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Multimedia files – 9/13
Streak instability in adverse pressure gradient boundary layer
Contents:
1. Test model2. Basic flow3. 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 boundarylayer 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 – UB
and rms velocity u' (shading); negative contours are shown by blue lines; depicted red arc hasdiameter of 2 mm; contour step is 0.2U0.5 for U - UB, and 0.02Ue for u' (a). Instantaneous spatialdistribution of utot, iso - levels are +3.5% of Ue(grey) and –3.5% of Ue(blue) (b)
(see page of notes)
(x-x1 )/1= 173
(x-x1 )/1= 119
(x-x1 )/1= 79
3. Varicose instability of the streak, ZPG (I)
(a) (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 utot = uave – UB
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) (b)
(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 uave = U + u'
3. Varicose instability of the streak, ZPG (IV)
Click to play
![Page 8: Multimedia files – 9/13 Streak instability in adverse pressure gradient boundary layer Contents: 1. Test model 2. Basic flow 3. Varicose instability of](https://reader035.vdocuments.mx/reader035/viewer/2022062618/55143668550346dd488b6244/html5/thumbnails/8.jpg)
(a) (b)
4. Varicose instability of the streak, APG (I)
Varicose instability of the streaky structure, APG. Contours of mean disturbance velocity U – UB
and rms velocity u' (shading); negative contours are shown by blue lines; depicted red arc hasdiameter of 2 mm; contour step is 0.2U0.5 for U - UB, and 0.02Ue for u' (a). Instantaneous spatialdistribution of utot, iso - levels are +2.0% of Ue(grey) and –2.0% of Ue(blue) (b)
(see page of notes)
![Page 9: Multimedia files – 9/13 Streak instability in adverse pressure gradient boundary layer Contents: 1. Test model 2. Basic flow 3. Varicose instability of](https://reader035.vdocuments.mx/reader035/viewer/2022062618/55143668550346dd488b6244/html5/thumbnails/9.jpg)
A video clip by Chernoray V.G., Kozlov V.V., Löfdahl L., Litvinenko Yu.A. (2004)illustrating the behavior of utot = uave – UB
4. Varicose instability of the streak, APG (II)
Click to play
![Page 10: Multimedia files – 9/13 Streak instability in adverse pressure gradient boundary layer Contents: 1. Test model 2. Basic flow 3. Varicose instability of](https://reader035.vdocuments.mx/reader035/viewer/2022062618/55143668550346dd488b6244/html5/thumbnails/10.jpg)
(a) (b)
(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)
![Page 11: Multimedia files – 9/13 Streak instability in adverse pressure gradient boundary layer Contents: 1. Test model 2. Basic flow 3. Varicose instability of](https://reader035.vdocuments.mx/reader035/viewer/2022062618/55143668550346dd488b6244/html5/thumbnails/11.jpg)
A video clip by Chernoray V.G., Kozlov V.V., Löfdahl L., Litvinenko Yu.A. (2004)illustrating the behavior of uave = U + u'
4. Varicose instability of the streak, APG (IV)
(see page of notes)
Click to play
![Page 12: Multimedia files – 9/13 Streak instability in adverse pressure gradient boundary layer Contents: 1. Test model 2. Basic flow 3. Varicose instability of](https://reader035.vdocuments.mx/reader035/viewer/2022062618/55143668550346dd488b6244/html5/thumbnails/12.jpg)
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.