Latex 代码

\begin{figure}
    \begin{subfigure}[b]{0.32\textwidth}
        \centering
        \resizebox{\linewidth}{!}{
            \begin{tikzpicture}
                \coordinate (o) at (0,0);
                \coordinate (Si) at (2.5,2.5);
                \coordinate (x) at (1,0);
                \draw[->] (0,0) -- (3,0) node[right] {$x$};
                \draw[->] (0,0) -- (0,3) node[above] {$t$};
                \draw[-] (o) -- (Si) node[right] {$S_i$};
                \draw[->] (0.5,2) -- (2,2.3) node[midway, above] {$U_L$};
                \draw[->] (2,0.5) -- (2.3,2) node[midway, right] {$U_R$};
                \node[below left] {$o$};
            \end{tikzpicture}
        }
        \caption{shock wave}
        \label{fig:shock_wave_1}
    \end{subfigure}
    \begin{subfigure}[b]{0.32\textwidth}
        \centering
        \resizebox{\linewidth}{!}{
            \begin{tikzpicture}
                \coordinate (o) at (0,0);
                \coordinate (Si) at (2.5,2.5);
                \coordinate (x) at (1,0);
                \draw[->] (0,0) -- (3,0) node[right] {$x$};
                \draw[->] (0,0) -- (0,3) node[above] {$t$};
                \draw[dashed] (o) -- (Si) node[right] {$S_i$};
                \draw[->] (0.7,1.5) -- (1.7,2.5) node[midway, left] {$U_L$};
                \draw[->] (1.5,0.7) -- (2.5,1.7) node[midway, right] {$U_R$};
                \node[below left] {$o$};
            \end{tikzpicture}
        }
        \caption{contact discontinuity}
        \label{fig: contact_discontinuity_1}
    \end{subfigure}
    \begin{subfigure}[b]{0.32\textwidth}
        \centering
        \resizebox{\linewidth}{!}{
            \begin{tikzpicture}
                \coordinate (o) at (0,0);
                \coordinate (Si1) at (1.8,2.7);
                \coordinate (Si2) at (2.2,2.7);
                \coordinate (Si3) at (2.5,2.5);
                \coordinate (Si4) at (2.7,2.2);
                \coordinate (Si5) at (2.7,1.8);
                \coordinate (x) at (1,0);
                \draw[->] (0,0) -- (3,0) node[right] {$x$};
                \draw[->] (0,0) -- (0,3) node[above] {$t$};
                \draw[-] (o) -- (Si1) node[right] {};
                \draw[-] (o) -- (Si2) node[right] {};
                \draw[-] (o) -- (Si3) node[right] {};
                \draw[-] (o) -- (Si4) node[right] {};
                \draw[-] (o) -- (Si5) node[right] {};
                \draw[->] (0.5,1.5) -- (1.4,2.85) node[midway, left] {$U_L$};
                \draw[->] (1.5,0.5) -- (2.85,1.4) node[midway, right] {$U_R$};
                \node[below left] {$o$};
            \end{tikzpicture}
        }
        \caption{rarefaction wave}
        \label{fig:rarefaction_wave_1}
    \end{subfigure}
    \caption{Wave of Riemann problem}
    \label{fig:wave_of_riemann. $S_i$ is wave speed, $U_L,U_R$ are initial data states connected by a single wave.}
\end{figure}

输出：

绘图参考：

《Riemann Solvers and Numerical Methods for Fluid Dynamics》P84