Some concepts you cannot afford to miss about Rotational and Irrotational flow


Basically there are two types of motion (i) Translation and (ii) Rotation. These two may exist independently or simultaneously.


  • Forced vortex is also known as flywheel vortex. = V/R =C (ESE OBJECTIVE)
  • Free vortex is also known as potential vortex. V.R=C
  • Compound vortex is combination of free and forced vortex also known as Rankine vortex. (ESE OBJECTIVE)
  • Spiral vortex (free vortex and a radial flow).
  • Rotation of a fluid, moving as a solid, about an axis is called forced vortex motion. Every particle of fluid will have same angular velocity.
  • Free vortex motion: Each particle moves in a circular path with speed varying inversely as the distance from the centre .V/R =C
  • Vortices can be classified based on vortex strength. A basic vortex also referred as bath tub vortex.
  • The mechanism of motion in the centrifugal compressor at inlet is forced vortex.
  • The mechanism at the inlet of KAPLAN TURBINE is free vortex. (based on question in ESE OBJECTIVE)

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