Hi @vyvo!
Before we talk about the boundary conditions may I ask why you decided for a RANS type simulation in this case? You have to keep in mind that statistics has been applied a priori to the equations and you will receive a time-averaged flow field corresponding to a long-time exposure. For a LES approach you might have a look at this project from my colleague Ali: Flow around a cylinder. Problem with k-epsilon and k-omega is that you have to make sure that the dissipation is not too high and that everything at the wall is well resolved (good thing we are using k-omega). However I would go for LES anyway and not use the whole length of the cylinder to observe the vortex shedding phenomenon/Kármán Vortex street (in case someone wants to know the precise name).
Before I forget it: Increase the side of your domain like 20xD from the inlet to the cylinder and maybe 40xD from the cylinder to the outlet and also in spanwise direction around 20-40xD. We can compare your results by using some data from the literature - can be done later on. Also do not use wall functions as the flow will separate from the surface of the cylinder thus wall functions will fail to predict the flow behavior anyway so make sure y^+ is around 1.
\underline{\text{Now talking about the parameters:}}
For omega you can use the formula from Darren in the post you mentioned or a slightly changed formula but still dimensionally consistent. For help take this calculator: http://ichrome.com/blogs/archives/342
And for the intensity you can not just go with the formula given by Darren in his post as this is for a pipe/duct. Last but not least let the solver output you the drag as well as the lift coefficient for reference later on. I am however not sure which intensity can be used in this case. I would definitely go with a highly turbulent behavior and use bigger than 5%.
Please add your two cents here @Get_Barried, @vgon_alves & @Anware if necessary and if you think I forgot something.
All the best and happy SimScaling,
Jousef