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Multimedia files – 9/13 Streak instability in adverse pressure gradient boundary layer Contents: 1. Test model 2. Basic flow 3. Varicose instability of the streak, ZPG 4. Varicose instability of the streak, APG 5. Related publications

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1. Test model (see page of notes) Sketch of the experimental model

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Characteristics of the undisturbed boundary layer at zero and adverse pressure gradients: velocity variation along the external boundary layer edge (a), variation of the boundary layer momentum thickness (b), and the velocity profiles (c); hot-wire data (symbols), theoretical approximations (lines) 2. Basic flow

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Varicose instability of the streaky structure, ZPG. Contours of mean disturbance velocity U – U B and rms velocity u' (shading); negative contours are shown by blue lines; depicted red arc has diameter of 2 mm; contour step is 0.2 U 0.5 for U - U B, and 0.02U e for u' (a). Instantaneous spatial distribution of u tot, iso - levels are +3.5% of U e (grey) and –3.5% of U e (blue) (b) (see page of notes) (x-x 1 )/ 1 = 173 (x-x 1 )/ 1 = 119 (x-x 1 )/ 1 = 79 3. Varicose instability of the streak, ZPG (I) (a)(a) (b)(b)

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A video clip by Chernoray V.G., Kozlov V.V., Löfdahl L., Litvinenko Yu.A. (2004) illustrating the behavior of u tot = u ave – U B 3. Varicose instability of the streak, ZPG (II) Click to play

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Instantaneous distributions of fluctuation velocity as isosurface levels at ± 2 % (a), ± 1 % (b), and ± 0.5 % (c); negative levels are coloured dark grey (see page of notes) (a)(a)(b)(b) (c)(c) 3. Varicose instability of the streak, ZPG (III)

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A video clip by Chernoray V.G., Kozlov V.V., Löfdahl L., Litvinenko Yu.A. (2004) illustrating the behavior of u ave = U + u' 3. Varicose instability of the streak, ZPG (IV) Click to play

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(a)(a)(b)(b) 4. Varicose instability of the streak, APG (I) Varicose instability of the streaky structure, APG. Contours of mean disturbance velocity U – U B and rms velocity u' (shading); negative contours are shown by blue lines; depicted red arc has diameter of 2 mm; contour step is 0.2 U 0.5 for U - U B, and 0.02U e for u' (a). Instantaneous spatial distribution of u tot, iso - levels are +2.0% of U e (grey) and –2.0% of U e (blue) (b) (see page of notes)

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A video clip by Chernoray V.G., Kozlov V.V., Löfdahl L., Litvinenko Yu.A. (2004) illustrating the behavior of u tot = u ave – U B 4. Varicose instability of the streak, APG (II) Click to play

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(a)(a) (b)(b) (c)(c) 4. Varicose instability of the streak, APG (III) Instantaneous distributions of fluctuation velocity as isosurface levels at ± 7 % (a), ± 3 % (b), and ± 1 % (c); negative levels are coloured dark grey (see page of notes)

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A video clip by Chernoray V.G., Kozlov V.V., Löfdahl L., Litvinenko Yu.A. (2004) illustrating the behavior of u ave = U + u' 4. Varicose instability of the streak, APG (IV) (see page of notes) Click to play

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5. Related publications Andersson, P., Brandt, L., Bottaro, A., Henningson D.S. (2001) On the breakdown of boundary layer streaks. J. Fluid Mech., 428, 29-60. Asai M., Minagawa M., Nishioka M. (2002) The stability and breakdown of near-wall low-speed streak. J. Fluid Mech., 455, 289-314. Chernoray V.G., Kozlov V.V., Lee, I., Chun, H.H. (2007) Visualization of varicose instability of streaks in a boundary layer. J. Visualization, 10(2), 217-225. Chernoray V.G., Kozlov V.V., Löfdahl L., Chun, H.H. (2006) Visualization of sinusoidal and varicose instabilities of streaks in a boundary layer. J. Visualization, 9(4), 437-444. Kozlov V.V., Chernoray V.G., Litvinenko Yu.A., Löfdahl L. (2004) Breakdown of a streak via development of varicose secondary mode on the staight wing with pressure gradient. In Proc. of the Tenth European Turbulence Conference, 29 June-2 July, 2004, Norway,Trondheim, 77-80. Litvinenko Yu.A., Chernorai V.G., Kozlov V.V., Loefdahl L., Grek G.R., Chun H.H. (2005) Adverse pressure gradient effect on nonlinear varicose instability of a streaky structure in an unswept wing boundary layer. Phys. Fluids, 17, 118106(1)-118106(3). Skote M., Haritonidis J.H., Henningson D.S. (2002) Varicose instabilities in turbulent boundary layers. Phys. Fluids, 4(7), 2309-2323.

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