TikZ 中的轮廓绘制

Question

我正在尝试用 LateX 绘制以下图像， 但有些部分缺失了。我无法在圆弧上添加箭头，也不知道如何在圆心添加 1/4。

我的代码如下：

\begin{tikzpicture}
[decoration={markings,
mark=at position 0.75cm with {\arrow[line width=1pt]{>}},
mark=at position 2cm with {\arrow[line width=1pt]{>}},
mark=at position -4cm with {\arrow[line width=1pt]{>}},
mark=at position -5.98cm with {\arrow[line width=1pt]{>}},
mark=at position -3cm with {\arrow[line width=1pt]{>}},
}
]
\path[draw,line width=0.8pt,postaction=decorate] (10:1) node[left] {} -- +(-5,0) node[above right] {$\lambda_0$} arc (5:349:0.5) -- +(5,0);
\end{tikzpicture}

Answer 1

\documentclass{article}
\usepackage{amsmath}
\usepackage{tikz}
\usetikzlibrary{arrows.meta, decorations.markings}
\begin{document}
\begin{tikzpicture}[myarr/.style={decorate,decoration={markings, mark=at position #1 with {\arrow[line width=1pt]{>}}}}]
    \def\Ra{1} % radius of circle
    \def\lena{5} % length of pipe
    \def\anga{7} % half angle of pipe
    \draw[thick] (0,0) node[] {$\dfrac{1}{4}$} ++(\anga:\Ra) ++(\lena,0) -- (\anga:\Ra) arc[start angle=\anga, end angle=360-\anga, radius=\Ra] -- ++(\lena,0);
    \foreach \x in {0.2,0.4,0.5,0.6,0.8}
    \path[myarr=\x] (\anga:\Ra) ++(\lena,0) -- (\anga:\Ra) arc[start angle=\anga, end angle=360-\anga, radius=\Ra] -- ++(\lena,0);
\end{tikzpicture}
\end{document}