| Abstract: | A fluid flow control device comprising an insert body having a first portion with a first permeability and second portion with a second permeability that is different from the first permeability. The insert body can be shaped for sealing insertion into a fluid flow structure for fluid flow therethrough. The first portion and the second portion can be arranged in the insert body to cause uniform fluid flow velocity of fluid in the fluid flow structure at an exit of the insert body when the fluid passes through the first portion and the second portion when the insert body is placed inside the fluid flow structure. |