Hypersonic Laminar Flow Control Using a Porous Coating of Random Microstructure

Маслов, А. А.; Shiplyuk, A. N.; Sidorenko, A. A.; Polivanov, P. A.; Федоров, А. В.; Kozlov, V. F.; Malmuth, N.

doi:10.2514/6.2006-1112

Cited by 35 publications

(12 citation statements)

References 14 publications

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“…This trend is in agreement with literature results 7,23,38 and is probably due to the influence of the free-stream noise whose spectrum and intensity are functions of the free-stream unit Reynolds number.…”

supporting

confidence: 82%

Hypersonic Boundary Layer Transition on a 7 Degree Half-Angle Cone at Mach 10

Grossir

Regert

Pinna

et al. 2014

7th AIAA Theoretical Fluid Mechanics Conference

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Hypersonic boundary layer transition experiments are performed in the low-enthalpy Longshot wind tunnel with a free-stream Mach number ranging between 12 ≥ M∞ ≥ 9.5 and Reynolds number between 12 × 10 6 /m ≥ Reunit,∞ ≥ 3.3 × 10 6 /m. The model is an 800 mm long 7• half-angle cone with nosetip radii between 0.2 and 10 mm. Instrumentation includes flushmounted fast-response thermocouples and pressure sensors. Boundary layer transition onset location is determined from the wall heat flux distribution. Nose bluntness has a strong stabilizing effect. No transition reversal could be observed at RB = 10RN for a Reynolds number based on the nosetip radius of ReR N ,∞ = 123, 000. Increasing freestream unit Reynolds number results in larger Rex B ,e. Wavelet analysis of the boundary layer fluctuations shows that numerous wave packets are present during the transition process. Comparison with Linear Stability Theory results for second mode waves shows an excellent agreement for the most amplified frequencies. The N -factor of the wind-tunnel is 5 based on these computations and on the transition location measured experimentally. The convection velocity of the disturbances is closely approximated by the local boundary layer edge velocity for all conditions investigated. Schlieren flow visualization of the instabilities exhibits the typical rope shape of second mode disturbances for the sharpest nosetips. For nose bluntness larger than 4.75 mm, disturbances are mainly present at the edge of the boundary layer and within the inviscid shock layer. Their shape no longer presents the second mode typical structure although a frequency analysis of the disturbances is still compatible with second mode instabilities. Present results confirm the dominance of second mode waves in the transition process along a conical geometry for Mach numbers larger than 10.

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supporting

confidence: 82%

Hypersonic Boundary Layer Transition on a 7 Degree Half-Angle Cone at Mach 10

Grossir

Regert

Pinna

et al. 2014

7th AIAA Theoretical Fluid Mechanics Conference

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“…Fedorov et al , 2003aBountin et al 2004;Maslov et al 2006) have confirmed the UAC stabilization concept. More recently, direct numerical simulations (DNS) of both two-dimensional surfaces with regular spanwise slots (Brès, Colonius & Fedorov 2008b;Wartemann, Lüdeke & Sandham 2009;Hader & Fasel 2011), and three-dimensional surfaces with streamwise slots, and rectangular pores with various shapes De Tullio & Sandham 2010) have investigated aspects of linear and nonlinear instability and transition of UAC.…”

Section: Introductionmentioning

confidence: 58%

Second-mode attenuation and cancellation by porous coatings in a high-speed boundary layer

et al. 2013

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Numerical simulations of the linear and nonlinear two-dimensional Navier-Stokes equations, and linear stability theory are used to parametrically investigate hypersonic boundary layers over ultrasonic absorptive coatings. The porous coatings consist of a uniform array of rectangular pores (slots) with a range of porosities and pore aspect ratios. For the numerical simulations, temporally (rather than spatially) evolving boundary layers are considered and we provide evidence that this approximation is appropriate for slowly growing second-mode instabilities. We consider coatings operating in the typical regime where the pores are relatively deep and acoustic waves and second-mode instabilities are attenuated by viscous effects inside the pores, as well as regimes with phase cancellation or reinforcement associated with reflection of acoustic waves from the bottom of the pores. These conditions are defined as attenuative and cancellation/reinforcement regimes, respectively. The focus of the present study is on the cases which have not been systematically studied in the past, namely the reinforcement regime (which represents a worst-case scenario, i.e. minimal second-mode damping) and the cancellation regime (which corresponds to the configuration with the most potential improvement). For all but one of the cases considered, the linear simulations show good agreement with the results of linear instability theory that employs an approximate porous-wall boundary condition, and confirm that the porous coating stabilizing performance is directly related to their acoustic scattering performance. A particular case with relatively shallow pores and very high porosity showed the existence of a shorter-wavelength instability that was not initially predicted by theory. Our analysis shows that this new mode is associated with acoustic resonances in the pores and can be more unstable than the second mode. Modifications to the theoretical model are suggested to account for the new mode and to provide estimates of the porous coating parameters that avoid this detrimental instability. Finally, nonlinear simulations confirm the conclusions of the linear analysis; in particular, we did not observe any tripping of the boundary layer by small-scale disturbances associated with individual pores.

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“…For coldwall conditions relevant to experiment in shock tunnels [4,19], the wall temperature is T w 1, which gives at high Mach number 3-9 deg, close to 0 deg (i.e., normal incidence). For moderate cooling [8] and an adiabatic wall [5], the estimated angle of incidence decreases to 16 and 26 deg, respectively. In all cases, the angle of incidence relevant for UAC design is smaller than 26 deg.…”

Section: Effect Of Angle Of Incidencementioning

confidence: 99%

“…Wind-tunnel experiments and theoretical studies [3][4][5][6][7][8] have already demonstrated that an ultrasonically absorptive coating (UAC), which consists of a thin microporous layer, can suppress the second-mode instability and thereby delay transition of the predominately-two-dimensional boundary layer. Integration of this passive UAC device to thermal protection systems requires multidisciplinary efforts, including flow modeling, testing of materials and fabrication of prototypes.…”

mentioning

confidence: 99%

Acoustic Properties of Porous Coatings for Hypersonic Boundary-Layer Control

2010

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Numerical simulations are performed to investigate the interaction of acoustic waves with an array of equally spaced two-dimensional microcavities on an otherwise flat plate without external boundary-layer flow. This acoustic scattering problem is important in the design of ultrasonic absorptive coatings for hypersonic laminar flow control. The reflection coefficient, characterizing the ratio of the reflected wave amplitude to the incident wave amplitude, is computed as a function of the acoustic wave frequency and angle of incidence, for coatings of different porosities, at various acoustic Reynolds numbers relevant to hypersonic flight. Overall, the numerical results validate predictions from existing theoretical modeling. In general, the amplitude of the reflection coefficient has local minima at some specific frequencies. A simple model to predict these frequencies is presented. The simulations also highlight the presence of resonant acoustic modes caused by coupling of small-scale scattered waves near the coating surface. Finally, the cavity depth and the porosity are identified as the most important parameters for coating design. Guidelines for the choice of these parameters are suggested.

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Hypersonic Laminar Flow Control Using a Porous Coating of Random Microstructure

Cited by 35 publications

References 14 publications

Hypersonic Boundary Layer Transition on a 7 Degree Half-Angle Cone at Mach 10

Hypersonic Boundary Layer Transition on a 7 Degree Half-Angle Cone at Mach 10

Second-mode attenuation and cancellation by porous coatings in a high-speed boundary layer

Acoustic Properties of Porous Coatings for Hypersonic Boundary-Layer Control

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