A laser technique was developed for the purpose of investigating the movement of particles in a two-dimensional gas-fluidized bed. With the aid of this technique three typical modes of these particles movements influenced by the bubble were observed. A wake renewal length was measured. It was discovered that

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the ratio of wake volume to bubble volume

should be considered not as a constant throughout the bed but as a function of the bubble volume. Under the same superficial gas velocity through the bed

the intensity of particle circulation was different at different heights and heigher levels more intensified circulations were

observed.