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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.

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Boundary layer on the oblique wing

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LC thermography method

c)a) Mechanism b) 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) b)

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Experimental setup

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

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Roughness kit

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

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Roughness size

U∞ = 7.6 m/sU∞ = 3.4 m/s U∞ = 9.4 m/s

d = 1 mm

d = 2 mm

d = 3 mm

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Experimental setup

Slip angle: 45° Angle of attack: -7.2° Free-stream flow velocity: 8.1 –

10.9 m/s

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Roughness element

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

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Roughness location

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Liquid crystal thermography

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Turbulator

U∞ = 24 m/s

No blowing Blowing

Real colors

Hue channel

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Turbulator

U∞ = 13 m/s

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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