Flip Normals cannot be found in GUI

I want to model an internal pipe flow. I used a cylinder form primitives. As it is shown in the figure attached, the normals direction are towards the outside region which is not what I need.
In MFiX tutorial of modeling 3D cylindrical FB, it is mentioned that we need to check “Flip STL Normals” in the “mesher sub-pane.” I do not see this icon. This icon is not also located in Geometry pane.
What should I do?
BTW, Do we need to do anything with the normal direction of the mass inflow and the pressure outflow?

Hello, I note that the figure is a closed cylinder and not a pipe. This 3D figure has a “solid” interior (it has neither a solid nor a fluid phase). In that case, you need to have “surface” and not “solid” for the geometry, which is that you need.

I recommend using two cylinders of radio r1> r2, get their “difference” and you will get a pipe of radius r1 and with a thickness [r1, r2]. I also recommend for more advanced figures to create your .stl figure with an external program e.g. tinkercad, and then import it into mfix, the process is the same.

You asked about flip normals, and this can be seen in the geometry section

I hope I’ve been helpful,
Best Regards,

Thank you for your response… But I have seen the tutorial that has used the cylinder to model a fluidized bed… Why cannot I modify the boundary condition and the initial condition to make it a pipe?
And also, the pane that you sent its picture, I do not have the “Flip Normal” botton!!!???

What version of MFiX?

In the filter list, select the reverse sense, you can use that to flip normals as well.