Abstract:

Turbulent bubbly mixing layer was experimentally investigated by PIV and analyzed by using the swirling strength method.The velocity ratio between high speed and low speed was 4∶1 and the Reynolds number based on the velocity difference of two streams and hydraulic channel diameter ranged from 4400 to 132000.Bubbles with a diameter from 0.5 mm to 2 mm were injected into the flow field at the end of the splitter and in the low speed side separately.By using the swirling strength method，the vortex structures excluded the effect of shear were shown clearly，and were concentrated in the coniform area of the central mixing flow field.With increasing Reynolds number，swirling strength increased and the coniform area became narrow.Swirling strength first increased and then decreased along the downstream direction at the same Reynolds number.When injected at the end of the splitter，most of the bubbles were distributed in the downstream [JP2]area of the mixing layer where swirling strength was larger.However，when the bubbles were injected in the low speed side，bubbles were mainly concentrated in the low speed side，but some of them could also be trapped by the vortex structures and move to the central part of the mixing layer.Compared with the single phase case，the results indicated that swirling strength was strengthened when the bubbles were injected at a low Reynolds number，while it was weakened at a high Reynolds number.