# Fluid

A fluid is a substance that deforms and changes position when put under stress. Fluids can be both liquids and gases.

## Fluid Types

**Compressibility Fluid**- When the density of the fluid changes with the application of external force.

**Ideal Fluid**- This assumes to have no viscosity, meaning no resistance or shear, and not compressable. In an ideal fluids there is uniform velocity distribution when flowing.

**Ideal Plastic Fluid**- A fluid, in which shear stress is more than the yield value and shear stress is directly proportional to the rate of shear strain.

**Incompressibility Fluid**- When the density of the fluid doesnâ€™t change with the application of external force.

**Newtonian Fluid**- This fluid's viscosity is constant no matter how much shear is applied for a constant temperature.

**non-Newtonian Fluid**- This is the opposite of Newtonian fluids and does not following Newton's law of viscosity. These fluids having variable viscosity when shear is applied.

**Real Fluid**- This fluid does not have uniform velocity distribution, it is compressable, shows finite viscosities and experience friction and turbulance in flow.

## Fluid Properties

Properties |
Gas |
Liquid |
Solid |

Compressibility | Yes | Low | No |

Density | Low | Moderate | High |

Expandability | Yes | Yes | No |

Intermolecule force strength | Weak | Moderate | Strong |

Particle Movement | Free movement | Free movement | No free movement |

Shape | Infinite | Infinite | Fixed |

Shear Resistance | Yes | Yes | No |

Viscosity | Low | Varies | No |

Volume | Infinite | Fixed | Fixed |