text: Flow conditioners shown in fig.(a) can be grouped into following three types –
  * Those that eliminate swirl only (tube bundles)
  * Those that eliminate swirl and non-symmetry, but do not produce pseudo fully developed flow
  * Those that eliminate swirl and non-symmetry and produce pseudo fully developed flow (high-performance flow conditioners)
  Straightening devices such as honeycombs and vanes inserted upstream of the flow meter can reduce the length of straight pipe required. However, they produce only marginal improvements in measurement accuracy and may still require significant length of straight pipe, which a cramped installation site may not permit.
  A flow straightener, sometimes called a honeycomb, is a device used to straighten the air flow in a wind tunnel. It is a passage of ducts, laid along the axis of main air stream to minimize the lateral velocity components caused by swirling motion in the air flow during entry. The cross-section shapes of these "honeycombs" may be of square, circular and regular hexagonal cells.