Solving u_x=(sin(x))*(u) in Fourier space

In summary, the conversation is about solving an equation of the type u_x=(sin(x))*(u) on a periodic domain using the fast Fourier transform. The person asking the question is trying to solve for u, where u_x represents the partial derivative of u with respect to x. They have tried using convolutions but have had no success. It is suggested to rewrite the equation as y'=y*sin(x) and solve it as an ordinary differential equation.
  • #1
vector_problems
10
0
Does anyone know if it is possible to solve an equation of the type
u_x=(sin(x))*(u)
on a periodic domain using the fft.

I have tried methods using convolutions but have had no success

thanks in advance
 
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  • #2
vector_problems said:
Does anyone know if it is possible to solve an equation of the type
u_x=(sin(x))*(u)
on a periodic domain using the fft.
What does u_x mean in the context of your problem? It could possibly mean the partial derivative of u with respect to x, or it could mean the x-component of a vector u.

Also, what are you trying to solve for?
vector_problems said:
I have tried methods using convolutions but have had no success

thanks in advance
 
  • #3
sorry, should have been more clear. u_x is the partial derivative of u w.r.t. x and i am trying to solve for u,

du/dx=(sin(x))*(u)
 
  • #4
Is u a function of any variables other than x? If so, your equation is an ordinary differential equation, and one that is separable and easy to solve analytically.
 
  • #5
You have ux=sin(x)*u

Can't you rewrite it as: y'=y*sin(x)? Solve it as ODE and instead of writing the constant, just assume it's a function of the other variables.
 

1. What is Fourier space?

Fourier space is a mathematical concept used in signal processing and analysis. It is a way to represent a signal or function as a sum of sinusoidal waves with different frequencies and amplitudes. This representation allows for easier manipulation and analysis of the signal.

2. How is solving u_x=(sin(x))*(u) in Fourier space different from solving it in the time/space domain?

In the time/space domain, the equation would involve differentiating the function u with respect to x. However, in Fourier space, this differentiation is represented as multiplication by the frequency. This makes the equation easier to solve using algebraic manipulation.

3. Why is solving equations in Fourier space useful for scientists?

Solving equations in Fourier space allows scientists to easily analyze and manipulate signals or functions. It also allows for the separation of different frequency components, which can provide insights into the underlying dynamics of the system being studied.

4. Can any equation be solved in Fourier space?

No, not all equations can be solved in Fourier space. The equation must be linear and the boundary conditions must be compatible with Fourier analysis. Additionally, some equations may become more complicated in Fourier space and may be easier to solve in the time/space domain.

5. Are there any limitations to using Fourier space for solving equations?

One limitation is that the equation must have periodic boundary conditions, meaning that the function repeats itself after a certain interval. Another limitation is that the equation must be linear, which may not accurately describe all systems or phenomena.

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