Description eulérienne

Mathematically to describe the properties of a fluid moving, two systems cohabit, one and the other presenting of the advantages in typical locations. It is of the Lagrangian Description and description eulérienne.

The description eulérienne consists in being placed in a fixed point of the medium being studied and observing the modifications of the properties of the fluid which ravels in this point.

Within the framework of this description, the local properties of the fluid are function of $\backslash \; overrightarrow\; \{X\}$ and of T, and the same property, measured in the same point $\backslash \; overrightarrow\; \{X\}$ at two different times corresponds to two distinct particles Fluides.

It is the description which one generally uses in the problems of dynamics of the fluids, because it makes it possible to easily calculate the space variation of a property of the fluid at time T. The derivative partial of the density $\backslash \; frac\; \{\backslash \; partial\; \backslash \; rho\; (\backslash \; overrightarrow\; \{x\text{'}\},\; you)\}\{\backslash \; partial\; X\}$ is then the measurement of the rate of modification of the density around the point $\backslash \; overrightarrow\; \{x\text{'}\}$, at time you fixed, as one could obtain it by taking a photograph of the density of the flow then while deriving compared to the space variable.

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