越靠近自由表面，底部射流横向发展越窄，而向上的压力梯度，气泡上升速度，底部射流上升高度越大，反之则反；
The more the bubble close to the free surface, the narrower the bottom jet develops crosswise, and the larger the pressure gradient, the rising velocity and the height of the bottom jet is upwards.
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