# I cant create the External Flow Volume Mesh **URL:** \ **Category:** Project Support\ **Created:** [September 16, 2021, 4:11pm UTC](https://www.simscale.com/forum/t/i-cant-create-the-external-flow-volume-mesh/93932 "2021-09-16T16:11:13Z")\ **Posts on this page:** 1\ **Showing post:** 4
**Author:** ![RicardoParis](https://www.simscale.com/forum/user_avatar/www.simscale.com/ricardoparis/32/30222_2.png) [@RicardoParis](https://www.simscale.com/forum/u/RicardoParis)\ **Post date:** [September 16, 2021, 8:37pm UTC](https://www.simscale.com/forum/t/i-cant-create-the-external-flow-volume-mesh/93932/4 "2021-09-16T20:37:30Z")
This one works better, thanks. In short, a sheet body is a non-watertight geometry. It consists of faces only, and it’s completely hollow inside (i.e. it has no volume). Repairing this kind of geometry can be very tricky (see [this article](https://www.simscale.com/knowledge-base/how-to-find-faults-in-the-cad-model-2/)). It consists of finding where the holes in the topology are, and closing them. The idea is not to have any free boundaries/naked edges that cause the geometry to be non-watertight. Typically the best tool to fix the issue is the same one that constructed the geometry. On a side note, I would really recommend using a smoother geometry for the simulation, the topology is quite detailed with hundreds of small faces: ![image](https://www.simscale.com/forum/uploads/default/original/3X/b/3/b3f743d3d1e7fc91410843131d9b09df368532eb.jpeg) This doesn’t mean that the CAD model is wrong, just that it’s not very good for a CFD simulation. I don’t think it’s possible to run a model this complex with a community account. The other model that you linked (which is working) is definitely cleaner. Cheers --- _[View the full topic](https://www.simscale.com/forum/t/i-cant-create-the-external-flow-volume-mesh/93932)._