A pde question that contains fourier series

In summary, the speaker has been struggling to solve a PDE problem for three days and is now feeling overwhelmed. They are seeking help with the problem, which involves solving for u(x,y) given certain initial and boundary conditions, as well as a differential equation. They have tried different approaches but have not been successful. They mention that when a certain parameter is set to 0, the equations become linear, but they are unsure of how to proceed from there.
  • #1
bcyalcin
3
0
i have been trying to solve a pde problem for 3 days but i couldn't even find the answer,now i feel i m about to have a mental disease,anyone can help me ?the question is

u(x,0) = x

u(x,2) = 0

u(0,y) = 0

d u(1,y) / dx = 0
[ d^2 u / dx^2 ] + [ d^2 u / dy^2 ] = 0

i will really be appreciate if someone help me,for long time i have been working on this
p.s. i have tried for k > 0 and k < 0 but couldn't find anything,the only thing about what happens when k = 0 is we obtain linear equations like F(x) = Ax + B and G(y) = Cy + D,but i have no idea what i wil do in Fourier series with these
 
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  • #2
bcyalcin said:
i have been trying to solve a pde problem for 3 days but i couldn't even find the answer,now i feel i m about to have a mental disease,anyone can help me ?


the question is

u(x,0) = x

u(x,2) = 0

u(0,y) = 0

d u(1,y) / dx = 0



[ d^2 u / dx^2 ] + [ d^2 u / dy^2 ] = 0




i will really be appreciate if someone help me,for long time i have been working on this



p.s. i have tried for k > 0 and k < 0 but couldn't find anything,the only thing about what happens when k = 0 is we obtain linear equations like F(x) = Ax + B and G(y) = Cy + D,but i have no idea what i wil do in Fourier series with these

If ##U(x,y) = X(x)Y(y)## your X eigenvalue problem becomes$$
X'' - \lambda X = 0, X(0) = 0, X'(1) = 0$$If you let ##\lambda = -\mu^2##, you should find nonzero eigenvalues.
 

FAQ: A pde question that contains fourier series

What is a PDE?

A PDE, or partial differential equation, is a mathematical equation that involves partial derivatives of a function. It describes how a function changes over multiple variables.

What is a Fourier series?

A Fourier series is a mathematical representation of a function as a sum of trigonometric functions (sine and cosine) that have different frequencies and amplitudes. It is often used to solve PDEs.

How are PDEs and Fourier series related?

Fourier series can be used to solve PDEs by representing the solution as a combination of trigonometric functions. This allows for the use of boundary conditions to find specific solutions to the PDE.

What is the importance of using Fourier series in solving PDEs?

Fourier series provide an efficient way to solve PDEs, especially in cases where the solution is periodic. They also allow for the representation of complex functions as a combination of simpler trigonometric functions, making it easier to analyze and manipulate the solutions.

Are there any limitations to using Fourier series for solving PDEs?

Fourier series may not be applicable to all types of PDEs, particularly those with irregular or discontinuous boundary conditions. In these cases, other methods, such as numerical methods, may be more suitable for finding solutions.

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