problem about uniting some volumes
 

Greetings,

Well, I'm new here and also to CFD..

My final project is using CFD...

Imagine that a cylinder (pipe) has a bend 90 degree...

and I'm supposed to put 4 small cylinders into the big cylinder(pipe)...

If we cut the pipe the cross section area would be a circle...

so the position of the 4 small cylinders would be at the top, bottom, left, and right at the arc of the circle.

the problem is the uniting process is successfully done for the 2 cylinder which is at left and right..but it turns disappointing when I'm trying to unite the top an bottom..I hope the readers are understand since the problem might be blurry to you..thank you..