VITA measurements of transition in transitional hypersonic boundary layer flows

Chokani, Ndaona

doi:10.1007/s00348-004-0923-y

Cited by 4 publications

(4 citation statements)

References 19 publications

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“…This second mode instability precedes the final breakdown of the hypersonic laminar boundary layer and transition to turbulence. [2] …”

Section: Resultsmentioning

confidence: 99%

“…These increases have significant impact on the performance control, fuel consumption, structural design and thermal protection system of hypersonic vehicles because the aerodynamics performances are very sensitive to the changes in wall thermal and aerodynamic loadings that accompany laminar-turbulent transition. Therefore, understanding the laminar-turbulent transition mechanism and predicting the transition location accurately are the keys to achieve the desired aerodynamic performances [2]. Unlike the case of subsonic flow, the mechanisms underlying the laminar-turbulence transition in hypersonic flow still remain poorly understood both in experiment and theory [3].…”

Section: Introductionmentioning

confidence: 99%

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Second mode unstable disturbance measurement of hypersonic boundary layer on cone by wavelet transform

2011

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Experimental investigation of hypersonic boundary layer instability on a cone is performed at Mach number 6 in a hypersonic wind tunnel. Time series signals of instantaneous fluctuating surface-thermal-flux are measured by Pt-thin-film thermocouple temperature sensors mounted at 28 stations on the cone surface in the streamwise direction to investigate the development of the unstable disturbance. Wavelet transform is employed as a mathematical tool to obtain the multi-scale characteristics of fluctuating surfacethermal-flux both in the temporal and spectrum space. The conditional sampling algorithm using wavelet coefficient as an index is put forward to extract the unstable disturbance waveform from the fluctuating surface-thermal-flux signals. The generic waveform for the second mode unstable disturbance is obtained by a phase-averaging technique. The development of the unstable disturbance in the streamwise direction is assessed both in the temporal and spectrum space. Our study shows that the local unstable disturbance detection method based on wavelet transformation offers an alternative powerful tool in studying the hypersonic unstable mode of laminar-turbulent transition. It is demonstrated that, at hypersonic speeds, the dominant flow instability is the second mode, which governs the course of laminar-turbulent transition of sharp cone boundary layer.

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“…This second mode instability precedes the final breakdown of the hypersonic laminar boundary layer and transition to turbulence. [2] …”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Second mode unstable disturbance measurement of hypersonic boundary layer on cone by wavelet transform

2011

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“…[1] The higher surface heating and skin friction cause extra burdens for the thermal protection system and thus result in a reduction of payload, [2] as well as significant impacts on the performance control, fuel consumption, and structural design of hypersonic vehicles. [3] The accurate prediction of the laminarturbulence transition position [4] is the key in designing hypersonic vehicles. The laminar-turbulence transition process is characterized by the development of instability modes in a boundary layer.…”

mentioning

confidence: 99%

Dynamics Evolution Investigation of Mack Mode Instability in a Hypersonic Boundary Layer by Bicoherence Spectrum Analysis

Han¹,

Jiang²

2012

Chinese Phys. Lett.

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The instability of a hypersonic boundary layer on a cone is investigated by bicoherence spectrum analysis. The experiment is conducted at Mach number 6 in a hypersonic wind tunnel. The time series signals of instantaneous fluctuating surface-thermal-flux are measured by Pt-thin-film thermocouple temperature sensors mounted at 28 stations on the cone surface along streamwise direction to investigate the development of the unstable disturbances. The bicoherence spectrum analysis based on wavelet transform is employed to investigate the nonlinear interactions of the instability of Mack modes in hypersonic laminar boundary layer transition. The results show that wavelet bicoherence is a powerful tool in studying the unstable mode nonlinear interaction of hypersonic laminar-turbulent transition. The first mode instability gives rise to frequency shifts to higher unstable modes at the early stage of hypersonic laminar-turbulent transition. The modulations subsequently lead to the second mode instability occurrence. The second mode instability governs the last stage of instability and final breakdown to turbulence with multi-scale disturbances growth.

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“…Unlike the case of subsonic flow, the mechanisms underlying the laminar-turbulence transition in hypersonic flow still are poorly understood. [3,4] The uncertainty in the prediction of the transition location results in overly conservative designs that are not optimally efficient. At hypersonic velocities, for Mach numbers greater than 4-4.5, a new acoustic type of instability (the socalled second mode instability) [5,6] arises in addition to the vortex instability mode (the first mode instability).…”

mentioning

confidence: 99%

Wavelet Cross-Spectrum Analysis of Multi-Scale Disturbance Instability and Transition on Sharp Cone Hypersonic Boundary Layer

Han

Jiang

2008

Chinese Phys. Lett.

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Experimental measurement of hypersonic boundary layer stability and transition on a sharp cone with a half angle of 5 • is carried out at free-coming stream Mach number 6 in a hypersonic wind tunnel. Mean and fluctuation surface-thermal-flux characteristics of the hypersonic boundary layer flow are measured by Pt-thin-film thermocouple temperature sensors installed at 28 stations on the cone surface along longitudinal direction. At hypersonic speeds, the dominant flow instabilities demonstrate that the growth rate of the second mode tends to exceed that of the low-frequency mode. Wavelet-based cross-spectrum technique is introduced to obtain the multi-scale cross-spectral characteristics of the fluctuating signals in the frequency range of the second mode. Nonlinear interactions both of the second mode disturbance and the first mode disturbance are demonstrated to be dominant instabilities in the initial stage of laminar-turbulence transition for hypersonic shear flow.

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VITA measurements of transition in transitional hypersonic boundary layer flows

Cited by 4 publications

References 19 publications

Second mode unstable disturbance measurement of hypersonic boundary layer on cone by wavelet transform

Second mode unstable disturbance measurement of hypersonic boundary layer on cone by wavelet transform

Dynamics Evolution Investigation of Mack Mode Instability in a Hypersonic Boundary Layer by Bicoherence Spectrum Analysis

Wavelet Cross-Spectrum Analysis of Multi-Scale Disturbance Instability and Transition on Sharp Cone Hypersonic Boundary Layer

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