For a given column diameter, fluid inlet diameter and number of
fluid inlets, when a given bed of solids are in complete swirled state,
the fluid jet will have only the tangential component of velocity
when it just emerges from the fluid inlet; as the fluid moves up taking
a spiral path along the column wall, entire bed of solids are kept
in a swirled state, but the tangential component of jet velocity continues
to decrease along its flow path. At a certain vertical height in
the column the tangential component of velocity may die out completely
and all the fluid moves up vertically. However, the average
value of tangential component may be sufficient to keep the entire
bed in a completely swirled state.