This tube was created using a spline. The issue is that the tube is bending over itself when the spline curvature is too abrupt. Are there any commands that would get rid of internal surfaces generated by this bend and make the tube a “perfect” solid object?
PS: I want to know if I can fix the geometry that I already have, not to recreate the tube from scratch.
Self-intersecting surfaces are not easy to deal with. The quick answer is if you explode that and Split up the pipe surface into separate sections, you will eventually be able to find the intersections and trim them out. It’s not something Rhino (or most software) can figure out itself.
Without further description, that’s questionable.
Is this tube for liquids? Gas? The inner of the bend is creating a sharp turn, bad for any case.
What’s “perfect”?
How will you manufacture this? Why does it need to have this shape?
Best fix? As you guessed, re-do from scratch with starting tube inner rail having a minimum curvature greater than the radius pipe.
Or, something like this:
finding and using the actual self-intersection is tricky and unreliable, imho
Or, if your pipe is following a symmetric rail (which is not the case in your picture)
you can split with a bisector plane:
