[Gmsh] finding problem defining Ruled surface

[Osman Amin]

Hello, 
I am quite new in dealing with Gmsh software. I was going through the tutorial concerning flow around a cylinder (3d flow). I am willing to make a domain including channel surrounding a cylinder where the channel has an asymmetric configuration (lower half has smaller height than the upper half). Since the mesh generation technique in Gmsh is to first define the 2d surfaces and then extrude those into 3d volumes, I am having some problem in defining those meshing surfaces using 'Ruled Surface' command. The error that I am getting while trying to read the .geo file
 using Gmsh says - "wrong definition for ruled surface 9 - 1 borders instead of 3 or 4'. I am attaching the model.geo file with this email. I would be very much grateful if someone would help me in this respect. 

with regards, 
Amin
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