| 1. |
|
|
| 2. |
- Chernoray, Valery, 1975, et al.
(författare)
-
Effect of riblets on nonlinear disturbances in the boundary layer
- 2006
-
Ingår i: Thermophysics and Aeromechanics. ; 13:1, s. 67-74
-
Tidskriftsartikel (refereegranskat)abstract
- Results of experimental investigations of the nonlinear stage of sinusoidal and varicose instability of a streaky structure, which leads to multiplication of streaky structures and origination of coherent structures (such as Λ-structures), are presented. Riblets suppress the intensity of streaky structures, stabilize the flow against the development of the secondary high-frequency instability of streaky structures, and, for this reason, delay spatial turbulization of the flow. The results of these investigations can be useful for understanding the flow structure in such situations and for possible controlling of the coherent structures aimed at flow stabilization
|
|
| 3. |
- Chernoray, Valery, 1975, et al.
(författare)
-
Features of laminar-turbulent transition of adverse pressure gradient flows at low and high Reynolds numbers
- 2006
-
Ingår i: Proc. of the 6th Euromech Fluid Mechanics Conference, 2006, Stockholm, Sweden. ; , s. 82-
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Recent experimental studies of laminar-turbulent transition are presented withfocus on adverse pressure gradient flows. New developments in secondary instabilityof streaks and separation control are reported. In the first part of the presentation thestudies of laminar-turbulent transition in non-swept and swept wing boundary layersare discussed, and in the second part the investigations of separated flows on wingswith ordinary (plain) and modified (wavy-shaped) surfaces are considered. The role ofthree-dimensional velocity perturbations such as streamwise vortices and streaks in thelaminar-turbulence transition process is demonstrated, and the importance ofsecondary instability mechanisms is outlined. For a straight wing, the experimentalstudies of the nonlinear varicose secondary instability are compared at zero andadverse streamwise pressure gradients. Results obtained testify to the strong influenceof the pressure gradient upon the breakdown of streaks with developed instability [1].For the swept wings, the stationary vortex packets are most likely to be generatedunder natural flight conditions and transition to turbulence is known to be thequickest within these disturbances. Two modes of the secondary instability are foundto develop and the preferred mode is dependent on the properties of the primarystationary disturbance. The instability modes studied are the 'y' and 'z' high-frequencysecondary instability modes, which are investigated separately and also theirinteraction under fully controlled experimental conditions [2]. Furthermore, theinfluence of wing surface modifications on the wing performance and drag is studied.The results testify that for the low-Reynolds-number flow conditions the critical angleof attack of a wing with a wavy-shaped surface can be up to 1.5 times or more thanthat of a similar plane-surface-wing, and for the attack angles in the range between 5and 20 degrees the wing with a modified surface reveal higher aerodynamic qualityowing to decreased size of the separated zones [3].1 Litvinenko et al., Phys. Fluids 17, 118106 (2005).2 Chernoray et al., J. Fluid Mech. 534, 295 (2005).3 Kozlov et al., Proc. EUCASS Conf. Moscow, Russia, Paper 2.11.07 (2005).
|
|
| 4. |
- Chernoray, Valery, 1975, et al.
(författare)
-
Generation of the localized disturbances by the vibrating surface
- 2000
-
Ingår i: Thermophysics and Aeromechanics. ; 7:3, s. 329-339
-
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.
|
|
| 5. |
- Chernoray, Valery, 1975, et al.
(författare)
-
Instability of a swept-wing boundary layer modulated by stationary flow perturbations
- 2013
-
Ingår i: Visualization of Mechanical Processes: An International Online Journal. - 2152-209X. ; 3:1
-
Tidskriftsartikel (refereegranskat)abstract
- A collection of illustrations of swept-wing boundary layer secondary instability at low subsonic flow velocities is presented in this paper. The experimental results, obtained by hot-wire "visualization," provide detailed insight into the spatio-temporal structure and evolution of oscillations in the three-dimensional laminar boundary layer disturbed by longitudinal vortices and streaky structures.
|
|
| 6. |
- Chernoray, Valery, 1975, et al.
(författare)
-
Riblet-assisted control of transformation of the Λ-structure into a turbulent spot
- 2005
-
Ingår i: Thermophysics and Aeromechanics. - 0869-8643. ; 12:4, s. 539-548
-
Tidskriftsartikel (refereegranskat)abstract
- Experimental results are presented on transformation of a solitary Λ-structure into a turbulent spot and control of this process by means of riblets on the wetted surface in the boundary layer on a flat plate. It is shown that riblets exert a stabilizing effect on transformation of the Λ-structure into a turbulent spot. The Λ-structure on a smooth surface is shown to stretch in the streamwise direction and transform into a hairpin vortex, which becomes a turbulent spot further downstream. The intensity of the Λ-structure on riblets first increases and then decays further downstream, reaching less than half its value on a smooth surface. Finally, the Λ-structure decays on riblets without forming a turbulent spot.
|
|
| 7. |
- Chernoray, Valery, 1975, et al.
(författare)
-
Spatial hot-wire visualization of the Lambda-structure transformation into the turbulent spot on the smooth flat plate surface and riblet effect on this process
- 2010
-
Ingår i: Journal of Visualization. - : Springer Science and Business Media LLC. - 1343-8875 .- 1386-6478 .- 1875-8975. ; 13:2, s. 151-158
-
Tidskriftsartikel (refereegranskat)abstract
- Evolution of the Lambda-vortex and its transformation into the turbulent spot in a flat plate boundary layer are investigated experimentally. Extensive measurements visualizing the Lambda-structure transformation into the turbulent spot on the smooth and ribbed surfaces of the flat plate are presented. The flow behavior in the course of spatial evolution of the Lambda-structure and turbulent spot is discussed. Specific features of the downstream evolution of Lambda-structure and turbulent spot on the smooth and ribbed surfaces are demonstrated, such as suppression by riblets of the Lambda-vortex transformation into the turbulent spot, appearance of the coherent structures of Lambda-vortex within ensemble-averaged turbulent spot, and oblique waves generation both by the Lambda-vortex and turbulent spot.
|
|
| 8. |
- Chernoray, Valery, 1975, et al.
(författare)
-
Study of the incipient spot breakdown controlled by riblets
- 2011
-
Ingår i: Progress in flight physics. Eds. Ph. Reijasse, D. Knight, M. Ivanov, and I. Lipatov EUCASS advances in aerospace sciences book ser. - 9782759806744 ; , s. 519-530
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
|
|
| 9. |
- Chernoray, Valery, 1975, et al.
(författare)
-
Study of the Incipient Spot Breakdown Controlled by Riblets
- 2012
-
Ingår i: EUCASS Book Series on Advances in Aerospace Sciences, Vol. 3, Progress in Flight Physics, [Edited by Ph. Reijasse, D. Knight, M. Ivanov, and I. Lipatov]. ; , s. 545-556
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
|
|
| 10. |
|
|
