nI recommend you slice all bodies using 2 planes parallel to YZ. One plane will be 25 mm along +X from the top internal solid wall. Another plane will be 25 mm along -X from the bend at the bottom of the tube.nThat will create a center block that has perfectly sweepable solids. That will allow you to create a low node count mesh because you can make the element size large in the X direction while it can be small in the Y and Z directions to capture the boundary layers in the water and air on the tube surfaces.nThe top and bottom blocks are a much smaller volume and can be meshed with tet elements.nIn all three blocks, you want inflation layers in the air on the tube OD and in the water on the tube ID.n