2D axisymmetric model for concentric pipe.
I am modelling flow between two pipes(concentric pipe). Fluid flows only between the outer and inner tube. the space inside the inner tube would be just void. I would want to make 2D Axisymmetric model as shown in the figure that i uploaded.
As the axis is not in touch with the inner tube wall. I can not select a geometry to set as axis boundary. So currently filled the void with a rectangle geometry and assigned mesh and then select the wall that is in touch with x axis as rotation axis. It seems not efficient as the mesh in void area is not necessary in calculation. Is there any method to make 2D Axisymmetric model like this without generating a goemetry or mesh in the void area?