This #ParametricDaily includes 4 variants of the same concept: the application of subdivision(s) to a 3D knot mesh pipe. The base mesh was created by sweeping a 4-edge section along a trefoil knot 3D curve.
The edges of the base section were divided into multiple, non-uniform segments, so the bridging operation that connects the different sections generates a mesh already divided into multiple quad polygons. The subsequent subdivisions use two components included in the Mesh+ free add-on.
The first two images use the Crumple subdivision. In the second case the Crumple operation is followed by an additional Catmull-Clark subdivision.
The third and fourth images use the Polyp effect (always included in Mesh+): in the fourth image it is applied multiple times.
The images are abstract but give a good idea about how to use these types of subdivisions for creating real world 3D models.