Compressible vs. Incompressible Flow Equations

In summary, the conversation is about using fluid dynamics to understand compressed air systems. The speaker is studying incompressible fluid flow and wonders if standard equations can be used for systems with a working pressure of 7 bar without compensating for changing densities. The other person responds that it depends on the speed of the air and the range of pressures, and without more information, it's impossible to determine if incompressible equations will suffice for the speaker's purposes.
  • #1
fonz
151
5
As a private study I'm trying to figure out fluid dynamics applied to compressed air systems. Most of the material I am studying considers only incompressible fluid flow. From what I understand about the differences between compressible and incompressible flow in terms of the equations it only becomes significant when the mach number reaches about 0.3

In my systems I'm dealing with working pressures of no greater than 7 bar. Can apply standard equations to my calculations without having to compensate for changing densities due to pressure?
 
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  • #2
That depends entirely on how fast the air may move in your system and the range of pressures you plan to operate in. You haven't really described anything in enough detail to know that.
 
  • #3
At pressures of up to 7 bar, you could very easily have flow choking in places (in other words, locations in the flow where M = 1), so with the information provided, it's impossible to say whether incompressible equations will suffice or not for your purposes.
 

What is the difference between compressible and incompressible flow equations?

Compressible flow equations are used to describe the behavior of fluids that can be compressed, such as gases. Incompressible flow equations are used for fluids that cannot be compressed, such as liquids.

What types of flows are described by compressible and incompressible flow equations?

Compressible flow equations are typically used for high-speed flows, such as supersonic or hypersonic flows. Incompressible flow equations are used for low-speed flows, such as those encountered in everyday life.

What are some examples of compressible and incompressible fluids?

Examples of compressible fluids include air, natural gas, and steam. Examples of incompressible fluids include water, oil, and blood.

How are compressible and incompressible flow equations different mathematically?

Compressible flow equations take into account the changes in density and pressure of the fluid, while incompressible flow equations assume a constant density. This leads to different mathematical formulations and solutions.

When should I use compressible or incompressible flow equations in my research?

The choice between compressible and incompressible flow equations depends on the specific properties and behaviors of the fluid being studied. Generally, compressible flow equations are used for high-speed and low-density flows, while incompressible flow equations are used for low-speed and high-density flows.

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