were performed to document the complex flow field around and over a $70^{\circ }$ swept fin mounted on a $7^{\circ }$ half-angle right-circular cone in a Mach 6 free-stream. Of particular interest is the turbulent transition of the boundary layer over the swept fin, which is expected to be dominated by a cross-flow instability. Stationary features in the surface temperature distribution over the fin are documented using infrared thermal imaging. These were processed further to determine average spatial Stanton number distributions over the fin. Wavelet analysis of the Stanton number distributions revealed stationary patterns with wavelengths near the fin leading edge that were consistent with linear theory predictions of stationary cross-flow modes. Further from the leading edge, the wavelength of the stationary patterns was observed to increase prior to turbulence onset. Based on these observations, specially designed arrays of discrete roughness elements (DREs) were investigated as a means of delaying turbulence transition with the objective of reducing surface heat flux on the swept fin. The DRE designs followed our previous approach used for cross-flow transition control (Corke et al., J. Fluid Mech., vol. 856, issue 10, 2018, pp. 822–849; Arndt et al., J. Fluid Mech., vol. 887, 2020, A30). These focused on either the shorter wavelengths near the leading edge, or the longer wavelengths that developed near turbulence onset. With regard to delaying transition and reducing the surface heat flux, the DREs that focused on the larger wavelengths of stationary modes were most effective. The fin included an array of pressure sensors that were used to document travelling disturbances that could include those associated with travelling cross-flow modes. Phase analysis of the pressure fluctuation time series was used to determine the wavelength, wave angle and phase speed that were consistent with the travelling cross-flow modes. Cross-bicoherence analysis between the stationary and travelling disturbances indicates a nonlinear phase locking that can account for the development of the longer-wavelength stationary features in the surface heat flux, presumed to be due to stationary cross-flow modes, prior to turbulence onset.

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Cross-Flow Instability Experiments on a Swept Fin-Cone with Variable Nose Bluntness in Mach 6 Flow

Cited by 5 publications

References 21 publications

Numerical Simulation Study on Relationship between the Fracture Mechanisms and Residual Membrane Stresses of Metallic Material

Numerical Simulation Study on Relationship between the Fracture Mechanisms and Residual Membrane Stresses of Metallic Material

Boundary-layer instability on a highly swept fin on a cone at Mach 6

Cross-flow instability on a swept-fin cone at Mach 6: characteristics and control

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