You don't need to select the moving mesh. Just select the boundary of the cylinder as 'wall' and specify the wall as moving, then select 'rotating', then put the rotating wall in ' rad/sec'.

approximate the domain field as two-diminsonal and specify the axis of rotation as the first step

i tried modelling in 3D using sliding mesh model. But i get some negative cell zone error. But 2D is working fine

You don't need to select the moving mesh. Just select the boundary of the cylinder as 'wall' and specify the wall as moving, then select 'rotating', then put the rotating wall in ' rad/sec'.

If you interest about the heat transfer from / to the rotating cylinder, please notice:

https://www.researchgate.net/publication/311278595_Investigation_of_Heat_Transfer_and_Fluid_Mechanics_across_a_Heated_Rotating_Circular_Cylinder_in_Crossflow

https://www.researchgate.net/publication/309335286_Investigation_of_Heat_Transfer_and_Fluid_Mechanics_across_a_Heated_Rotating_Circular_Cylinder_in_Crossflow?_iepl%5BviewId%5D=OzDEywmAYRaJQ3TrFqqHjoZ9&_iepl%5BprofilePublicationItemVariant%5D=default&_iepl%5Bcontexts%5D%5B0%5D=prfpi&_iepl%5BtargetEntityId%5D=PB%3A309335286&_iepl%5BinteractionType%5D=publicationTitle

https://www.researchgate.net/publication/311063828_Experimental_and_Numerical_Investigation_of_Heat_Transfer_and_Fluid_Mechanics_across_a_Rotating_Circular_Cylinder_Dissipating_Uniform_Heat_Flux_by_Crossflow?_iepl%5BviewId%5D=OzDEywmAYRaJQ3TrFqqHjoZ9&_iepl%5BprofilePublicationItemVariant%5D=default&_iepl%5Bcontexts%5D%5B0%5D=prfpi&_iepl%5BtargetEntityId%5D=PB%3A311063828&_iepl%5BinteractionType%5D=publicationTitle

https://www.researchgate.net/publication/281639011_Experimental_and_Numerical_Investigation_of_Heat_Transfer_and_Fluid_Mechanics_across_a_Rotating_Circular_Cylinder_Dissipating_Uniform_Heat_Flux_by_Crossflow

If you interest about the cylinder with/ without heat transfer and focus on the hydrostatic characters please notice:

https://www.researchgate.net/publication/309152614_Experimental_and_theoretical_investigation_of_the_effect_of_rotating_circular_cylinder_speed_on_the_lift_and_drag_forces

Good luck

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I am trying to model inviscid flow over a rotating cylinder in fluent. But when I select the model- inviscid, the option to input rotation on cylinder turns off. So how can I model potential flow over a rotating cylinder in ansys fluent?

In case of inviscid flow, due to slip at wall rotation of cylinder may have no any effect on the fluid flowing over the cylinder.