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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

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 boundarylayer 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 – 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)

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

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)

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

(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)

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

(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)

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

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.