The FEM model of the mould for 7050 aluminum semi-continuous casting round billets was built up by CFD software Fluent

and flow filed of the aluminum alloy melts sonicated in the mould was analyzed

focusing on effects of acoustic streaming on the flow field. The results reveal that large-scale Echart acoustic streaming was formed in the liquid phase zone

driven by the radiation force which was formed as a result of the acoustic pressure gradient resulting from the viscous attenuation. As the amplitude and the scale of the Eckart acoustic streaming were much smaller than those of the flow field in the mould

effects of acoustic streaming on the flow filed can be neglected. The vortices from the flow field in nozzle transfer the effective nuclei and equiaxed grains formed in the cavitation area to the other area of the liquid pool and brings the other melt to the cavitation area in turn

forcing the others to be equiaxed grains and effective nuclei

finally

the structures of the ingot are all equiaxed grains. Effects of acoustic streaming on enlarging the refinement area can be negligible in the semi-continuous casting experiment.