In mesher subset, I could not see the option “External flow” instead only these (“Flip STL norms and Enable array re-indexing”) options are available. Why this issue?
The determination of which side the fluid is on depends on which why the STL normals are pointing. If you want the fluid on the outside of you STL, then make sure the normals are pointed out of the STL. So, if the normals are pointed the wrong direction, you can flip them either in the geometry section or by toggling Flip STL norms.
