Finite difference method nonlinear PDE

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SUMMARY

The discussion focuses on solving nonlinear partial differential equations (PDEs) using the finite difference method (FDM). It emphasizes that a straightforward discretization approach, effective for linear PDEs, is inadequate for nonlinear PDEs due to their complexity. The user presents specific nonlinear equations and boundary conditions, seeking guidance on the correct application of FDM and relevant resources for further study. The consensus is that nonlinear PDEs require tailored methods beyond basic discretization techniques.

PREREQUISITES
  • Understanding of nonlinear partial differential equations (PDEs)
  • Familiarity with finite difference method (FDM) for numerical analysis
  • Knowledge of boundary value problems and their conditions
  • Proficiency in mathematical modeling and discretization techniques
NEXT STEPS
  • Study advanced finite difference methods for nonlinear PDEs
  • Explore numerical stability and convergence criteria in FDM
  • Research specific techniques like the method of lines for nonlinear PDEs
  • Review literature on numerical solutions for nonlinear systems, such as "Numerical Methods for Partial Differential Equations" by J. W. Thomas
USEFUL FOR

Mathematicians, engineers, and researchers involved in computational fluid dynamics, structural analysis, and anyone tackling nonlinear PDEs using numerical methods.

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i want to solve a nonlinear PDE with finite difference method ,but using just discretization like in linear PDE , it will lead to nowhere , what's the right way to use FDM to solve nonlinear PDE or could someone provide me with book's titles or articles that can help me solving a nonlinear pdf using FDM
 
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Last-cloud said:
i want to solve a nonlinear PDE with finite difference method ,but using just discretization like in linear PDE , it will lead to nowhere , what's the right way to use FDM to solve nonlinear PDE or could someone provide me with book's titles or articles that can help me solving a nonlinear pdf using FDM

There is no single finite difference discretization that works well for all problems. This is true for both linear and nonlinear PDEs. Most methods used to solve nonlinear systems are based off of methods that work for linear models of the nonlinear problem. And I'm not sure what you mean by we you say "discretization like a linear PDE, it will lead to nowhere." It is true that nonlinear PDE's can be substantially more difficult to analyze, and there are additional issues that can arise.

Do you have a particular problem in mind? Are you running into a specific issue?
 
yes , i have a problem ;
\begin{equation}
m_{z}\ddot{w}+EIw'''-Tw''-f+c_{1}\dot{w}-EAv''w'-EAv'w''-\dfrac{3}{2}EA(w')^2w''=0
\end{equation}
\begin{equation}
m_{z}\ddot{v}+c_{2}\dot{v}-EAv''-EAw'w''=0
\end{equation}
the boundary conditions of the system :
\begin{equation}
w''(0,t)=w''(L,t)=w(0,t)=v(0,t)=0
\end{equation}
\begin{equation}
-EIw'''(L,t)+Tw'(L,t)+EAv'(L,t)w'(L,t)+\dfrac{1}{2}EA\left[ w'(L,t)\right] ^{3}=u_{T}(t)
\end{equation}
\begin{equation}
\dfrac{1}{2}EA[w'(L,t)]^{2}+EAv'(L,t)=u_{L}(t)
\end{equation}
\begin{equation}
w(x,0)=w'(x,0)=v(x,0)=v'(x,0)=0
\end{equation}
where
\begin{equation}
w'=\dfrac{\partial w(x,t)}{\partial x} \;\; and \;\; \dot{w}=\dfrac{\partial w(x,t)}{\partial t}
\end{equation}
what I've tried to do is:
\begin{equation}
\begin{split}
& m_{z}\left( \dfrac{w_{i}^{j+1}-2w_{i}^{j}+w_{i}^{j-1}}{k^{2}}\right)+ EI\left( \dfrac{w_{i+2}^{j}-2w_{i+1}^{j}+2w_{i-1}^{j}-w_{i-2}^{j}}{2h^{3}}\right)-T\left( \dfrac{w_{i+1}^{j}-2w_{i}^{j}+w_{i-1}^{j}}{h^{2}}\right)+c_{1}\left( \dfrac{w_{i}^{j+1}-w_{i}^{j}}{k}\right)-\\
& EA\left( \dfrac{v_{i+1}^{j}-2v_{i}^{j}+v_{i-1}^{j}}{h^{2}}\right)\left( \dfrac{w_{i+1}^{j}-w_{i}^{j}}{h}\right)-EA \left( \dfrac{v_{i+1}^{j}-v_{i}^{j}}{h}\right)\left( \dfrac{w_{i+1}^{j}-2w_{i}^{j}+w_{i-1}^{j}}{h^{2}}\right)-\\
& \dfrac{3}{2}EA\left( \dfrac{w_{i+1}^{j}-w_{i}^{j}}{h}\right)^{2} \left( \dfrac{w_{i+1}^{j}-2w_{i}^{j}+w_{i-1}^{j}}{h^{2}}\right)=f
\end{split}
\end{equation}
and
\begin{equation}
\begin{split}
& m_{z}\left( \dfrac{v_{i}^{j+1}-2v_{i}^{j}+v_{i}^{j-1}}{k^{2}}\right)+c_{2}\left( \dfrac{v_{i}^{j+1}-v_{i}^{j}}{k}\right)- EA\left( \dfrac{v_{i+1}^{j}-2v_{i}^{j}+v_{i-1}^{j}}{h^{2}}\right)-\\
& EA\left( \dfrac{w_{i+1}^{j}-w_{i}^{j}}{h}\right) \left( \dfrac{w_{i+1}^{j}-2w_{i}^{j}+w_{i-1}^{j}}{h^{2}}\right)=0
\end{split}
\end{equation}
thus
the 1st equation of the system:
\begin{equation}
\begin{split}
&\left(\dfrac{(m_{z}+kc_{1})w_{i}^{j+1}-(2+kc_{1})w_{i}^{j}+w_{i}^{j-1}}{k^{2}}\right)+ \left( \dfrac{EIw_{i+2}^{j}-2(EI+Th)w_{i+1}^{j}+4Thw_{i}^{j}+2(EI-Th)w_{i-1}^{j}-EIw_{i-2}^{j}}{2h^{3}}\right)-\\
& EA\left( \dfrac{v_{i+1}^{j}-2v_{i}^{j}+v_{i-1}^{j}}{h^{2}}\right)\left( \dfrac{w_{i+1}^{j}-w_{i}^{j}}{h}\right)-EA \left( \dfrac{v_{i+1}^{j}-v_{i}^{j}}{h}\right)\left( \dfrac{w_{i+1}^{j}-2w_{i}^{j}+w_{i-1}^{j}}{h^{2}}\right)-\\
& \dfrac{3}{2}EA\left( \dfrac{w_{i+1}^{j}-w_{i}^{j}}{h}\right)^{2} \left( \dfrac{w_{i+1}^{j}-2w_{i}^{j}+w_{i-1}^{j}}{h^{2}}\right)=f
\end{split}
\end{equation}
the 2nd equation of the system:
\begin{equation}
\begin{split}
& \left(\dfrac{(m_{z}+kc_{2})v_{i}^{j+1}-(2+kc_{2})v_{i}^{j}+v_{i}^{j-1}}{k^{2}}\right)- EA\left( \dfrac{v_{i+1}^{j}-2v_{i}^{j}+v_{i-1}^{j}}{h^{2}}\right) -\\
& EA\left( \dfrac{w_{i+1}^{j}-w_{i}^{j}}{h}\right) \left( \dfrac{w_{i+1}^{j}-2w_{i}^{j}+w_{i-1}^{j}}{h^{2}}\right)=0
\end{split}
\end{equation}
where h is delta x and k is delta t
what should i do next ??am i in the right path ?,, is this a good start or there is something else to do before using finite difference method.
thank you.
 
Last edited:

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