| 1. |
- Bakchinov, A.A., et al.
(författare)
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Experimental study of the K-regime of breakdown in straight and swept wing boundary layers
- 2000
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Ingår i: Abstracts of 53rd Ann. Meeting of the Div. of Fluid Dyn. APS, Washington, DC.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Experiments on the stability of three-dimensional boundary layers on the straight and swept airfoils have been conducted. Detailed measurements of the streamwise velocity field in (Y, Z) planes, as well as the 3D frequency-wavenumber spectra have revealed linear and non-linear evolutions of the disturbances generated by an external acoustic field in the airfoil boundary layers. The Tollmien-Schlichting waves, excited by the sound, were dominant in both configurations, and the disturbance flow field was found to remain highly deterministic and periodic both in time and space until the latest stages of the transition. To control a spanwise variation of the disturbance flow field roughness elements were placed on the surface and equidistantly aligned along the airfoil leading edge. The K-type transition was identified with the aligned order of so-called Lambda-patterns at non-linear stage of the transition. The experiment was conducted in a closed-circuit wind-tunnel at the department of Thermo and Fluid Dynamics, Calmers. This work was supported by the Royal Swedish Academy of Sciences (KVA).
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| 5. |
- Chernoray, Valery, 1975, et al.
(författare)
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Experimental study of the K-regime of breakdown in straight and swept wing boundary layers
- 2001
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Ingår i: Physics of Fluids. ; 13:7, s. 2129-2132
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Tidskriftsartikel (refereegranskat)abstract
- In this Brief Communication, the nonlinear evolution of periodical disturbances generated by an external sound field in a swept wing boundary layer is presented. All experimental results are compared with corresponding data for a straight wing configuration. The Tollmien-Schlichting instability has been studied, and it was found that the disturbance flow field remained highly deterministic and periodic in both time and space until the latest stages of the transition. A frequency-wave number Fourier analysis shows that the disturbance spectra comprise only the fundamental wave and its higher harmonics. The K-type breakdown scenario was observed, and the nonsymmetry of flow patterns in the swept wing boundary layer was found to be due to the presence of the cross flow.
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| 6. |
- Chernoray, Valery, 1975, et al.
(författare)
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Generation of perturbations by a localized vibrator in the boundary layer of a nonswept wing
- 2001
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Ingår i: Journal of Applied Mechanics and Technical Physics. ; 42:5, s. 765-772
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Tidskriftsartikel (refereegranskat)abstract
- Origination and development of perturbations generated by a three-dimensional vibrating surface in the boundary layer on an airfoil with a zero sweep angle is experimentally studied. Surface vibrations were generated by a three-dimensional membrane. It is shown that high-amplitude vibrations of a three-dimensional surface lead to simultaneous formation of two types of perturbations in the boundary layer: quasi-stationary streamwise structures and wave packets accompanying them. The presence of regions with favourable and adverse pressure gradients does not exert a significant effect on evolution of streamwise structures but leads first to attenuation and then to amplification of wave packets.
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| 7. |
- Chernoray, Valery, 1975, et al.
(författare)
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Generation of the localized disturbances by the vibrating surface
- 2000
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Ingår i: Thermophysics and Aeromechanics. ; 7:3, s. 329-339
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Tidskriftsartikel (refereegranskat)abstract
- Appearance and development of disturbances generated by 3-D vibrating surface in Blasius boundary layer are studied experimentally. The experiments were conducted under the controlled conditions where the preservation of phase information made it possible to obtain profound and accurate data, qualitative as well as quantitative, on the object under study. Surface vibration was provided by the loudspeaker working in the blowing-suction regime. Detailed hot-wire measurements showed that in case when the surface produces oscillations of low frequency and small amplitude, the packet of disturbances with the characteristics of Tollmien - Schlichting (TS) waves is observed downstream. When the effective amplitude is increased two times "blowing" leads to the appearance of the new type of disturbances: "puff"-structures, which have other characteristics of development in the boundary layer than Tollmien - Schlichting waves.
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| 8. |
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| 9. |
- Chernoray, Valery, 1975, et al.
(författare)
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Secondary instability of stationary vortex packets in a swept wing boundary layer
- 2004
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Ingår i: In Proc. of XXI International Congress of Theoretical and Applied Mechanics, Warsaw, Poland.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The fact is that stationary vortex packets are most likely to be generated under natural flight conditions on the wing and these disturbances lead to breakdown the fastest. A detailed experimental study on the formation of crossflow vortex mode packets and their secondary instability in a swept wing boundary layer was carried out.
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