Governing Equations
The governing equations of fluid dynamics and heat transfer are the mathematical and physical statements of the three famous conservation laws of physics:
  1. ”The mass of a fluid is conserved”
  2. ”The rate of change of momentum equals the sum of the forces on a fluid particle (Newton’s second law)”
  3. ”The rate of change of energy is equal to the sum of the rate of heat addition to and the rate of work done on a fluid particle (first law of thermodynamics)”
The behaviors of fluid will be described in terms of macroscopic properties such as temperature, pressure, velocity and density of fluid as well as space and time derivatives. The fluid element for derivation the conservation laws of physics will be in a 3 dimensional Cartesian coordinates as explained in Figure 3 that inserted below;