Just some concepts to be familarised for fluid mechanics

[jasoncurious]

Hi guys, I am currently studying fluid mechanics. This is my first time doing the subject. I've been reading some books. Then I realised something:

 

1. Do we always have to use an annulus as a fluid element? What's so special about the ring? Was it because it's easier to analyse?

2. Regarding "head" (dimension L), is it easier to understand by expressing it in L?

 

Thank you.

[Enthalpy]

An annulus is used where the stream is expected to have a cylindrical symmetry. Sheets, disks... fit other cases better.

 

Head as a length: in a dam it's more expressive, in a turbofan not.

[jasoncurious]

Thanks. So, the "head" concept is something like a "conservation of height" thing?

[Enthalpy]

Fluids can convert pressure to speed and, often less efficiently, speed to pressure. Head expresses the sum of both, with the speed component converted with ideal efficiency to more pressure.

 

Pressure can be given as a water height if this is more expressive.