Equilibrium Soln for $u_{t}=K u_{xx}+\gamma$

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Discussion Overview

The discussion revolves around finding the equilibrium solution for the partial differential equation given by $u_{t}=K u_{xx}+\gamma$, within specified boundary conditions. Participants explore the mathematical formulation and implications of the problem, including the role of boundary conditions and integration constants.

Discussion Character

  • Mathematical reasoning
  • Technical explanation
  • Homework-related

Main Points Raised

  • One participant presents the equation and boundary conditions, expressing uncertainty about how to proceed with finding the equilibrium solution.
  • Another participant suggests setting the time derivative to zero to find the equilibrium solution, leading to the equation $0=Ku_{xx}+\gamma$.
  • A participant proposes a specific form for the solution, $u(x)=-\dfrac\gamma{2K} x^2$, and questions whether this makes sense in the context of the problem.
  • There is a discussion about the boundary conditions and why they do not include the time parameter, indicating a shift to an equilibrium state.
  • Concerns are raised about the necessity of a constant of integration in the proposed solution, suggesting that initial conditions may need to be applied.

Areas of Agreement / Disagreement

The discussion remains unresolved, with participants expressing differing views on the correctness of the proposed solution and the treatment of boundary conditions and integration constants.

Contextual Notes

Participants have not fully clarified the assumptions underlying their approaches, particularly regarding the integration constants and the implications of the boundary conditions in the context of equilibrium solutions.

Markov2
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Well I don't know if is the correct term for this for here goes:

Let

$\begin{align}
& {{u}_{t}}=K{{u}_{xx}}+\gamma ,\text{ }0<x<L,\text{ }t>0, \\
& u(0,t)=\alpha ,\text{ }u(L,t)=\beta ,\text{ }t>0, \\
& u(x,0)=0,
\end{align}
$

where $\alpha,\beta,\gamma$ are constant, then find the equilibrium solution. I don't know what I need to do.
 
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Markov said:
Well I don't know if is the correct term for this for here goes:

Let

$\begin{align}
& {{u}_{t}}=K{{u}_{xx}}+\gamma ,\text{ }0<x<L,\text{ }t>0, \\
& u(0,t)=\alpha ,\text{ }u(L,t)=\beta ,\text{ }t>0, \\
& u(x,0)=0,
\end{align}
$

where $\alpha,\beta,\gamma$ are constant, then find the equilibrium solution. I don't know what I need to do.

To find the equilibrium solution $U(x)$, set

$0=Ku_{xx}+\gamma$
$U(0)=\alpha$
$U(L)=\beta$
 
So I get $u(x)=-\dfrac\gamma{2K} x^2,$ does this make sense? Why the boundary conditions aren't something like $u(0,t)$ ?
 
Markov said:
Why the boundary conditions aren't something like $u(0,t)$ ?

We removed the t parameter.

---------- Post added at 02:45 PM ---------- Previous post was at 02:43 PM ----------

Markov said:
So I get $u(x)=-\dfrac\gamma{2K} x^2,$ does this make sense?

Shouldn't you have a constant of integration?
 
dwsmith said:
Shouldn't you have a constant of integration?
Oh yes, yes, so then I just put the initial conditions and that's it?
 

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