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

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

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

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 = Varicose instability of the streak, ZPG (I) (a)(a) (b)(b)

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

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)

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

(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)

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

(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)

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

5. Related publications Andersson, P., Brandt, L., Bottaro, A., Henningson D.S. (2001) On the breakdown of boundary layer streaks. J. Fluid Mech., 428, Asai M., Minagawa M., Nishioka M. (2002) The stability and breakdown of near-wall low-speed streak. J. Fluid Mech., 455, 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), 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), 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, 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, (1) (3). Skote M., Haritonidis J.H., Henningson D.S. (2002) Varicose instabilities in turbulent boundary layers. Phys. Fluids, 4(7),