alleryStart learning →The CONSERVATION OF MASS equation for an incompressible fluid ($\rho$ = const) is:
A$\nabla \cdot \mathbf{u} = 0$ (divergence-free velocity field)
B$\rho \mathbf{u} = 0$
C$\nabla \rho = 0$
D$\partial u/\partial t = 0$
Answer & Solution
Correct answer: A. $\nabla \cdot \mathbf{u} = 0$ (divergence-free velocity field)
**General mass conservation:** $\partial \rho/\partial t + \nabla \cdot (\rho \mathbf{u}) = 0$.
For incompressible flow ρ = const: $\nabla \cdot \mathbf{u} = 0$.
The velocity field has zero divergence — fluid cannot accumulate.
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