Fluids

What is a fluid?

A fluid cannot resist shear stress by static deflection, they are liquids and gasses.

Properties of a Fluid

• Temperature: kinetic energy of molecules
• Pressure: momentum change
• Density: $\frac{mass}{volume}$

Fluids also have Extensive and Intensive Properties.

Primary Dimensions:

• mass [m]
• length [L]
• time [T]

We analyze fluids using dimensional analysis

We can make a non-dimensional Strouhal Number which govern oscillating flow $\frac{FD}{v}=\frac{\frac{1}{T}\cdot L}{\frac{L}{T}}$

Fluid Parcels

A small identifiable amount of fluid
This parcel has a history of properties, temperature, velocity and is closely related to a Lagrangian perspective

Perspectives

The different perspectives we are concerned with are:

• Lagrangian: Following individual parcels as they move through space and time
• Eulerian: At a fixed location in space looking at the parcels passing by

We analyze fluids in Scalar Fields and Vector Fields