Cfrgtkky

I have some problems in spacing.
I just want to put equations in the text.
What I found is that the vertical spacing between the equation and text is not consistent.
Some is large and some is small. Both spacings above and below equation are not consistent.
How do I get consistent spacing in the entire thesis?
I can adjust spacing using vspace{baselineskip}.
But I am not sure the spacing is exactly the same or not. It doesnt seems good solution.
Here is my code.

documentclass[twoside]{utmthesis}

%According to the new manual, should not mixed single-side with two-side 

printing

usepackage{graphicx}

usepackage{url} 

%usepackage[pages=some]{background}

usepackage{lipsum}

usepackage{pdflscape}

usepackage{verbatim}

usepackage{textcomp}

usepackage{mhchem}

usepackage{amsmath} 

usepackage{listings}

usepackage{graphicx}

usepackage{mwe}

usepackage{xr}

usepackage{siunitx}

usepackage{float}

usepackage{subfig}

newsavebox{bigleftbox}

usepackage{tikz}

usepackage{nameref}

%usepackage[printonlyused]{acronym}

usepackage{romannum}

usetikzlibrary{shapes.geometric, arrows}

usepackage{natbib}

letcitecitep

bibliographystyle{utmthesis-authordate}



begin{document}

subsection{1D numerical modeling of the SI-engine}

vspace{baselineskip}

The numerical models and related equations applied in the 1D engine 

simulation are presented and briefly discussed.

subsubsection{Pipe}

vspace{baselineskip}

In one-dimension modeling of flow through the pipes, working fluid is 

assumed that it is flowing in one-direction, instead of three direction (X, 

Y, and Z). It seems plausible, as most fluid particles are moving mostly in 

longitudinal direction rather than radial direction of the pipe. A one- 

dimensional pipe flow is described by Euler equation which is given in 

conservation form below.



begin{equation} label{Euler}

frac{partial mathbf{U}}{partial t} + frac{partial mathbf{F(U)}} 

{partial x}= mathbf{S(U)}

end{equation}



$textbf{U}$ and $textbf{F}$ represent state vector and flux vector, 

respectively which are represented as follows.



begin{equation}

mathbf{U}= begin{pmatrix}

rho \

rho cdot u \

rho cdot bar{C_v} cdot T + frac{1}{2} cdot rho cdot u^2 \

rho cdot w_j end{pmatrix},,, , ,,, mathbf{F}= begin{pmatrix}

rho cdot u \

rho cdot u^2 + p \

rho cdot (E+p) \

rho cdot u cdot w_j  end{pmatrix}

end{equation}



With total energy, $E$ is given as below.



begin{equation} label{E}

begin{split}

E=rho cdot bar{C_v} cdot T + frac{1}{2} cdot rho cdot u^2

end{split}

end{equation}



The source term, $textbf{S}$ is divided into two different sub-source 

terms. 



begin{equation} label{S}

   mathbf{S(U)}= mathbf{S_A(F(U))} + mathbf{S_R(U)}

end{equation}



$mathbf{S_A}$ is the source term caused by axial changes in the pipe cross 

section.



begin{equation} label{Sa}

mathbf{S_A(F(U))}= - frac{1}{A} cdot frac{dA}{dx} cdot left(F + 

begin{pmatrix}

0 \

-p  \

0 \

0 

end{pmatrix} right)

end{equation}



$mathbf{S_R}$ is the source term taking into account homogeneous chemical 

reaction, friction, heat and mass transfer between gas and solid phase.



begin{equation} label{Sr}

mathbf{S_R(F(U))}= begin{pmatrix}

0 \

-frac{F_R}{V}  \

frac{q_w}{V} \

M W_j cdot left(sumlimits_{i}^{R_{hom}} nu_{i.j} cdot 

dot{r_i}right)end{pmatrix}

end{equation}



bibliography{reference}

end{document}

In order to increase the space around equations, you can use this answer, which redefines abovedisplayskip and so on. (And in order to increase space after section titles, you use this answer.) Empty lines end paragraphs and should not be used to change the spacing around the equations. You effectively say latex to start a new paragraph, and that's why the result is not as you want it to be.

documentclass[twoside]{article}

usepackage{amsmath}

% from https://tex.stackexchange.com/a/69665/121799

expandafterdefexpandafternormalsizeexpandafter{%

  normalsize  

  setlengthabovedisplayskip{4ex}

  setlengthbelowdisplayskip{4ex}

  setlengthabovedisplayshortskip{4ex}

  setlengthbelowdisplayshortskip{4ex}

}

usepackage{titlesec}

% from https://tex.stackexchange.com/a/108747/121799

titlespacing*{section}

{0pt}{3.5ex plus 1ex minus .2ex}{5.3ex plus .2ex}

titlespacing*{subsection}

{0pt}{3.5ex plus 1ex minus .2ex}{5.3ex plus .2ex}

begin{document}



subsection{1D numerical modeling of the SI-engine}

The numerical models and related equations applied in the 1D engine 

simulation are presented and briefly discussed.



subsubsection{Pipe}

In one-dimension modeling of flow through the pipes, working fluid is 

assumed that it is flowing in one-direction, instead of three direction (X, 

Y, and Z). It seems plausible, as most fluid particles are moving mostly in 

longitudinal direction rather than radial direction of the pipe. A one- 

dimensional pipe flow is described by Euler equation which is given in 

conservation form below.

begin{equation} label{Euler}

frac{partial boldsymbol{U}}{partial t} + frac{partial boldsymbol{F(U)}} 

{partial x}= boldsymbol{S(U)}

end{equation}

$textbf{U}$ and $textbf{F}$ represent state vector and flux vector, 

respectively which are represented as follows.

begin{equation}

boldsymbol{U}= begin{pmatrix}

rho \

rho cdot u \

rho cdot bar{C_v} cdot T + frac{1}{2} cdot rho cdot u^2 \

rho cdot w_j end{pmatrix};,quad boldsymbol{F}= begin{pmatrix}

rho cdot u \

rho cdot u^2 + p \

rho cdot (E+p) \

rho cdot u cdot w_j  end{pmatrix}

end{equation}

With total energy, $E$ is given as below.

begin{equation} label{E}

begin{split}

E=rho cdot bar{C_v} cdot T + frac{1}{2} cdot rho cdot u^2

end{split}

end{equation}

The source term, $textbf{S}$ is divided into two different sub-source 

terms. 

begin{equation} label{S}

   boldsymbol{S(U)}= boldsymbol{S_A(F(U))} + boldsymbol{S_R(U)}

end{equation}

$boldsymbol{S_A}$ is the source term caused by axial changes in the pipe cross 

section.

begin{equation} label{Sa}

boldsymbol{S_A(F(U))}= - frac{1}{A} cdot frac{mathrm{d}A}{mathrm{d}x} cdot left(F + 

begin{pmatrix}

0 \

-p  \

0 \

0 

end{pmatrix} right)

end{equation}

$boldsymbol{S_R}$ is the source term taking into account homogeneous chemical 

reaction, friction, heat and mass transfer between gas and solid phase.

begin{equation} label{Sr}

boldsymbol{S_R(F(U))}= begin{pmatrix}

0 \

-frac{F_R}{V}  \

frac{q_w}{V} \

M W_j cdot left(sumlimits_{i}^{R_{hom}} nu_{i.j} cdot 

dot{r_i}right)end{pmatrix}

end{equation}



end{document}