Headers in thesis

Question

I use a template with a documentclass{book} for my thesis, but for some reson the page numbering is messed up, in some pages numbers are in the middle of the page (as it should be) and in some pages, they are at the top of the page. So I fixed this with \usepackage{fancyhdr} and \pagestyle{fancy}, but now headers are messed, for example: Here is a "main.tex" code example:

\documentclass[12pt,a4paper,oneside,onecolumn]{book}
\usepackage[letterpaper, portrait]{geometry}
\usepackage{lipsum}
%SET AVERAGE MARGIN
\geometry{
left={4cm},
right={2cm},
top={1.5cm},
bottom={2.5cm},
}
\usepackage{layout}
\usepackage{fancyhdr}
\usepackage{libertine}
\usepackage{courier}
\usepackage[utf8x]{inputenc}
\usepackage[hebrew,english]{babel}
\usepackage[longnamesfirst,square,numbers,comma,sort&compress]{natbib}
\usepackage{titlesec}
\usepackage{float}
\usepackage{graphicx,caption}
\usepackage{amsmath}
\usepackage{mathpazo}
\usepackage{datetime}
\usepackage{hyperref}
\usepackage{bookmark}
%
\usepackage{float}
\usepackage{xcolor}
\usepackage{amssymb}
\usepackage{eufrak} 
\usepackage{accents} 
\usepackage{mathtools}
\usepackage{nicematrix}



\newcommand*{\bfrac}[2]{\genfrac{\lbrace}{\rbrace}{0pt}{}{#1}{#2}} %bar free fraction
\usepackage{romannum} %Roman numerals
\usepackage{bm}
%\addbibresource{ref.bib} %Imports bibliography file

\setlength{\parindent}{0pt}
\setlength{\parskip}{5pt}

\titleformat{\chapter}[hang]{\bf\huge}{\thechapter}{2pc}{}
\title{Thesis Template}

\begin{document}
%\layout


\include{cover}
\include{cover_heb}
\include{cover_sig}

\frontmatter
\pagestyle{fancy}

\include{Chapters/abstract_heb}
\include{Chapters/abstract}
\include{Chapters/table_of_abb}
\include{Chapters/acknowledgements}

\tableofcontents
\include{Chapters/table_of_symbols}
\listoffigures
\listoftables


\mainmatter
\pagestyle{fancy}

\input{Chapters/introduction}
\input{Chapters/previous_work}
\input{Chapters/Metasurface_analysis}
\input{Chapters/research_question}
\input{Chapters/methods}
\input{Chapters/results}
\input{Chapters/conclusion}

\section{}
\bibliographystyle{IEEEtran}
\bibliography{ref}

\end{document}

Any help is appreciated.

Answer 1

Something like this (that the added code is commanted with %here) could solve your problems (about the header).

\documentclass[12pt,a4paper,oneside,onecolumn]{book}
\usepackage[letterpaper, portrait]{geometry}
\usepackage{lipsum}
%SET AVERAGE MARGIN
\geometry{
left={4cm},
right={2cm},
top={1.75cm}, %here
bottom={2.5cm},
head={1.5cm}, %here
includehead %here
}
\usepackage{layout}
\usepackage{fancyhdr}
\usepackage{libertine}
\usepackage{courier}
\usepackage[utf8x]{inputenc}
\usepackage[hebrew,english]{babel}
\usepackage[longnamesfirst,square,numbers,comma,sort&compress]{natbib}
\usepackage{titlesec}
\usepackage{float}
\usepackage{graphicx,caption}
\usepackage{amsmath}
\usepackage{mathpazo}
\usepackage{datetime}
\usepackage{hyperref}
\usepackage{bookmark}
%
\usepackage{float}
\usepackage{xcolor}
\usepackage{amssymb}
\usepackage{eufrak} 
\usepackage{accents} 
\usepackage{mathtools}
%\usepackage{nicematrix}
\fancyhead[l]{} %here
\fancyhead[r]{} %here
\fancyhead[c]{\parbox[b]{\textwidth}{\parbox[b]{0.45\linewidth}{\rightmark}\hspace{\fill}\parbox[b]{0.45\linewidth}{\null\hfill\leftmark}}} %here

\newcommand*{\bfrac}[2]{\genfrac{\lbrace}{\rbrace}{0pt}{}{#1}{#2}} %bar free fraction
\usepackage{romannum} %Roman numerals
\usepackage{bm}
%\addbibresource{ref.bib} %Imports bibliography file

\setlength{\parindent}{0pt}
\setlength{\parskip}{5pt}

\titleformat{\chapter}[hang]{\bf\huge}{\thechapter}{2pc}{}
\title{Thesis Template}

\begin{document}
%\layout


\include{cover}
\include{cover_heb}
\include{cover_sig}

\frontmatter
\pagestyle{fancy}


\tableofcontents

\listoffigures
\listoftables


\mainmatter
\pagestyle{fancy}

\chapter{A Chapter}
\section{A section with a big name}
\newpage
\section{Another section with a much bigger name}


\end{document}

EDIT

In order to remove the section header and keep only the chapters, try like this instead: (Some un-needed code but this way you will be flexible in changes)

\fancyhead[c]{\parbox[b]{\textwidth}{\leftmark}} %here