2. THEORETICAL FOUNDATIONS

2.1 Material balance

Start in a closed fluid-filled pipe. We realize the material balance between points 1 and 2:

- The mass flow m passing through the section S₁that goes through the same section S₂:

- We know that density is the relationship between mass flow (m) and volumetric flow (G):

- If the fluid is incompressible:

- The volumetric flow is related to the linear velocity of the fluid (u), and section perpendicular to the passage of fluid (S):

- Therefore:

-This is the equation of continuity, which can be also indicated how:

Where:

G = volumetric flow (m³/s).

m = mass flow (kg/s).

S = section perpendicular to the passage of fluid (m²).

u = linear velocity of the fluid (m/s).

ρ = density of the fluid (kg/m³).