Why should an ideal fluid be incompressible?

[KingDaniel]

Hi,

I read that an ideal fluid needs to be frictionless and incompressible.
Please explain why, especially the incompressible part?

Thanks

 

[boneh3ad]

It makes their mathematical treatment substantially easier.

 

[Lok]

Hi,

I read that an ideal fluid needs to be frictionless and incompressible.
Please explain why, especially the incompressible part?Thanks

The bulk modulus of most materials is very high compared to usual pressures, resulting in insignificant compression of most materials. Solids usually are even more incompressible than liquids. Wiki the bulk modulus to get a feel for the forces involved.

 

[cjl]

As boneh3ad said, "ideal", in the context of a lot of math and science isn't saying that we wish real fluids behaved like that, it's about making assumptions/simplifications that make analysis easier (or in some cases, that make analysis possible at all). Compressibility dramatically increases the difficulty of fluid dynamics, so if you can ignore it, it makes a lot of sense to do so.

 

[boneh3ad]

As my PhD advisor often said, an ideal fluid is an 18-year-old, single malt Scotch whisky.

 

[cjl]

I think that's a definition I can get behind.