Hi , I am unable to understand

[extremechanical]

Hi ,
I am unable to understand the following concept:

It is said mach number less than 0.3 indicates the fluid is in compressible.
So is it that Mach Number Equal to 1 means fluid is highly compressible?
It is also said during choking of gas in compressor the fluid will reach mach number 1. What exactly it means ?

Can you please also explain what exact effect Mach number has on compressor?

 

[Compositepro]

I think the intent of such a statement is that at less than mach 0.3 you may treat the fluid as incompressible because the effects of compressiblility are small.

 

[MortenA]

I would say that most if these statements dosnt make much sence!

- If the fluid is a gas its compressible - but its also compressible at any other velcoty. But if its liqyuid its not compressible (for most concerns) af velocities less than mach 0.3
- Highly compressible? Whats this?
- Why (and how) whould you choke a compressor and where?

Wrt to pressure drop in e.g. an orifice (or in a valve which is like an adjustable orifice) then if the flow is "choked" then the mach no is 1 and at this stage the flow becomes indifferent to the downstream pressure. So decreasing the downstream pressure will not increase the flow rate (but increasing the upstream will)

Best regards, Morten

 

[rotw]

which Mach number is equal to 1 and where ?
At impeller eye?
Impeller peripheral Mach number?
Mach number calculated based on absolute velocity?

Peripheral Mach number can be > 1.0 at design point!