Problems when I meshing a tube of I.D.=5cm and L=4m

When I mesh a tube (I.D.=5cm and L=4m) , the geometry is deformed (obviously, the simulation does not converge).
When I reduce the size of the tube, for example L = 1m, everything works correctly. Can someone suggest me something to improve this. Additionally, the particles that I will use in my simulation are Geldart A, so I must build a mesh with cells of at least 2 mm on each side.