[KevinW]

Hello everyone, I had a problem, and I really appreciate your help.
I am trying to simulate a flow around 2D airfoil. Shell mesh generation is done in the ICEM CFD, edit mesh->extrude mesh(layer=1, spacing=1), to convert it from 2D to 3D, which is required by CFX. The problem is when I import the mesh *.cfx5 to CFX-PRE, a boundary named "Default Domain Default" is alreay there with its command editor as follows:

FLOW: Flow Analysis 1
DOMAIN: Default Domain
&replace BOUNDARY: Default Domain Default
Boundary Type = WALL
Create Other Side = Off
Interface Boundary = Off
Location = AIRFOIL_BODY,IN,INFINITE_SURROUNDING,OUT,Primitive 2D,Primitive 2D A,Primitive 2D C,TOPSURFACE
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = No Slip Wall
END
WALL ROUGHNESS:
Option = Smooth Wall
END
END
END
END
END

Why is it there? And IT CAN NOT BE DELETED!WHY?
And what is Primitive 2D,Primitive 2D A,Primitive 2D C? Curves I forgot to put into any part?
Thank you in advance.

[ghorrocks]

This is just the default region using all boundaries. Define the boundaries you want using the mesh boundaries and it will be fine.

[KevinW]

I should see the "help" carefully.....This is what it says.Thank you all the same, Glenn.

14.1.*Default Boundary Condition
You should be familiar with the concept of primitive and composite regions before reading this section. If you are not, see Mesh Topology in CFX-Pre for details.
When a domain is created, all of the bounding 2D regions that are not used elsewhere are assigned to a default boundary condition that is created automatically. These regions can be considered as the boundary between the current domain and the rest of the "world". The boundary that is generated is given the name <Domain name> Default. When 2D primitives (or composites that reference them) are assigned to other boundary conditions and domain interfaces, they are removed from the <Domain name> Default boundary condition. The default boundary condition is a no-slip adiabatic wall, but this can be edited like any other boundary condition. Solid-world 2D primitives behave in a similar way.

Removing Regions from the Default Domain
Fluid-solid regions are initially contained in the <Domain Name> Default boundary condition. When a CFX-Solver input file is written, or a user-defined domain interface is created, any fluid-solid regions referenced by this interface are removed from the default boundary.
If every region is assigned to another boundary condition, the <Domain Name> Default boundary object will cease to exist. In such a case, if a boundary condition is subsequently deleted, the <Domain name> Default wall boundary will be recreated for the unspecified region. Because the <Domain name> Default wall boundary condition is controlled automatically, you should never need to explicitly edit its Location list.