Aimed at the problem of self-sustaining oscillation at sheer layer induced by fluid separation in 3D cave-in cavity with different span in uniform flow field

a series of experiments were carried out.The influence of span change on self-sustaining oscillation characteristics of shear layer of 3D cave-in cavity was analyzed at 0° attack angle

Where Re=2.06×10-5～1.16×10-6.Circumferential fluid pressure at shear layer of 3D cave-in cavity is measured.Distribution rule of fluid pressure and self-sustaining oscillation characteristics of shear layer were analyzed.The results of experiment show that the increase of span of cave-in cavity will result in increase of steady state pressure coefficient at shear layer Cp

at the same time

it will bring the promotion of trailing edge of shear layer C′p.But the increase of span of cave-in cavity can induce the drop of self-sustaining oscillation frequency at shear layer.