How do I generate Blocking for a Thick Pipe which is inside a another Pipe?How do I generate the Surfaces for a proper mesh?The flow is from the inner pipe to the outher pipe and then through between the walls further ahead....Anyone has a clue?

Use "O-Grid" splitting concept. It should help. If there is no fluid domain inside inner pipe then delete that block.

You need to again simply split this "O-Grid" blocking untill you get no. of blocks in radial direction equal to no. of domains/subdomains in radial direction.

Create different parts of surfaces in ICEM those you want to use as boundaries in CFX-Pre.

Also create bodies for all domain/subdomain in ICEM & include concerned blocks in to it.

I can only advise this much until you let us know more about your problem.

Good luck.

Also do not forget to associate edges & vertices of blocks to curves & points of geometry respectively.

Thanks.......I am taking a 15 degree piece due to symmetry.What i do is make a surface for each surface present...the inner cylinder does not start exactly at the outer cylinder circular surface but 5 mm inside....i also made a surface there...the flow is from the inner cylinder(closed at one end)...to the outer cylinder(closed) and then through the gap between the two cylinders, over the inner cylinder and then backwards to a catalysor and then out...the catalysor also has a OD and ID but the thickness is not required to be meshed(only geometry)..so how do i exclude it from blocking(the circular thickness)?i create surfaces for each gap present...air flows in through a hole in the outer cylider,then through a hole in the inner cylinder...how do i get these 2 grids together(i make an o-grid for these 3 holes)?how do i split?do i make a block independently instead of splitting to get blocks for the holes?hope u can help me out...