Question about heat conduction equation.

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Discussion Overview

The discussion revolves around solving a one-dimensional heat conduction equation with specific boundary conditions: one end held at zero temperature and the other end insulated. Participants explore the implications of these conditions on the solution process, particularly focusing on the mathematical interpretation of the insulated boundary.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant expresses familiarity with solving the heat conduction equation under certain conditions but seeks guidance for a case where one end is insulated.
  • Another participant requests the specific equation being solved to provide better assistance.
  • A participant clarifies the heat conduction equation as \(\frac{\partial^2 u}{\partial t} = a^2 \frac{\partial^2 u}{\partial x^2}\) and notes the boundary condition at \(U(0,t)=0\) while questioning what to set \(U(L,t)\) to.
  • There is a correction regarding the form of the heat equation, with a participant suggesting it should be \(\frac{\partial U}{\partial t}=a^2\frac{\partial ^2U}{\partial x^2}\).
  • Another participant interprets the insulated boundary condition at \(x=L\) as implying that the flux at that point is zero, leading to the condition \(\left. \frac{\partial U}{\partial x}\right|_{x=L}=0\).
  • A participant acknowledges their earlier mistakes and expresses confidence in solving the problem after understanding the meaning of 'insulated'.

Areas of Agreement / Disagreement

Participants generally agree on the interpretation of the boundary conditions, particularly the meaning of an insulated end. However, there is some initial confusion regarding the correct form of the heat equation and the specific boundary conditions to apply.

Contextual Notes

There are some limitations in the discussion, such as the initial misunderstanding of the equation's form and the specific mathematical interpretation of the boundary conditions, which may affect the clarity of the solution process.

DrKareem
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I know how to solve a 1-D heat conduction equation when both ends are kept at 0 temperature(using separation of variables and Fourier series.). In the notes, the prof asked us to solve for one end kept at zero and the other insulated (at x=L) and referred to a non-existent chapter in our textbook for the solution. Can someone give me a few pointers on how to proceed? I don't know what to equate U(L,t) to, and that kinda gets u stuck...
 
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Well, firstly, post the equation you're trying to solve!
 
I'm sorry, I (falsely) assumed everyone would recognize the equation i had in mind. The equation is

\frac{\partial^2 u}{\partial t} = a^2 \frac{\partial^2 u}{\partial x^2}

With U(0,t)=0. U(L,t)= ??
 
Last edited:
Firstly, that equation has no function in it! Secondly, are you sure that's the correct expression? I thought the heat equation looked like \frac{\partial U}{\partial t}=a^2\frac{\partial ^2U}{\partial x^2} in one dimension?

Anyway, I think the condition that says that at x=L the rod is insulated, means that the flux at x=L is zero; i.e.\left. \frac{\partial U}{\partial x}\right|_{x=L}=0
 
yes, i made those horrible typos sorry again (been up very early having nothing to do but solve). I will try solving it, i think it should be easy. Thanks for the input.
 
Cristo is right. Saying that one end, x= 0, is held at 0 means, of course, U(0,t)= 0. Saying that the other end, x=L, means that
\frac{\partial U}{\partial x}(L, u)= 0
 
Last edited by a moderator:
Thanks HallsofIvy. I already solved it, and it was easy as expected (i just didn't know the mathematical interpretation of the word 'insulated' in that context).
 

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