EXPERIMENTS OF CROSS-FLOW INSTABILITY IN A SWEPT-WING BOUNDARY LAYER

摘要

Stationary cross-flow instabilities and transitionpattern in the boundary layer of a 45-degreeswept wing with and without 3D artificialleading edge roughness were investigated bysublimation method in two wind tunnels ofNorthwestern Polytechnical University. For theexperiments in Low Turbulence Wind Tunnel,straight transition lines behind the minimumpressure point which are dominated by T-Sinstabilities appeared on the model withoutartificial roughness in the Reynolds numberrange of 5.50×10~5～1.65×10~6. The traces of themost amplified stationary cross-flow waveswere detected when Re≥1.38×10~6, and thespacing of stripes is consistent with the resultsof linear stability theory. The extreme sensitivityof the stationary disturbance to leading edgeroughness is verified at Re=1.65×10~6. Withdifferent spacing leading edge roughnessapplied, the most amplified waves weresuppressed by the 2.5mm spacing roughness,and harmonics with half of the inputwavelengths appeared when 6.0-8.0mm spacingroughness were printed. In NF-3 wind tunnel,the experiments found that as turbulence levelincrease, the amplification of stationary crossflowwaves are suppressed. Jagged transitionline dominated by stationary cross-flow wavesappeared in the upstream region of theminimum pressure point at Re=2.20×10~6, andthe transition was delayed successfully when1.7mm leading edge roughness was printed.