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Incompressible Flow

A fluid, gas or plasma is said to be incompressible if
\begin{displaymath}
\nabla \cdot {\bf v} = 0.
\end{displaymath} (2.7)

Thus, the density of a fluid element does not vary as it moves with the flow so that
\begin{displaymath}
{D\rho \over Dt} = 0.
\end{displaymath} (2.8)

$\nabla \cdot {\bf v} \ne 0$ implies that the fluid is compressible.

Prof. Alan Hood
2000-11-06