做个笔记
-
\begin{equation}
\frac{\mathrm{D}K}{\mathrm{D}t} = \frac{1}{2}\frac{\mathrm{D}|\mathbf{U}|^2 }{\mathrm{D}t}
= \frac{1}{2}\frac{\mathrm{D} u_i^2 }{\mathrm{D}t}
= \frac{1}{2} \left( \frac{\partial u_i^2}{\partial t} + \mathbf{U} \cdot \nabla u_i^2 \right) \
= u_i \frac{\partial u_i}{\partial t} + \mathbf{U} \cdot u_i \nabla u_i
= \frac{\mathrm{D} \mathbf{U}}{\mathrm{D} t} \cdot \mathbf{U}
\label{KK}
\end{equation}:sunglasses:
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$\mathrm{TV}=\sum_{i}^{}|\phi_{i+1}-\phi_{i}|$
