diff --git a/Project1/LyX/#Abstract.lyx# b/Project1/LyX/#Abstract.lyx# deleted file mode 100644 index ccbdddca55fd4ca15590f76335a7f7b9835021be..0000000000000000000000000000000000000000 --- a/Project1/LyX/#Abstract.lyx# +++ /dev/null @@ -1,114 +0,0 @@ -#LyX 2.4 created this file. For more info see https://www.lyx.org/ -\lyxformat 620 -\begin_document -\begin_header -\save_transient_properties true -\origin unavailable -\textclass IEEEtran-CompSoc -\use_default_options true -\maintain_unincluded_children no -\language american -\language_package default -\inputencoding utf8 -\fontencoding auto -\font_roman "default" "default" -\font_sans "default" "default" -\font_typewriter "default" "default" -\font_math "auto" "auto" -\font_default_family default -\use_non_tex_fonts false -\font_sc false -\font_roman_osf false -\font_sans_osf false -\font_typewriter_osf false -\font_sf_scale 100 100 -\font_tt_scale 100 100 -\use_microtype false -\use_dash_ligatures true -\graphics default -\default_output_format default -\output_sync 0 -\bibtex_command default -\index_command default -\float_placement class -\float_alignment center -\paperfontsize default -\spacing single -\use_hyperref false -\papersize default -\use_geometry true -\use_package amsmath 1 -\use_package amssymb 1 -\use_package cancel 1 -\use_package esint 1 -\use_package mathdots 1 -\use_package mathtools 1 -\use_package mhchem 1 -\use_package stackrel 1 -\use_package stmaryrd 1 -\use_package undertilde 1 -\cite_engine basic -\cite_engine_type default -\biblio_style plain -\use_bibtopic false -\use_indices false -\paperorientation portrait -\suppress_date false -\justification true -\use_refstyle 1 -\use_formatted_ref 0 -\use_minted 0 -\use_lineno 0 -\index Index -\shortcut idx -\color #008000 -\end_index -\leftmargin 2.5cm -\topmargin 2.5cm -\rightmargin 2.5cm -\bottommargin 2.5cm -\secnumdepth 3 -\tocdepth 3 -\paragraph_separation indent -\paragraph_indentation default -\is_math_indent 0 -\math_numbering_side default -\quotes_style english -\dynamic_quotes 0 -\papercolumns 1 -\papersides 1 -\paperpagestyle default -\tablestyle default -\tracking_changes false -\output_changes false -\change_bars false -\postpone_fragile_content true -\html_math_output 0 -\html_css_as_file 0 -\html_be_strict false -\docbook_table_output 0 -\docbook_mathml_prefix 1 -\end_header - -\begin_body - -\begin_layout Abstract -A frequent reason for neurodegenerative diseases is the swelling of axons (nerve cells). - This swelling is often caused by traffic jams in intracellular traffic. - The purpose of this work is to inspect a mathematical model, - combining diffusive and advective transport behavior, - for intracellular traffic. - This coupled model describes the natural movement of free particles and particles riding on microtubules towards and away from the neuron body and the interaction between these different particles. - -\end_layout - -\begin_layout Abstract -This work aims to under -\end_layout - -\begin_layout Keywords -Some Keywords -\end_layout - -\end_body -\end_document diff --git a/Project1/LyX/#Implementation.lyx# b/Project1/LyX/#Implementation.lyx# deleted file mode 100644 index 20761ee55b3282d788293738cc5e39c2e7ad342c..0000000000000000000000000000000000000000 --- a/Project1/LyX/#Implementation.lyx# +++ /dev/null @@ -1,268 +0,0 @@ -#LyX 2.4 created this file. For more info see https://www.lyx.org/ -\lyxformat 620 -\begin_document -\begin_header -\save_transient_properties true -\origin unavailable -\textclass IEEEtran-CompSoc -\use_default_options true -\maintain_unincluded_children no -\language english -\language_package default -\inputencoding utf8 -\fontencoding auto -\font_roman "default" "default" -\font_sans "default" "default" -\font_typewriter "default" "default" -\font_math "auto" "auto" -\font_default_family default -\use_non_tex_fonts false -\font_sc false -\font_roman_osf false -\font_sans_osf false -\font_typewriter_osf false -\font_sf_scale 100 100 -\font_tt_scale 100 100 -\use_microtype false -\use_dash_ligatures true -\graphics default -\default_output_format default -\output_sync 0 -\bibtex_command default -\index_command default -\float_placement class -\float_alignment class -\paperfontsize default -\spacing single -\use_hyperref false -\papersize default -\use_geometry false -\use_package amsmath 1 -\use_package amssymb 1 -\use_package cancel 1 -\use_package esint 1 -\use_package mathdots 1 -\use_package mathtools 1 -\use_package mhchem 1 -\use_package stackrel 1 -\use_package stmaryrd 1 -\use_package undertilde 1 -\cite_engine basic -\cite_engine_type default -\biblio_style plain -\use_bibtopic false -\use_indices false -\paperorientation portrait -\suppress_date false -\justification true -\use_refstyle 1 -\use_formatted_ref 0 -\use_minted 0 -\use_lineno 0 -\index Index -\shortcut idx -\color #008080 -\end_index -\secnumdepth 3 -\tocdepth 3 -\paragraph_separation indent -\paragraph_indentation default -\is_math_indent 0 -\math_numbering_side default -\quotes_style english -\dynamic_quotes 0 -\papercolumns 1 -\papersides 1 -\paperpagestyle default -\tablestyle default -\tracking_changes false -\output_changes false -\change_bars false -\postpone_fragile_content true -\html_math_output 0 -\html_css_as_file 0 -\html_be_strict false -\docbook_table_output 0 -\docbook_mathml_prefix 1 -\end_header - -\begin_body - -\begin_layout Section -Implementation -\end_layout - -\begin_layout Standard -All the following examples, - visualizations and the discussed implementation can be found in the reproducability repository for this project (see -\begin_inset CommandInset citation -LatexCommand cite -key "Repository" -literal "false" - -\end_inset - -). - All the implementations are done with the Python programming language, - mainly with the numpy package for vector operations and matplotllib for visualizations. - Furthermore, - there is an additional implementation using the open-source software FEniCSx -\begin_inset Foot -status open - -\begin_layout Plain Layout -FEniCSx: - -\begin_inset Flex URL -status open - -\begin_layout Plain Layout - -https://fenicsproject.org/ -\end_layout - -\end_inset - - -\end_layout - -\end_inset - -, - which utilizes the Finite Element Method. - This software was used to check the Python implementation and the correctness of the method. -\end_layout - -\begin_layout Subsection -Convergence Analysis -\end_layout - -\begin_layout Standard -A convergence analysis was performed to ensure the numerical implemenation's correctness for the two uncoupled advection equations. - The solutions for different grid sizes are compared to the analytical solution. - To interpret the convergence of the numerical method, - a relevant error measure is introduced. - The -\begin_inset Formula $\mathcal{L}_{1}$ -\end_inset - - norm and its relative counterpart are calculated as -\end_layout - -\begin_layout Standard -\begin_inset Formula -\begin{align} -\mathcal{L}_{1}(u) & =\int_{\Omega}\left|u-u_{\text{exact}}\right|d\Omega\\ -\mathcal{L}_{1,\text{rel}}(u) & =\frac{\mathcal{L}_{1}(u)}{\int_{\Omega}\left|u_{\text{exact}}\right|d\Omega} -\end{align} - -\end_inset - -For the convergence analysis, - the relative error norm -\begin_inset Formula $\mathcal{L}_{1,\text{rel}}$ -\end_inset - - will be used. - For the convergence analysis the default parameter (see -\begin_inset CommandInset ref -LatexCommand ref -reference "subsec:ListOfVariables" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - -) were used. - The grid length is chosen from -\begin_inset Formula $\Delta x\in\{2.0,0.2,0.02,0.002\}$ -\end_inset - -. - The cfl-condition was checked for every grid size. - If the condition was not fulfilled, - the time step size was reduced iteratively, - until it was fulfilled. -\end_layout - -\begin_layout Standard -\begin_inset Float figure -placement document -alignment document -wide false -sideways false -status open - -\begin_layout Plain Layout - -\end_layout - -\begin_layout Plain Layout -\begin_inset Graphics - filename Figures/Convergence_L1.pdf - width 100text% - -\end_inset - - -\begin_inset Caption Standard - -\begin_layout Plain Layout -Convergence -\begin_inset CommandInset label -LatexCommand label -name "fig:Convergence" - -\end_inset - - -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Plain Layout - -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Standard -Figure -\begin_inset CommandInset ref -LatexCommand ref -reference "fig:Convergence" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - - visualizes the -\begin_inset Formula $\mathcal{L}_{1,\text{rel}}$ -\end_inset - - error for both, - the particles moving in positive and negative direction. - Both error converge approximately with order -\begin_inset Formula $\frac{1}{2}$ -\end_inset - -. - As the used finite difference stencil for the spatial derivative -\begin_inset Formula $(n_{\pm})_{x}$ -\end_inset - - is of first order -\end_layout - -\end_body -\end_document diff --git a/Project1/LyX/#Introduction.lyx# b/Project1/LyX/#Introduction.lyx# deleted file mode 100644 index de1f379ab83b447b028245135fa267afe2a2b78a..0000000000000000000000000000000000000000 --- a/Project1/LyX/#Introduction.lyx# +++ /dev/null @@ -1,550 +0,0 @@ -#LyX 2.4 created this file. For more info see https://www.lyx.org/ -\lyxformat 620 -\begin_document -\begin_header -\save_transient_properties true -\origin unavailable -\textclass IEEEtran-CompSoc -\use_default_options true -\maintain_unincluded_children no -\language american -\language_package default -\inputencoding utf8 -\fontencoding auto -\font_roman "default" "default" -\font_sans "default" "default" -\font_typewriter "default" "default" -\font_math "auto" "auto" -\font_default_family default -\use_non_tex_fonts false -\font_sc false -\font_roman_osf false -\font_sans_osf false -\font_typewriter_osf false -\font_sf_scale 100 100 -\font_tt_scale 100 100 -\use_microtype false -\use_dash_ligatures true -\graphics default -\default_output_format default -\output_sync 0 -\bibtex_command default -\index_command default -\float_placement class -\float_alignment center -\paperfontsize default -\spacing single -\use_hyperref false -\papersize default -\use_geometry false -\use_package amsmath 1 -\use_package amssymb 1 -\use_package cancel 1 -\use_package esint 1 -\use_package mathdots 1 -\use_package mathtools 1 -\use_package mhchem 1 -\use_package stackrel 1 -\use_package stmaryrd 1 -\use_package undertilde 1 -\cite_engine basic -\cite_engine_type default -\biblio_style plain -\use_bibtopic false -\use_indices false -\paperorientation portrait -\suppress_date false -\justification true -\use_refstyle 1 -\use_formatted_ref 0 -\use_minted 0 -\use_lineno 0 -\index Index -\shortcut idx -\color #008000 -\end_index -\secnumdepth 3 -\tocdepth 3 -\paragraph_separation indent -\paragraph_indentation default -\is_math_indent 0 -\math_numbering_side default -\quotes_style english -\dynamic_quotes 0 -\papercolumns 1 -\papersides 1 -\paperpagestyle default -\tablestyle default -\tracking_changes false -\output_changes false -\change_bars false -\postpone_fragile_content true -\html_math_output 0 -\html_css_as_file 0 -\html_be_strict false -\docbook_table_output 0 -\docbook_mathml_prefix 1 -\end_header - -\begin_body - -\begin_layout Section -Introduction -\begin_inset CommandInset label -LatexCommand label -name "sec:Introduction" - -\end_inset - - -\end_layout - -\begin_layout Standard -Neurodegenerative diseases are a serious threat to humans health. - One reason for these diseases is the swelling of axons, - caused by irregularities in intracellular traffic in the the axons. - Axons are a part of neurons, - transmitting an electrical signal. - These axons can be up to one meter in the human body and support little synthesis. - Therefore, - they need certain materials, - imported from the cytoplasm of the cell body. - -\end_layout - -\begin_layout Standard -\begin_inset Note Note -status open - -\begin_layout Itemize -Neurons -> highly specialized cells with long arms (processes). -\end_layout - -\begin_deeper -\begin_layout Itemize -axon: - if arm transmits electrical signal -\end_layout - -\begin_deeper -\begin_layout Itemize -up to one meter in human body -\end_layout - -\begin_layout Itemize -support little synthesis of proteins or membrane (transport equation needed) -\end_layout - -\begin_deeper -\begin_layout Itemize -materials must be constantly imported from synthetically active cytoplasm of cell body -\end_layout - -\begin_layout Itemize -Diffusion not fast enough (Einstein: - Brownian motion: - large molecules diffuse slower) -\end_layout - -\begin_deeper -\begin_layout Itemize -\begin_inset Quotes eld -\end_inset - -railway system -\begin_inset Quotes erd -\end_inset - -: - particles attach themselves to molecular motors to get transported to microtubules -\end_layout - -\begin_deeper -\begin_layout Itemize -molecular motor: - specialized protein that -\begin_inset Quotes eld -\end_inset - -walks -\begin_inset Quotes erd -\end_inset - - along intracellular filaments, - such as microtubules) -\end_layout - -\end_deeper -\end_deeper -\end_deeper -\end_deeper -\begin_layout Itemize -dendrite: - if arm receives electrical signal -\end_layout - -\begin_layout Itemize -Polarity: - All microtubules (MT) in axon have same polarity (plus ends point toward axon terminal) -\end_layout - -\begin_deeper -\begin_layout Itemize -kinesin-family molecular motors: - Transport towards plus-ends -\end_layout - -\begin_layout Itemize -dynein-family molecular motors: - Transport to minus-ends -\end_layout - -\begin_layout Itemize -\begin_inset Quotes eld -\end_inset - -Traffic jams -\begin_inset Quotes erd -\end_inset - -: -\end_layout - -\begin_deeper -\begin_layout Itemize -occur due to irregularities in intracellular traffic in axons -\end_layout - -\begin_deeper -\begin_layout Itemize -caused by mutations of molecular motors -> possible problems: - swelling of axons causing various neurodegenerative diseases -\end_layout - -\end_deeper -\end_deeper -\end_deeper -\begin_layout Itemize -Purpose of project: -\end_layout - -\begin_deeper -\begin_layout Itemize -Investige transport system from paper during molecular-motor-assisted transport of intracellular organelles utilizing transport equations -\end_layout - -\begin_deeper -\begin_layout Itemize -Learn about challenges when numerically solving advection equtaions -\end_layout - -\begin_layout Itemize -Understand transport behavior in axons -\end_layout - -\begin_layout Itemize -Identify possible dangers/problems -\end_layout - -\begin_layout Itemize -Why traffic jams occur? - Under which circumstances? -\end_layout - -\end_deeper -\end_deeper -\end_deeper -\end_inset - - -\end_layout - -\begin_layout Standard -Therefore, - the problem to be solved is a coupled system of partial differential equations, - consisting of one diffusion and two advection equations. - It reads: -\end_layout - -\begin_layout Standard -\begin_inset Formula -\begin{align} -\underbrace{\hat{n}_{\hat{t}}}_{\text{1.A}} & =\underbrace{\hat{D}_{0}\hat{n}_{\hat{x}\hat{x}}}_{\text{1.B}}-\underbrace{(1+\hat{k}_{-})\hat{n}+\hat{k}_{p}\hat{n}_{+}+\hat{k}_{n}\hat{n}_{-}}_{\text{1.C}}\label{eq:Dimensions_n}\\ -\underbrace{\left(\hat{n}_{+}\right)_{\hat{t}}}_{\text{2.A}}+\underbrace{\left(\frac{V_{+}}{V_{+,0}}\hat{n}_{+}\right)_{\hat{x}}}_{\text{2.B}} & =\underbrace{\hat{k_{+}}\hat{n}-\hat{k}_{p}\hat{n}_{+}}_{\text{2.C}}\qquad\hat{x}\in[0,\hat{L}]\label{eq:Dimensions_n+}\\ -\underbrace{\left(\hat{n}_{-}\right)_{\hat{t}}}_{\text{3.A}}+\underbrace{\left(\frac{V_{-}}{V_{+,0}}\hat{n}_{-}\right)_{\hat{x}}}_{\text{3.B}} & =\underbrace{\hat{k}_{-}\hat{n}-\hat{k}_{n}\hat{n}_{-}}_{\text{3.C}}\label{eq:Dimensions_n-} -\end{align} - -\end_inset - -with free particle concentration -\begin_inset Formula $\hat{n}$ -\end_inset - - and -\begin_inset Formula $\hat{n}_{\pm}$ -\end_inset - - the concentration of particles moving in positive/negative direction. - The spatial domain is described by -\begin_inset Formula $\Omega=[0,L]$ -\end_inset - - on a timeframe of -\begin_inset Formula $[0,t_{\text{end}}]$ -\end_inset - -. - Furthermore, - -\begin_inset Formula $\hat{D}_{0}$ -\end_inset - - is the diffusion coefficient, - -\begin_inset Formula $V_{\pm}$ -\end_inset - - the molecular motor velocity along microtubules regarding the -\begin_inset Formula $\pm$ -\end_inset - - direction, - -\begin_inset Formula $V_{\pm,0}$ -\end_inset - - molecular velocity along microtubules regarding -\begin_inset Formula $\pm$ -\end_inset - - direction in the case that the concentration of molecules riding on microtubules is very low, - the rate coefficients -\begin_inset Formula $\hat{k}_{p},\hat{k}_{n},\hat{k}_{+}$ -\end_inset - - and -\begin_inset Formula $\hat{k}_{-}$ -\end_inset - -. - Equation -\begin_inset CommandInset ref -LatexCommand ref -reference "eq:Dimensions_n" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - - describes the movement from the free particles by diffusion. - The temporal change is described by term 1.A and the diffusive behavior by 1.B. - The source term 1.C describes the exchange of particles with -\begin_inset Formula $\hat{n}_{\pm}$ -\end_inset - -. - The two advection equations -\begin_inset CommandInset ref -LatexCommand ref -reference "eq:Dimensions_n+" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - - and -\begin_inset CommandInset ref -LatexCommand ref -reference "eq:Dimensions_n-" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - - describe the movement of the particles moving in positive and negative direction due to convection. - The terms 2.A and 3.A describe the temporal change, - and 2.B and 3.B the advective behavior. - Both equations also have some exchange of concentration with the other particles, - described by terms 2.C and 3.C. -\end_layout - -\begin_layout Standard -Equations -\begin_inset CommandInset ref -LatexCommand ref -reference "eq:Dimensions_n+" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - - and -\begin_inset CommandInset ref -LatexCommand ref -reference "eq:Dimensions_n-" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - - can be reformulated into a generic advection equation of the form -\begin_inset Formula -\begin{equation} -u_{t}+a(x,t)u_{x}=q(x,t,u)\label{eq:GenericAdvectionEquation} -\end{equation} - -\end_inset - - with the advection velocity -\begin_inset Formula $a$ -\end_inset - -, - the property of interest -\begin_inset Formula $u$ -\end_inset - - and the source term -\begin_inset Formula $q$ -\end_inset - -. - This results in -\begin_inset Formula -\begin{align} -u_{t,2} & =\left(\hat{n}_{+}\right)_{\hat{t}},\quad a_{2}(x,t)=\frac{V_{+}}{V_{+,0}},\quad u_{x,2}=\hat{n}_{+,\hat{x}},\quad q_{3}(x,t,u)=\hat{k}_{p}\hat{n}-\hat{k}_{p}\hat{n}_{+}\\ -u_{t,3} & =\left(\hat{n}_{-}\right)_{\hat{t}},\quad a_{3}(x,t)=\frac{V_{-}}{V_{-,0}},\quad u_{x,3}=\hat{n}_{-,\hat{x}},\quad q_{3}(x,t,u)=\hat{k}_{-}\hat{n}-\hat{k}_{n}\hat{n}_{-} -\end{align} - -\end_inset - -Therefore, - it is sufficient to know how to deal with a generic advection equation in the form of equation -\begin_inset CommandInset ref -LatexCommand ref -reference "eq:GenericAdvectionEquation" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - - to solve the two advection equations, - describing the particle transport in axons, - both analytically and numerically. -\end_layout - -\begin_layout Standard -\begin_inset Note Note -status open - -\begin_layout Plain Layout -Engineering problem: -\end_layout - -\begin_layout Itemize -lets do some stuff -\end_layout - -\begin_layout Plain Layout -Mathematical model: -\end_layout - -\begin_layout Itemize -lets do some stuff -\end_layout - -\begin_layout Plain Layout -Purpose of each transport equation, - role of each term: -\end_layout - -\begin_layout Itemize -lets do some stuff -\end_layout - -\begin_layout Plain Layout -Few relevant research questions -\end_layout - -\begin_layout Itemize -lets do some stuff -\end_layout - -\begin_layout Plain Layout -Why need to know how to deal with generic advection equation? - ( -\begin_inset Formula $u_{t}+a(x,t)u_{x}=q(x,t,u)$ -\end_inset - - -\end_layout - -\begin_layout Itemize -lets do some stuff -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Standard -\begin_inset Float figure -placement document -alignment document -wide false -sideways false -status open - -\begin_layout Plain Layout - -\end_layout - -\begin_layout Plain Layout -\begin_inset Graphics - filename Figures/Schematic.jpg - width 30text% - -\end_inset - - -\begin_inset Caption Standard - -\begin_layout Plain Layout -\begin_inset CommandInset label -LatexCommand label -name "fig:Schematic" - -\end_inset - - -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Plain Layout - -\end_layout - -\end_inset - - -\end_layout - -\end_body -\end_document diff --git a/Project1/LyX/#Results.lyx# b/Project1/LyX/#Results.lyx# deleted file mode 100644 index 207080feeb363f36469905afb83adfa91cd09452..0000000000000000000000000000000000000000 --- a/Project1/LyX/#Results.lyx# +++ /dev/null @@ -1,1024 +0,0 @@ -#LyX 2.4 created this file. For more info see https://www.lyx.org/ -\lyxformat 620 -\begin_document -\begin_header -\save_transient_properties true -\origin unavailable -\textclass IEEEtran-CompSoc -\use_default_options true -\maintain_unincluded_children no -\language american -\language_package default -\inputencoding utf8 -\fontencoding auto -\font_roman "default" "default" -\font_sans "default" "default" -\font_typewriter "default" "default" -\font_math "auto" "auto" -\font_default_family default -\use_non_tex_fonts false -\font_sc false -\font_roman_osf false -\font_sans_osf false -\font_typewriter_osf false -\font_sf_scale 100 100 -\font_tt_scale 100 100 -\use_microtype false -\use_dash_ligatures true -\graphics default -\default_output_format default -\output_sync 0 -\bibtex_command default -\index_command default -\float_placement class -\float_alignment center -\paperfontsize default -\spacing single -\use_hyperref false -\papersize default -\use_geometry true -\use_package amsmath 1 -\use_package amssymb 1 -\use_package cancel 1 -\use_package esint 1 -\use_package mathdots 1 -\use_package mathtools 1 -\use_package mhchem 1 -\use_package stackrel 1 -\use_package stmaryrd 1 -\use_package undertilde 1 -\cite_engine basic -\cite_engine_type default -\biblio_style plain -\use_bibtopic false -\use_indices false -\paperorientation portrait -\suppress_date false -\justification true -\use_refstyle 1 -\use_formatted_ref 0 -\use_minted 0 -\use_lineno 0 -\index Index -\shortcut idx -\color #008000 -\end_index -\leftmargin 2.5cm -\topmargin 2.5cm -\rightmargin 2.5cm -\bottommargin 2.5cm -\secnumdepth 3 -\tocdepth 3 -\paragraph_separation indent -\paragraph_indentation default -\is_math_indent 0 -\math_numbering_side default -\quotes_style english -\dynamic_quotes 0 -\papercolumns 1 -\papersides 1 -\paperpagestyle default -\tablestyle default -\tracking_changes false -\output_changes false -\change_bars false -\postpone_fragile_content true -\html_math_output 0 -\html_css_as_file 0 -\html_be_strict false -\docbook_table_output 0 -\docbook_mathml_prefix 1 -\end_header - -\begin_body - -\begin_layout Section -Results -\begin_inset CommandInset label -LatexCommand label -name "sec:Results" - -\end_inset - - -\end_layout - -\begin_layout Standard -In the following the numerical approximations for the system will be discussed. - First, - the uncoupled system will be taken into account to then slowly increase the complexity, - ending in the fully coupled system with an additional hypothesis for the advective transport (see -\begin_inset CommandInset citation -LatexCommand cite -key "KUZNETSOV20085695" -literal "false" - -\end_inset - -). -\end_layout - -\begin_layout Subsection -Uncoupling the System -\begin_inset CommandInset label -LatexCommand label -name "subsec:Uncoupling-the-System" - -\end_inset - - -\end_layout - -\begin_layout Standard -Consider the uncoupled system of equations -\begin_inset Formula -\begin{align} -n_{t} & =D_{0}n_{xx}\\ -\left(n_{+}\right)_{t}+\left(n_{+}\right)_{x} & =0\label{eq:Results_uncoupled_n+}\\ -\left(n_{-}\right)-\left(n_{-}\right)_{x} & =0\label{eq:Results_uncoupled_n-} -\end{align} - -\end_inset - -with the analytical solutions for equations -\begin_inset CommandInset ref -LatexCommand ref -reference "eq:Results_uncoupled_n+" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - - and -\begin_inset CommandInset ref -LatexCommand ref -reference "eq:Results_uncoupled_n-" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - -, - as found in section -\begin_inset CommandInset ref -LatexCommand ref -reference "subsec:Method-of-Characteristics" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - -. - -\end_layout - -\begin_layout Standard -\begin_inset Float figure -placement document -alignment document -wide false -sideways false -status open - -\begin_layout Plain Layout -\begin_inset Graphics - filename Figures/Solution_Reduced_1D.pdf - width 100text% - -\end_inset - - -\begin_inset Caption Standard - -\begin_layout Plain Layout -The free particles already fulfill the diffusion equation at all times, - while the particles moving along one direction are propagated from the Dirichlet boundary towards the domain. - This propagation results in a shock at -\begin_inset Formula $x=t$ -\end_inset - -, - as the advection velocity has the value 1. - The x-axis shows the spatial domain while the y-axis shows the concentration for the free particles (left), - particles moving in positive direction (center) and particles moving in negative direction (right) at time -\begin_inset Formula $t=10$ -\end_inset - -. - The initial values are visualized with dotted lines, - the numerical with solid lines and the analytical with dashed lines. -\begin_inset CommandInset label -LatexCommand label -name "fig:Uncoupled_1D_t=10" - -\end_inset - - -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Plain Layout - -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Standard -Figure -\begin_inset CommandInset ref -LatexCommand ref -reference "fig:Uncoupled_1D_t=10" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - - visualizes the state of the different concentrations after a time of -\begin_inset Formula $t=10$ -\end_inset - - dimensionless units. - The free particle concentration ( -\begin_inset Formula $n$ -\end_inset - -) is the same as initially, - as this already fulfills the Diffusion equation. - The concentrations of particles moving in positive ( -\begin_inset Formula $n_{+}$ -\end_inset - -) and negative ( -\begin_inset Formula $n_{-}$ -\end_inset - -) direction are propagated, - starting at the Dirichlet boundary, - with an advection speed of 1. - Therefore, - the analytical solution shows a shocks at the -\begin_inset Formula $x=t$ -\end_inset - - from the Dirichlet boundary value to the initial value zero. - The finite difference scheme is not capable to capture this discontinuity, - as it is only a method of first order discretized in time with an explicit Euler. - Therefore, - the numerical solution shows some error close to the shock. -\end_layout - -\begin_layout Standard -As the concentration is propagated with a propagation speed of -\begin_inset Formula $1$ -\end_inset - - over a domain of length -\begin_inset Formula $20$ -\end_inset - -, - it takes 20 dimensionless time units to fully propagate from one boundary to the other. - This justifies the time choice of 10 dimensionless units from before. -\end_layout - -\begin_layout Standard -\begin_inset Float figure -placement document -alignment document -wide false -sideways false -status open - -\begin_layout Plain Layout - -\end_layout - -\begin_layout Plain Layout -\begin_inset Box Frameless -position "t" -hor_pos "c" -has_inner_box 1 -inner_pos "t" -use_parbox 0 -use_makebox 0 -width "75text%" -special "none" -height "1in" -height_special "totalheight" -thickness "0.4pt" -separation "3pt" -shadowsize "4pt" -framecolor "foreground" -backgroundcolor "none" -status open - -\begin_layout Plain Layout -\begin_inset Float figure -placement document -alignment document -wide false -sideways false -status open - -\begin_layout Plain Layout - -\end_layout - -\begin_layout Plain Layout -\begin_inset Graphics - filename Figures/Solution_Reduced_3D_Propagation.pdf - width 100text% - -\end_inset - - -\begin_inset Caption Standard - -\begin_layout Plain Layout -Propagation -\begin_inset CommandInset label -LatexCommand label -name "fig:PropagationTime" - -\end_inset - - -\end_layout - -\end_inset - - -\end_layout - -\end_inset - - -\end_layout - -\end_inset - - -\begin_inset Newline newline -\end_inset - - -\begin_inset Box Frameless -position "t" -hor_pos "c" -has_inner_box 1 -inner_pos "t" -use_parbox 0 -use_makebox 0 -width "50text%" -special "none" -height "1in" -height_special "totalheight" -thickness "0.4pt" -separation "3pt" -shadowsize "4pt" -framecolor "foreground" -backgroundcolor "none" -status open - -\begin_layout Plain Layout -\begin_inset Float figure -placement document -alignment document -wide false -sideways false -status open - -\begin_layout Plain Layout - -\end_layout - -\begin_layout Plain Layout -\begin_inset Graphics - filename Figures/Flux_Reduced_1D_Propagation.pdf - lyxscale 50 - width 100text% - -\end_inset - - -\begin_inset Caption Standard - -\begin_layout Plain Layout -Flux -\begin_inset CommandInset label -LatexCommand label -name "fig:PropagationTime_Flux" - -\end_inset - - -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Plain Layout - -\end_layout - -\end_inset - - -\end_layout - -\end_inset - - -\begin_inset Caption Standard - -\begin_layout Plain Layout -Propagation of concentration and flux -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Plain Layout - -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Standard -Figure -\begin_inset CommandInset ref -LatexCommand ref -reference "fig:PropagationTime" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - - shows the three different concentrations for -\begin_inset Formula $t\in[0,25]$ -\end_inset - -, - calculated numerically. - The numerical solution needs longer to be fully propagated, - due to the numerical error. - However, - after -\begin_inset Formula $21.85$ -\end_inset - - time units, - also the numerical solution is fully propagated, - resulting in the stationary solution for -\begin_inset Formula $t>21.85$ -\end_inset - -. - -\end_layout - -\begin_layout Standard -Summing up equations -\begin_inset CommandInset ref -LatexCommand ref -reference "eq:Dimensionless_n" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - -- -\begin_inset CommandInset ref -LatexCommand ref -reference "eq:Dimensionless_n_-" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - - results in -\begin_inset Formula -\begin{align} -(n+n_{+}+n_{-})_{t}+(\underbrace{n_{+}-n_{-}-D_{0}n_{x}}_{J})_{x} & =0 -\end{align} - -\end_inset - -Where -\begin_inset Formula $n_{+}-n_{-}-D_{0}n_{x}$ -\end_inset - - is the total flux -\begin_inset Formula $J$ -\end_inset - -. - This total flux should will vary initially and result in a constant solution after the different concentrations reached the stationary behavior. - The total mass will reach its stationary solution at the same time as the total flux, - namely -\begin_inset Formula $t=20$ -\end_inset - - analytically and -\begin_inset Formula $t=21.85$ -\end_inset - - numerically. - -\end_layout - -\begin_layout Subsection -Increasing the Complexity by Adding Source Terms -\begin_inset CommandInset label -LatexCommand label -name "subsec:Increasing-the-Complexity" - -\end_inset - - -\end_layout - -\begin_layout Standard -As a next step, - the source terms will be partly integrated into the system. - First consider the uncoupled system with source terms connecting the free particles, - resulting in -\begin_inset Formula -\begin{align} -n_{t} & =D_{0}n_{xx}-(1+k_{-})n\label{eq:Results_uncoupled_n_Source_n}\\ -\left(n_{+}\right)_{t}+\left(n_{+}\right)_{x} & =n\label{eq:Results_uncoupled_n+_Source_n}\\ -\left(n_{-}\right)-\left(n_{-}\right)_{x} & =k_{-}n\label{eq:Results_uncoupled_n-_Source_n} -\end{align} - -\end_inset - - -\end_layout - -\begin_layout Standard -The term -\begin_inset Formula $-(1+k_{-})n$ -\end_inset - - in equation -\begin_inset CommandInset ref -LatexCommand ref -reference "eq:Results_uncoupled_n_Source_n" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - - models the loss in particles from free particles towards particles moving along one direction. - As these particles are added towards the moving particles along a traction, - they are also added to the right-hand-side of equation -\begin_inset CommandInset ref -LatexCommand ref -reference "eq:Results_uncoupled_n+_Source_n" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - - ( -\begin_inset Formula $n$ -\end_inset - -) and equation -\begin_inset CommandInset ref -LatexCommand ref -reference "eq:Results_uncoupled_n-_Source_n" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - - ( -\begin_inset Formula $k_{-}n$ -\end_inset - -). -\end_layout - -\begin_layout Standard -\begin_inset Float figure -placement document -alignment document -wide false -sideways false -status open - -\begin_layout Plain Layout -\begin_inset Float figure -placement document -alignment document -wide false -sideways false -status open - -\begin_layout Plain Layout -\begin_inset Graphics - filename Figures/Solution_Reduced_1D_SourceTerms.pdf - width 100text% - -\end_inset - - -\end_layout - -\begin_layout Plain Layout -\begin_inset Caption Standard - -\begin_layout Plain Layout -\begin_inset Formula $t=10$ -\end_inset - - -\end_layout - -\end_inset - - -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Plain Layout -\begin_inset Float figure -placement document -alignment document -wide false -sideways false -status open - -\begin_layout Plain Layout - -\end_layout - -\begin_layout Plain Layout -\begin_inset Graphics - filename Figures/Solution_Reduced_3D_SourceTerms_contourf.pdf - width 100text% - -\end_inset - - -\begin_inset Caption Standard - -\begin_layout Plain Layout - -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Plain Layout - -\end_layout - -\end_inset - - -\begin_inset Caption Standard - -\begin_layout Plain Layout -Source Terms -\begin_inset CommandInset label -LatexCommand label -name "fig:AddingSourceWithn" - -\end_inset - - -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Plain Layout - -\end_layout - -\end_inset - -Figure -\begin_inset CommandInset ref -LatexCommand ref -reference "fig:AddingSourceWithn" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - - visualizes the concentrations (y-axis) over the spatial domain (x-axis) for the three different concentrations, - according to this simple coupling at time -\begin_inset Formula $t=10$ -\end_inset - -. - -\end_layout - -\begin_layout Standard -The free particles concentration starts to change over time, - as it loses particles to the other particle types. - In the center of the domain, - there are no free particles anymore and close to the boundaries, - the free particle concentration increases towards their Dirichlet values. - -\end_layout - -\begin_layout Standard -\begin_inset Float figure -placement document -alignment document -wide false -sideways false -status open - -\begin_layout Plain Layout -\begin_inset Float figure -placement document -alignment document -wide false -sideways false -status open - -\begin_layout Plain Layout -\begin_inset Graphics - filename Figures/Solution_Reduced_1D_ReactionTerms.pdf - width 100text% - -\end_inset - - -\end_layout - -\begin_layout Plain Layout -\begin_inset Caption Standard - -\begin_layout Plain Layout -\begin_inset Formula $t=10$ -\end_inset - - -\end_layout - -\end_inset - - -\end_layout - -\end_inset - - -\begin_inset Float figure -placement document -alignment document -wide false -sideways false -status open - -\begin_layout Plain Layout - -\end_layout - -\begin_layout Plain Layout -\begin_inset Graphics - filename Figures/Solution_Reduced_3D_ReactionTerms_contourf.pdf - width 100text% - -\end_inset - - -\begin_inset Caption Standard - -\begin_layout Plain Layout - -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Plain Layout - -\end_layout - -\end_inset - - -\begin_inset Caption Standard - -\begin_layout Plain Layout -Reaction Terms -\end_layout - -\end_inset - - -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Standard -\begin_inset Float figure -placement document -alignment document -wide false -sideways false -status open - -\begin_layout Plain Layout -\begin_inset Float figure -placement document -alignment document -wide false -sideways false -status open - -\begin_layout Plain Layout -\begin_inset Graphics - filename Figures/Solution_Reduced_1D_FullTerms.pdf - width 100text% - -\end_inset - - -\end_layout - -\begin_layout Plain Layout -\begin_inset Caption Standard - -\begin_layout Plain Layout -\begin_inset Formula $t=10$ -\end_inset - - -\end_layout - -\end_inset - - -\end_layout - -\end_inset - - -\begin_inset Float figure -placement document -alignment document -wide false -sideways false -status open - -\begin_layout Plain Layout - -\end_layout - -\begin_layout Plain Layout -\begin_inset Graphics - filename Figures/Solution_Reduced_3D_FullTerms_contourf.pdf - width 100text% - -\end_inset - - -\begin_inset Caption Standard - -\begin_layout Plain Layout - -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Plain Layout - -\end_layout - -\end_inset - - -\begin_inset Caption Standard - -\begin_layout Plain Layout -Source Terms -\end_layout - -\end_inset - - -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Subsection -Nonlinear Velocity Profile -\begin_inset CommandInset label -LatexCommand label -name "subsec:Nonlinear-Velocity-Profile" - -\end_inset - - -\end_layout - -\begin_layout Standard -\begin_inset Float figure -placement document -alignment document -wide false -sideways false -status open - -\begin_layout Plain Layout - -\end_layout - -\begin_layout Plain Layout -\begin_inset Graphics - filename Figures/Solution_Full_1D_Exponential.pdf - width 100text% - -\end_inset - - -\begin_inset Caption Standard - -\begin_layout Plain Layout -Nonlinear advection equation -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Plain Layout - -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Standard - -\end_layout - -\end_body -\end_document diff --git a/Project1/LyX/#TheoryAndMethods.lyx# b/Project1/LyX/#TheoryAndMethods.lyx# deleted file mode 100644 index 29d679d642b2a06dda9e939c0ac7be095baaa019..0000000000000000000000000000000000000000 --- a/Project1/LyX/#TheoryAndMethods.lyx# +++ /dev/null @@ -1,608 +0,0 @@ -#LyX 2.4 created this file. For more info see https://www.lyx.org/ -\lyxformat 620 -\begin_document -\begin_header -\save_transient_properties true -\origin unavailable -\textclass IEEEtran-CompSoc -\use_default_options true -\maintain_unincluded_children no -\language american -\language_package default -\inputencoding utf8 -\fontencoding auto -\font_roman "default" "default" -\font_sans "default" "default" -\font_typewriter "default" "default" -\font_math "auto" "auto" -\font_default_family default -\use_non_tex_fonts false -\font_sc false -\font_roman_osf false -\font_sans_osf false -\font_typewriter_osf false -\font_sf_scale 100 100 -\font_tt_scale 100 100 -\use_microtype false -\use_dash_ligatures true -\graphics default -\default_output_format default -\output_sync 0 -\bibtex_command default -\index_command default -\float_placement class -\float_alignment center -\paperfontsize default -\spacing single -\use_hyperref false -\papersize default -\use_geometry true -\use_package amsmath 1 -\use_package amssymb 1 -\use_package cancel 1 -\use_package esint 1 -\use_package mathdots 1 -\use_package mathtools 1 -\use_package mhchem 1 -\use_package stackrel 1 -\use_package stmaryrd 1 -\use_package undertilde 1 -\cite_engine basic -\cite_engine_type default -\biblio_style plain -\use_bibtopic false -\use_indices false -\paperorientation portrait -\suppress_date false -\justification true -\use_refstyle 1 -\use_formatted_ref 0 -\use_minted 0 -\use_lineno 0 -\index Index -\shortcut idx -\color #008000 -\end_index -\spellchecker_ignore american Sobolev -\spellchecker_ignore american OpenMP -\spellchecker_ignore american scalable -\spellchecker_ignore american discretized -\spellchecker_ignore american splitted -\spellchecker_ignore american bilinear -\leftmargin 2.5cm -\topmargin 2.5cm -\rightmargin 2.5cm -\bottommargin 2.5cm -\secnumdepth 3 -\tocdepth 3 -\paragraph_separation indent -\paragraph_indentation default -\is_math_indent 0 -\math_numbering_side default -\quotes_style english -\dynamic_quotes 0 -\papercolumns 1 -\papersides 1 -\paperpagestyle default -\tablestyle default -\tracking_changes false -\output_changes false -\change_bars false -\postpone_fragile_content true -\html_math_output 0 -\html_css_as_file 0 -\html_be_strict false -\docbook_table_output 0 -\docbook_mathml_prefix 1 -\end_header - -\begin_body - -\begin_layout Section -Theory and Methods -\begin_inset CommandInset label -LatexCommand label -name "sec:Theory-and-Methods" - -\end_inset - - -\end_layout - -\begin_layout Subsection -Dimensionless Properties -\end_layout - -\begin_layout Standard -Dimensionless quantities are introduced in the following to scale the physical values to some reference level. - The dimensionless quantities are defined as follows (compare with -\begin_inset CommandInset citation -LatexCommand cite -key "KUZNETSOV20085695" -literal "false" - -\end_inset - -) -\end_layout - -\begin_layout Standard -\begin_inset Formula -\begin{align*} -\hat{x} & =\frac{xk_{+}}{V_{+,0}},\hphantom{\hat{k}\frac{k_{-}}{k_{+}}}\hat{t}=tk_{+},\hphantom{\hat{k}_{p}\frac{k_{p}}{k_{+}}}\hat{D}_{0}=\frac{D_{0}k_{p}}{V_{+,0}^{2}},\hphantom{\hat{k}_{n}\frac{k_{n}}{k_{+}}}\hat{n}=\frac{nV_{+,0}^{3}}{k_{+}^{3}},\quad\hat{n_{\pm}=\frac{n_{\pm}V_{+,0}^{3}}{k_{\pm}^{3}}}\\ -\hat{k}_{-} & =\frac{k_{-}}{k_{+}},\hphantom{\hat{x}\frac{xk_{+}}{V_{+,0}}}\hat{k}_{p}=\frac{k_{p}}{k_{+}},\hphantom{\hat{t}tk_{+}}\hat{k}_{n}=\frac{k_{n}}{k_{+}},\hphantom{\hat{D}_{0}\frac{D_{0}k_{p}}{V_{+,0}^{2}}}\hat{V}_{-,0}=\frac{V_{-,0}}{V_{+,0}} -\end{align*} - -\end_inset - -Inserting the dimensionless quantities in equations -\begin_inset CommandInset ref -LatexCommand ref -reference "eq:Dimensions_n" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - -, - -\begin_inset CommandInset ref -LatexCommand ref -reference "eq:Dimensions_n+" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - - and -\begin_inset CommandInset ref -LatexCommand ref -reference "eq:Dimensions_n-" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - - under the additional assumption of constant velocities ( -\begin_inset Formula $V_{+}=V_{+,0},V_{-}=V_{-,0}=-V_{+,0})$ -\end_inset - -, - yields the dimensionless system of equations -\begin_inset Formula -\begin{align} -n_{t} & =D_{0}n_{xx}-\left(1+k_{-}\right)n+k_{p}n_{+}+k_{n}n_{-}\label{eq:Dimensionless_n}\\ -\left(n_{+}\right)_{t}+\left(n_{+}\right)_{x} & =k_{+}n-k_{p}n_{+}\qquad x\in[0,L]\label{eq:Dimensionless_n_+}\\ -\left(n_{-}\right)_{t}-\left(n_{-}\right)_{x} & =k_{-}n-k_{n}n_{-}\label{eq:Dimensionless_n_-} -\end{align} - -\end_inset - - -\end_layout - -\begin_layout Subsection -Initial- and Boundary Conditions -\end_layout - -\begin_layout Standard -For the initial state a linear relation for the free particles and a vanishing amount of particles moving along one direction is used -\begin_inset Formula -\begin{align} -n(x,t=0) & =n^{0}(x)=+\left(N_{L}-N_{0}\right)\frac{x}{L}\\ -n_{+}(x,t=0) & =n_{+}^{0}(x)=0\\ -n_{-}(x,t=0) & =n_{-}^{0}(x)=0 -\end{align} - -\end_inset - - -\end_layout - -\begin_layout Subsection -Different Hypothesis's for Advective Transport -\end_layout - -\begin_layout Standard -\begin_inset Note Note -status open - -\begin_layout Plain Layout -To Do -\end_layout - -\end_inset - - -\end_layout - -\begin_layout Subsection -Method of Characteristics -\begin_inset CommandInset label -LatexCommand label -name "subsec:Method-of-Characteristics" - -\end_inset - - -\end_layout - -\begin_layout Standard -The method of characteristics (MOC) can be utilized to solve an advection equation in terms of an initial-value problem. - Uncoupling equation -\begin_inset CommandInset ref -LatexCommand ref -reference "eq:Dimensionless_n_+" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - - from the remaining equations results in -\begin_inset Formula -\begin{align} -\left(n_{+}\right)_{t}+\left(n_{+}\right)_{x} & =0\\ -\Leftrightarrow U_{t}+U_{x} & =0\label{eq:Characteristic_UtUx}\\ -\text{with: }U(x,0) & =U_{0}(x)\quad\forall x\in\mathbb{R} -\end{align} - -\end_inset - -As an ansatz assume that some curve -\begin_inset Formula $x(t)$ -\end_inset - - along the slope of -\begin_inset Formula $U$ -\end_inset - - is constant, - meaning -\begin_inset Formula -\begin{align} -0 & =\frac{d}{dt}U\left(x(t),t\right)\\ - & =U_{t}\left((x(t),t\right)+U_{x}\left(x(t),t\right)\frac{dx}{dt} -\end{align} - -\end_inset - -As -\begin_inset Formula $U_{t}+U_{x}=0$ -\end_inset - - (see equation -\begin_inset CommandInset ref -LatexCommand ref -reference "eq:Characteristic_UtUx" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - -) -\begin_inset Formula $\frac{dx}{dt}$ -\end_inset - - has to be equal to one to fulfill the partial differential equation. - Insert this with -\begin_inset Formula -\begin{align} -\frac{dx}{dt} & =1\quad\text{with: }x(0)=x_{0}\\ -\Rightarrow x(t) & =x_{0}+t -\end{align} - -\end_inset - -resulting in the solution -\begin_inset Formula $U(x,t)=U_{0}(x_{0})=U_{0}(x-t)$ -\end_inset - - and for the concentrations -\begin_inset Formula -\begin{equation} -n_{+}(x,t)=n_{+,0}(x-t) -\end{equation} - -\end_inset - -The analytical solution for the uncoupled equation -\begin_inset CommandInset ref -LatexCommand ref -reference "eq:Dimensionless_n_-" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - - can be derived in the same way, - resulting in -\begin_inset Formula $n_{-}(x,t)=n_{-,0}(x+t)$ -\end_inset - -. - Note that the advection velocity is now -\begin_inset Formula $a=-1$ -\end_inset - -, - therefore -\begin_inset Formula $\frac{dx}{dt}=-1$ -\end_inset - - has to be fulfilled. - -\end_layout - -\begin_layout Subsection -Discretization with Finite Differences and Upwind Discretization -\end_layout - -\begin_layout Standard -The coupled system of equations will be solved numerically with the finite-difference scheme and an upwind-discretization for the advective term. - In the discrete terms, - the upper index -\begin_inset Formula $\cdot^{j}$ -\end_inset - - indicates the -\begin_inset Formula $j$ -\end_inset - --th time step, - while the lower index -\begin_inset Formula $\cdot_{i}$ -\end_inset - - indicates the i-th grid point. - -\begin_inset Formula $\Delta t$ -\end_inset - - is the time-step size and -\begin_inset Formula $\Delta x$ -\end_inset - - the distant between two grid points on an uniform grid. -\end_layout - -\begin_layout Standard -Discretizing the time with a simple explicit Euler method, - the diffusion coefficient with a finite difference stencil of second order and the advective terms with an Upwind discretization, - the discretized equations are as follows -\begin_inset Formula -\begin{align} -\frac{n_{i}^{j+1}-n_{i}^{j}}{\Delta t} & =D_{0}\frac{n_{i+1}^{j}-2n_{i}^{j}+n_{i-1}^{j}}{(\Delta x)^{2}}-(1+k_{-})n_{i}^{j}+k_{p}n_{+,i}^{j}+k_{n}n_{-,i}^{j}\label{eq:Discretized_1}\\ -\frac{n_{+,i}^{j+1}-n_{+,i}^{j}}{\Delta t}+\frac{1}{\Delta x}\left(U_{+,i+\frac{1}{2}}^{j}-U_{+,i-\frac{1}{2}}^{j}\right) & =k_{-}n_{i}^{j}-k_{p}n_{+,i}^{j}\label{eq:Discretized_2}\\ -\frac{n_{-,i}^{j+1}-n_{-,i}^{j}}{\Delta t}-\frac{1}{\Delta x}\left(U_{-,i+\frac{1}{2}}^{j}-U_{-,i-\frac{1}{2}}^{j}\right) & =k_{-}n_{i}^{j}-k_{n}n_{-,i}^{j}\label{eq:Discretized_3} -\end{align} - -\end_inset - -with -\begin_inset Note Note -status open - -\begin_layout Plain Layout -Check this -\end_layout - -\end_inset - - -\begin_inset Formula -\begin{align} -U_{+,i+\frac{1}{2}}^{j} & =n_{+,i}^{j},\quad U_{+,i-\frac{1}{2}}^{j}=n_{+,i-1}^{j}\label{eq:Upwind_+}\\ -U_{-,i+\frac{1}{2}}^{j} & =n_{-,i+1}^{j},\quad U_{-,i-\frac{1}{2}}^{j}=n_{-,i}^{j}\label{eq:Upwind_-} -\end{align} - -\end_inset - -Inserting the upwind formulations into the discretized system of equations ( -\begin_inset CommandInset ref -LatexCommand ref -reference "eq:Discretized_1" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - -- -\begin_inset CommandInset ref -LatexCommand ref -reference "eq:Discretized_3" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - -) and reformulating this yields an explicit scheme for time-step -\begin_inset Formula $j+1$ -\end_inset - -, - depending on time-step -\begin_inset Formula $j$ -\end_inset - -. -\begin_inset Formula -\begin{align} -n_{i}^{j+1} & =n_{i}^{j}+\Delta t\left(D_{0}\frac{n_{i+1}^{j}-2n_{i}^{j}+n_{i-1}^{j}}{(\Delta x)^{2}}-(1+k_{-})n_{i}^{j}+k_{p}n_{+,i}^{j}+k_{n}n_{-,i}^{j}\right)\label{eq:Discretized_Explicit_1}\\ -n_{+,i}^{j+1} & =n_{-,i}^{j}+\Delta t\left(-\frac{1}{\Delta x}\left(n_{+,i}^{j}-n_{+,i-1}^{j}\right)+k_{-}n_{i}^{j}-k_{p}n_{+,i}^{j}\right)\\ -n_{-,i}^{j+1} & =n_{-,i}^{j}+\Delta t\left(+\frac{1}{\Delta x}\left(n_{-,i+1}^{j}-n_{-,i}^{j}\right)+k_{-}n_{i}^{j}-k_{n}n_{-,i}^{j}\right)\label{eq:Discretized_Explicit_3} -\end{align} - -\end_inset - -which is straight forward to implement in Python with the numpy library, - in the case of homogeneous Neumann boundary conditions, - as they will be used in this work. - A for-loop over all time steps has to be implemented and for each time-step the explicit update, - following equations -\begin_inset CommandInset ref -LatexCommand ref -reference "eq:Discretized_Explicit_1" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - -- -\begin_inset CommandInset ref -LatexCommand ref -reference "eq:Discretized_Explicit_3" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - -, - has to be called. - After this, - the Dirichlet boundary conditions can be enforced by setting the boundary points -\begin_inset Formula $n_{0}^{j+1},n_{m}^{j+1},n_{+,0}^{j+1},n_{-,m}^{j+1}$ -\end_inset - - to their respective value. -\end_layout - -\begin_layout Subsection -Stability -\end_layout - -\begin_layout Standard -As the numerical scheme is of an explicit form, - it is not unconditionally stable. - For the -\begin_inset Formula $L^{1}$ -\end_inset - --estimate, - to fulfill conservation of the concentrations -\begin_inset Formula $n,n_{+},n_{-}$ -\end_inset - -, - the scheme has to fulfill -\begin_inset Formula -\begin{equation} -\int_{0}^{1}|u(x,t)|dx\leq\int_{0}^{1}|u_{0}(x)|dx -\end{equation} - -\end_inset - -or in the discretized formulation -\begin_inset Formula -\begin{equation} -\sum_{j=1}^{M}|u_{j}^{n+1}|\Delta x\leq\sum_{j=1}^{M}|u_{0,j}|\Delta x\quad\Leftrightarrow\sum_{j=1}^{M}|u_{j}^{n+1}|\leq\sum_{j=1}^{n}|u_{j}^{n}|\label{eq:Stability_Constraint} -\end{equation} - -\end_inset - -For the two uncoupled advection equations under the assumptions of a uniform advection velocity -\begin_inset Formula $a$ -\end_inset - -=1 this results in the following derivation. - -\end_layout - -\begin_layout Standard -With the triangular inequality ( -\begin_inset Formula $|a+b|\leq|a|+|b|$ -\end_inset - -) and -\begin_inset Formula $\lambda=\frac{\Delta t}{\Delta x}$ -\end_inset - - the concentration at the next time step can be reformulated to -\begin_inset Formula -\begin{equation} -\left|u_{j}^{n+1}\right|u_{j}^{n}-\lambda(u_{j}^{n}-u_{j-1}^{n})\leq(1-\lambda)\left|u_{j}^{n}\right|+\lambda\left|u_{j-1}^{n}\right| -\end{equation} - -\end_inset - -under the constraint -\begin_inset Formula $1-\lambda\geq0$ -\end_inset - -. - Tis discretized concentration can be inserted into equation -\begin_inset CommandInset ref -LatexCommand ref -reference "eq:Stability_Constraint" -plural "false" -caps "false" -noprefix "false" -nolink "false" - -\end_inset - - to get -\begin_inset Formula -\begin{align} -\sum_{j=1}^{M}\left|u_{j}^{n+1}\right| & \leq(1-\lambda)\sum_{j=1}^{M}\left|u_{j}^{n}\right|+\lambda\sum_{j=1}^{M}\left|u_{j-1}^{n}\right|\\ - & =(1-\lambda)\sum_{j=1}^{M}\left|u_{j}^{n}\right|+\lambda\sum_{j=1}^{M}\left|u_{j}^{n}\right|\\ - & =\sum_{j=1}^{M}\left|u_{j}^{n}\right| -\end{align} - -\end_inset - -Therefore, - the discretization for the advection equation is stable under the condition -\begin_inset Formula -\begin{align} -1-\lambda & =1-\frac{\Delta t}{\Delta x}\geq0\\ -\Leftrightarrow\frac{\Delta t}{\Delta x} & \leq1 -\end{align} - -\end_inset - -For general advection equation ( -\begin_inset Formula $a=a)$ -\end_inset - - the stability constraint is called the CFL-condition and reads: -\begin_inset Formula -\begin{equation} -a\frac{\Delta t}{\Delta x}\leq1 -\end{equation} - -\end_inset - -For the diffusion equation a similar derivation stability can be performed, - resulting in the more strict constraint -\begin_inset Formula -\begin{equation} -D_{0}\frac{\Delta t}{\left(\Delta x\right)^{2}}\leq\frac{1}{2} -\end{equation} - -\end_inset - - -\end_layout - -\end_body -\end_document