As i know the plates inside the clutch assembly are very close to each other,
but they are not in direct contact.
The difference in the rotational speed between the input and the output shafts,
creates shear effect in the special fluid, thus makes the fluid hot very quickly.
The plates are perforated in order to increase the shear effect.
The hot fluid is become almost solid, like a glue, making possible to transfer torque
between the plates (fluid coupling). The transfer characteristics of the clutch is mainly affected
by the perforation pattern of the plates (higher shear -> quicker engage) and the properties
of the special dilatant fluid (solidity vs temperature).
If the fluid reaches it's boiling temperature, that will permanently/irreversibly locks together