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Multimedia files – 13/13 Origination and evolution of turbulent spots

Multimedia files – 13/13 Origination and evolution of turbulent spots. Contents : 1. Incipient spot 2. Turbulent spot 3. Turbulent spot structure 4. Turbulent spot evolution 5. Interaction of turbulent spots 6. Turbulent spots at low and high free stream turbulence

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Multimedia files – 13/13 Origination and evolution of turbulent spots

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  1. Multimedia files – 13/13 Origination and evolution of turbulent spots Contents: 1. Incipient spot 2. Turbulent spot 3. Turbulent spot structure 4. Turbulent spot evolution 5. Interaction of turbulent spots 6. Turbulent spots at low and high free stream turbulence 7. Transformation of L - structures into turbulent spots 8. Related publications

  2. 1. Incipient spot Smoke visualization of an incipient spot during natural transition on a flatplate at high free-stream turbulence, Tu = 1.5% (Alfredsson et al. 1996) (see page of notes)

  3. 2. Turbulentspot (I) Turbulent spot (Alfredsson et al. 1996) (see page of notes)

  4. 2. Turbulentspot (II) Set-up of the turbulent spots visualization in a boundary layer (Alfredsson et al. 1996 ) (see page of notes)

  5. 2. Turbulentspot (III) Click to play Uo Undisturbed flat-plate boundary layer at Tu = 0.01% (video clip by Alfredsson P.H., Bakchinov A.A., Kozlov V.V, and Matsubara M., 1996)

  6. 2. Turbulentspot (IV) Click to play Uo Turbulent spots on flat plate at Tu = 0.01%, U0 = 9.0 m/s (video clip by Alfredsson P.H., Bakchinov A.A., Kozlov V.V, and Matsubara M., 1996)

  7. 3. Turbulentspot structure Ensemble-averaged oscillogramsacross the turbulent spot in theplane of its symmetry in a flat plateboundary layer (Grek et al. 1987).Characteristic regions and fronts ofthe spot are marked by numbers, asin (Wygnanski et al. 1982), and lettersas in (Cantwell et al. 1978):1(A), spot leading front near wall;2(B), leading front forward-most region;3(C), maximum spot height;4(F), spot trailing edge; D, regionof velocity relaxationto undisturbedstate (see page of notes)

  8. 4. Turbulent spot evolution Propagation velocity of the turbulentspotfronts in a flat-plate flow: leadingfront, LF(1), trailingfront,TF(4). Experimental data by Greketal. (1987) at Tu≤0.04% (1), Greketal. (1987) at Tu=1% (2), and Wygnanskietal. (1982) (3); x0 = 300 mm, U0 = 10 m/s, for other notations see legend to the previous figure (see page of notes)

  9. 5. Interaction of turbulent spots (I) Development and merging of two turbulent spots spaced in the spanwise direction (Grek et al. 1987) (see page of notes)

  10. 5. Interaction of turbulent spots (II) Development and interaction of two turbulent spots that are following each other (Grek et al. 1987) (see page of notes)

  11. 6. Turbulent spots at low and high free stream turbulence (I) Smoke visualization of the turbulent spots in a flat plate boundary layerat low (top) and high (bottom) free-stream turbulence (Alfredsson et al. 1996) (see page of notes)

  12. 6. Turbulent spots at low and high free stream turbulence (II) Development characteristics of the ensemble-averaged turbulent spotat low and high free-stream turbulence:the turbulent spot structure along itscentreline (a); oscillograms demonstrating propagation characteristics of the turbulentspot fronts at U0 = 10 m/s, x0 = 300 mm,Tu≤0.04% (green lines), Tu = 1% (red lines) (Grek et al. 1987, 1988) (b) (see page of notes)

  13. 7. Transformation of L - structures into turbulent spots (I) Experimental setup (see page of notes)

  14. 7. Transformation of L - structures into turbulent spots (II) Amplitude contours of the ensemble-averaged L-structure at its downstream propagation in x-z plane

  15. 7. Transformation of L - structures into turbulent spots (III) Click to play U0 Hot-wire ‘visualization’ of the L- structure transformation into the turbulent spot, x-z plane (video clip by Chernoray V.G., Kozlov V.V., Löfdahl L., Litvinenko Yu.A., Grek G.R., Chun H.H., 2005)

  16. 7. Transformation of L - structures into turbulent spots (IV) Click to play U0 Hot-wire ‘visualization’ of the L- structure transformation into the turbulent spot, 3D space (video clip by Chernoray V.G., Kozlov V.V., Löfdahl L., Litvinenko Yu.A., Grek G.R., Chun H.H., 2005)

  17. 8. Related publications (I) Alfredsson P.H., Bakchinov A.A., Kozlov V.V., Matsubara M. (1996)Laminar–turbulent transition at a high level of a free stream turbulence.In P.W. Duck and P.Hall (Eds.),Nonlinear Instability and Transition inThree- Dimensional Boundary Layers (423–436). Dordrecht: Kluwer. Amini J., Lespinard G. (1982) Experimental study of an "incipient spot" in a transitional boundary layer. Phys. Fluids, 25, 1743-1750. Barrow J., Barnes F.H., Ross M.A.S. (1984) The structure of a turbulent spot in Blasius flow. J. Fluid Mech., 149, 319-337. Breuer K.S., Landahl M.T. (1990) The evolution of a localized disturbance in a laminar boundary layer. Part 2. Strong disturbances J. Fluid Mech., 220, 595-621. Cantwell D., Coles D., Dimotakis P. (1978) Structure and entrainment in the plane of symmetry of a turbulent spot. J. Fluid Mech., 87, 641-671. Chernoray V.G., Grek G.R., Kozlov V.V., Litvinenko Yu.A. (2010) Spatial hot-wire visualization of the L-structure transformation into the turbulent spot on the smooth flat plate surface and riblet effect on this process. J. Visualization, 13(2), 151-158. Elder J.W. (1960) An experimental investigation on turbulent spot and breakdown to turbulence. J. Fluid Mech., 9., 235-246. Emmons H.W. (1951) The laminar-turbulent transition in a boundary layer. Part 1. J. Aeronaut. Sci.,18(7), 490-498. Grek G.R., Kozlov V.V., Ramazanov M.P. (1987) Laminar–turbulent transition at highfree stream turbulence. Preprint ITAM 8–87. Grek G.R.,Kozlov V.V.,Ramazanov M.P. (1990)Investigation of boundary-layer stability in a pressure gradient flow at high free-stream turbulence. Fluid Dynamics, 2, 52-58. Litvinenko Yu.A., Chernoray V.G., Kozlov V.V., Loefdahl L., Grek G.R., Chun H.H. (2006) The Influence of Riblets on the Development of a L-Structure and Its Transformation into a Turbulent Spot. Doklady Physics, 51(3), 144–147.

  18. 8. Related publications (II) Litvinenko Yu.A., Chernoray V.G., Kozlov V.V., Loefdahl L., Grek G.R. (2007) Control of L-structure transformation into the turbulent spot by means of riblets. In Proc. Intern. Conf. on the Methods of Aerophys. Research (pt.1,152-156). Novosibirsk. Matsubara M., Kozlov V., Alfredsson P.H., Bakchinov A.A., Westin,K.J.A. (1996) On flat plate boundary layer perturbations at high freestream turbulence level.In Proc. Eighth Internat. Conf. on Methodsof Aerophysical Research (pt.1, 174–179). Novosibirsk. Narasimha R., Subramanian C., Badri Narayanan M.A. (1982) Turbulent spot growth in favourable pressure gradients. Rep. 82 FM 12, Bangalore, India. Schubauer G.B., Klebanoff P.S. (1956) Contributions on the mechanics of boundary layer transition. NACA Rep. - No. 1289. Vasudevan K.P., Dey J., Prabhu A. (2001) Spots propagation characteristics in laterally strained boundary layers. Exp Fluids 30(5), 488–491. Wygnanski I., Sokolov M., Friedman D. (1976) On a turbulent spot in a laminar boun-dary layer. J. Fluid Mech., 78, 785-819. Wygnanski I., Haritonidis J.H., Kaplan R.E. (1979) On a Tollmien-Schlichting wave packet produced by a turbulent spot. J. Fluid Mech., 92, 505-528. Wygnanski I., Haritonidis J.H., Zilberman H. (1982) On the spreading of a turbulent spot in the absence of a pressure gradient. J. Fluid Mech., 123, 69-90.

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