LaTeX 中的长子方程

Question

我正在使用 amsmath 包，在子方程环境中我有以下方程组

\begin{subequations}
\begin{align}
&\rho\left(u\frac{\partial u}{\partial x}+v\frac{\partial u}{\partial r}\right)=-\frac{\partial P}{\partial x}+\frac{M^2_\infty}{Re}\frac{1}{r}\frac{\partial}{\partial r}\left(\mu r\frac{\partial u}{\partial r}\right)\\
&\rho\left(u\frac{\partial h}{\partial x}+v\frac{\partial h}{\partial r}\right)=\rho\left(u\frac{\partial P}{\partial x}+v\frac{\partial P}{\partial r}\right)+\frac{M^2_\infty}{Re\dot Pr}\frac{1}{r}\frac{\partial}{\partial r}\left(\mu r\frac{\partial h}{\partial r}\right)+\frac{M^2_\infty}{Re}\mu\left(\frac{\partial u}{\partial r}\right)^2
\end{align}
\end{subequations}

使用此代码，第二个方程的引用被推到下面一行。我想弄清楚的是如何发送

+\frac{M^2_\infty}{Re}\mu\left(\frac{\partial u}{\partial r}\right)^2

到另一行，使其与等号对齐，但不要获得其自己的等式引用。

有任何想法吗？

Answer 1

使用split环境，它的工作原理如下align

\begin{subequations}
\begin{align}
  \rho\left(u\frac{\partial u}{\partial x}+v\frac{\partial u}{\partial r}\right)
  &= -\frac{\partial P}{\partial x} +
  \frac{M^2_\infty}{Re}\frac{1}{r}\frac{\partial}{\partial r}\left(\mu
    r\frac{\partial u}{\partial r}\right)\\ 
  \begin{split}
    \rho\left(u\frac{\partial h}{\partial x} + v \frac{\partial h}{\partial r}
    \right) &= \rho \left( u\frac{\partial P}{\partial x} + v
      \frac{\partial P}{\partial r} \right) \\
    &\quad{}+\frac{M^2_\infty}{Re\dot Pr} \frac{1}{r}\frac{\partial}{\partial r}
    \left(\mu r\frac{\partial h}{\partial r} \right) + \frac{M^2_\infty}{Re} \mu
    \left( \frac{\partial u}{\partial r}\right)^2
  \end{split}
\end{align}
\end{subequations}