1. 1 Liquid-crystal thermography method for the study of stages of instability developing in the cross- flow on the leading edge of the oblique wing Tolkachev S.N. Gorev V.N. Kozlov V.V.

2. 2 Boundary layer on the oblique wing

3. 3 LC thermography method c)c) a) Mechanismb) Location on the wing c) Typical visualisation picture for undisturbed flow features: - Multiuse - Qualitative ohmic heater with uniform distribution of heat power needed - Qualitative digital camera needed to receive the right color capture - Lag attainment of stationary regime is about 20-30 minutes (wing design heating) - Stationary disturbances visualization - Heat influence on the flow (destabilize) a)a)b)b)

4. 4 Experimental setup Slip angle: 45° Angle of attack: 0.2° Free-stream flow velocity: 2.8 – 24 m/s

5. 5 Roughness kit In experiments we used kit of three spherical roughness with leg, which allows to locate on the wing model.

6. 6 Roughness size U ∞ = 7.6 m/sU ∞ = 3.4 m/sU ∞ = 9.4 m/s d = 1 mm d = 2 mm d = 3 mm

7. 7 Experimental setup Slip angle: 45° Angle of attack: -7.2° Free-stream flow velocity: 8.1 – 10.9 m/s

8. 8 Roughness element Cylindrical roughness with glue substrate, which allows to locate on the random place of the wing model

9. 9 Roughness location

10. 10 Liquid crystal thermography

11. 11 Turbulator U ∞ = 24 m/s No blowingBlowing Real colors Hue channel

12. 12 Turbulator U ∞ = 13 m/s

13. 13 Conclusion Investigations in speed interval between 2.8 m/s and 24 m/s showed, that the turbulence doesn’t develop along the leading edge. Moreover the streaky structures appeared on the separate cornes of turbulator on low speed of the flow Stationary disturbances appear and develop behind the roughness The increase of the roughness size leads to the increase of the stationary disturbance magnitude There is the area of maximum receptivity to the roughness location on the leading edge of the oblique wing