By impacting a concave dual-layer liquid (with the oil and the dyed water) surface in a test tube, a compound jet with a water core and an oil shell is generated. The velocities of the jet’s head (V)_j and the oil-water interface (V′_j) are experimentally determined against the initial thickness and the viscosity of the upper layer liquid. The results show that the oil-water interface can be roughly regarded as a pure material surface, whose velocity can be determined from the jet velocity and the initial location (or the film thickness). Furthermore, the effective density, viscosity and surface tension of the compound jet are used to evaluate the jetting velocity. The previous scaling relation for a single liquid jet can be used to give a good prediction with the effective quantities. The results of this paper can be used for the compound jet/droplet preparation.

通过在试管中撞击凹入的双层液体表面（带有油和染色的水），可产生具有水芯和油壳的复合射流。射流头（V）_j和油水界面的速度（_V'j）是根据上层液体的初始厚度和粘度通过实验确定的。结果表明，油水界面可以粗略地看作是纯净的材料表面，其速度可以根据射流速度和初始位置（或膜厚）确定。此外，使用复合射流的有效密度，粘度和表面张力来评估射流速度。单个液体射流的先前比例关系可用于使用有效量给出良好的预测。本文的结果可用于复合射流/液滴的制备。