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Continuity Equation

From the conservation of mass in a closed system we can write down

Δm1 = Δm2

or                     A1 V1 P1 Δt = A2 V2 P2 Δt

or                     A1 V1 P1 = A2 V2 P2

A, V, p represent area, velocity and density. Subscripts 1 & 2 are used to indicate the parameters at section (1-1) and (2 – 2).

Equation (4.14) is known as continuity equation applicable to both compressible and incompressible fluids.

For incompressible fluid

P1 = P2

Equation (4.14) reduces to

A1 V1 = A2 V2