Hi there! You will need to extract the flow region in order to simulate the air inside the model. To do so:
Open the CAD mode;
Select the Flow Volume at the top of the interface;
Select the seed and boundary faces accordingly, and create the flow volume;
Delete the pipe, so only the flow region remains;
Go back to the workbench by selecting the ‘Finish’ option.
Check this tutorial for example, that follows this workflow. The model is not deleted here, because it is a Conjugate Heat Transfer tutorial, where the heat transfer between solids and fluids is simulated.
Thank you for your reply. now Im facing this issue
" A setup with 2 regions is being used in a single-region analysis type. Please make sure that all regions except for one have an Advanced Concept assigned to them."
EDIT: my CAD file was made out of two bodies that was the issue. Thank you I have made mine first simulation