Hi , can u plz explain what is swirl ? i feel it is just like angular velocity.is it so?plz explain it?how it is deifnr in STARCD nikhil

it depends what type of swirl you are talking about. If you have an s shapped duct then swirl is a phenomina ecnountered at the exit of the duct. AS the flow travels round the first bend of the s an adverse pressure gradient is created as the fluid on the outside of the bend is travelling faster than that on the inside due to the increased distance it has to travel (greater diameter), this creates high pressure on the inside and low on the outside so the flow tends to start to travel across the duct. If another bend in the opposite direction is encoutered then the reverse happens and so you now have swirl which tends to propgate down the duct. The effect is less on a single bend but the pressure gradient still exists and so losses occur.