In Poroelasticity, in order to decouple the hydromechanical coupled effects, a decomposition technique such as Biot's decomposition is used. The technique decomposes the displacement field into two parts i.i a time-independent part and a time-dependent part. the time-dependent dent part is said to be irrotational which its curl is zero. I need to know what are the properties of an irrotational displacement.

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