[Jessica@123]

I'm facing this really annoying problem with fluent where I’m trying to create a plane at the throat of a bell nozzle engine, which is inclined at an angle relative to the X-axis. My geometry is a 3D half-model of a bell nozzle, cut along the XY plane, with an external domain to represent the environment. This setup shows then half of the engine from the inlet to the nozzle exit (I've half of inlet, throat and nozzle exit) inclined at an angle.

When I create a plane using the default XY, YZ, or ZX orientations and apply an area-weighted average, the results are not accurate because the plane intersects both the nozzle geometry and the external domain. As a result, the values include contributions from the environment, which I want to avoid.

How can I create a surface or plane exactly at the throat cross-section and at the nozzle exit — aligned with the nozzle's inclination — such that it only includes the internal flow domain of the nozzle and excludes the external environment?