Why water compressibility is neglicable

[bigbrother]

can anyone help me to have simple definition for compressibility and oil compressibility and why water compressibility is neglicable and for synthetic oils what is the effect of compressibilit on them compared to wter and diesel

 

[FredGarvin]

Compressibility can be looked at as the change in volume with change in pressure. Or, similarly, you can look at in terms of change in density with respect to pressure.

If you look at the density of air over a range of pressures, you'll see that it doesn't take much pressure to have a significant affect on the density. However water's density will only vary about 2% up to pressures of about 7000 psi.

It is a judgment call on whether or not to use the incompressible assumption or not.

 

[bigbrother]

many thanks for your response but kindly could you advice about the oil comperssibility compared to water

 

[FredGarvin]

They are both incompressible up to some very large pressures. I'll see if I can't dig some actual numbers up.

 

[FredGarvin]

Here you go:
http://www.engineeringtoolbox.com/bulk-modulus-elasticity-d_585.html

 

[bigbrother]

many thanks for this valuable link
but could you please confirm with me what i understood from this is that oil comperssibility is the same as water,no great diferrences between them
is that true