Answer:
No
Step-by-step explanation:
We know that
Rationality in 3D flow is given as follows

If ω is equal to zero then flow will be irrotational and if ω is not equal to zero then flow will be rotational .
So if flow is ir-rotational it means that the component of ω in x-direction,in y-direction and in z-direction direction should be zero.
So it is not necessarily that 3D parallel flow will be irrotaional.