Once you performed the simulation, the length of the re-circulation region can be easily determined via the velocity vectors.

In the re-circulation zone the velocity vectors are in the opposite direction of the incident flow, however, at the end of this zone, the velocity vectors change their direction again towards the incident flow direction.

Hello Jagadeesan,

as far as I understood your problem, you might run an unsteady simulation. As you will have vortex shedding, your reattachment length is changing, consequently you have to activate time averaging before the simulation. You have to check the literature for the amount of flow through times, you need for averaging.

Once you have your simulation done, just make line plot and look at the velocity gradients or the skin friction, as already mentioned by Anbarsooz above. If you have a 3D geometry, your x_r might vary over the width.

I hope you got a better idea of how to solve your problem.

Kind regards.

Since you said 'vortex shedding doesn't start yet'

An unsteady simulation is not needed.

Thanks for the reply. Im not that familiar with flows at that low Re, therefore I assumed, that it might happen there as well.