Hi @pkgannevaram, you need to understand that a flow region is simply a solid body that represents the region where the fluid (water in your case) will be. In the platform, your geometry was translated as 2 solids - if I delete this upper cylinder for instance, the meshing operation completes as happens in this copy of your project I’ve made: https://www.simscale.com/workbench/?pid=7375375296244811419
I’d advise you to take a look at some tutorials where flow regions are generated such as these 2:
- Conjugate Heat Transfer in U-Tube Heat Exchanger | SimScale
- Thermal Comfort In a Meeting Room | Tutorial | SimScale
to understand this important concept then remodel your CAD in a way that you’ll be able to generate it!
Cheers