Solving the Heat Equation with Initial Conditions

In summary, the heat equation with initial conditions is a mathematical model used to describe the distribution of heat over time in a system. It is solved using various mathematical techniques and takes into account the initial temperature and material properties of the system. Boundary conditions, such as temperature at the boundaries, are incorporated into the solution to accurately describe the behavior of the system. This equation has many applications in fields such as engineering, physics, and chemistry.
  • #1
Dustinsfl
2,281
5
I have already solved the main portions.
I have
$$
T(x,t) = \sum_{n = 1}^{\infty}A_n\cos\lambda_n x\exp(-\lambda_n^2t)
$$
The eigenvalues are determined by
$$
\tan\lambda_n = \frac{1}{\lambda_n}
$$
The initial condition is $T(x,0) =1$.
For the particular case of $f(x) = 1$, numerically determine the series coefficients $A_n$ and construct a series representation for $T(x,t)$.
How do I do this?
$$
A_n = 2\int_0^1\cos\lambda_n xdx
$$
 
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  • #2
dwsmith said:
I have already solved the main portions.
I have
$$
T(x,t) = \sum_{n = 1}^{\infty}A_n\cos\lambda_n x\exp(-\lambda_n^2t)
$$
The eigenvalues are determined by
$$
\tan\lambda_n = \frac{1}{\lambda_n}
$$
The initial condition is $T(x,0) =1$.
For the particular case of $f(x) = 1$, numerically determine the series coefficients $A_n$ and construct a series representation for $T(x,t)$.
How do I do this?
$$
A_n = 2\int_0^1\cos\lambda_n xdx
$$
$$
\begin{alignat*}{3}
T(x,t) & = & 1.7624\cos(0.86x)e^{-0.86^2t} - 0.1638\cos(3.426x)e^{-3.426^2t} + 0.476\cos(6.437x)e^{6.437^2t}\\
& - & 0.0218\cos(9.529x)e^{-9.529^2t} + 0.0124\cos(12.645x)e^{-12.645^2t} - 0.0080\cos(15.771x)e^{-15.771^2t}\\
& + & 0.0055\cos(18.902x)e^{-18.902^2t} - 0.0041\cos(22.036x)e^{-22.036^2t} + 0.0031\cos(25.172x)e^{-25.172^2t}\\
& - & 0.0025\cos(38.31x)e^{-28.31^2t}
\end{alignat*}
$$
 
  • #3
dwsmith said:
I have already solved the main portions.
I have
$$
T(x,t) = \sum_{n = 1}^{\infty}A_n\cos\lambda_n x\exp(-\lambda_n^2t)
$$
The eigenvalues are determined by
$$
\tan\lambda_n = \frac{1}{\lambda_n}
$$
The initial condition is $T(x,0) =1$.
For the particular case of $f(x) = 1$, numerically determine the series coefficients $A_n$ and construct a series representation for $T(x,t)$.
How do I do this?
$$
A_n = 2\int_0^1\cos\lambda_n xdx
$$

Hi dwsmith, :)

Can you please clarify as to what \(f\) is?

Kind Regards,
Sudharaka.
 
  • #4
My guess is the initial condition since $f$ is usually denoted as an arbitrary IC.
 
  • #5
dwsmith said:
How do I do this?
$$
A_n = 2\int_0^1\cos\lambda_n xdx
$$

\[A_n=2\int_0^1\cos\lambda_n xdx=\left.\frac{2\sin\lambda_n x}{\lambda_n}\right|_{0}^{1}=\frac{2\sin\lambda_n}{\lambda_n}\]

dwsmith said:
$$
\begin{alignat*}{3}
T(x,t) & = & 1.7624\cos(0.86x)e^{-0.86^2t} - 0.1638\cos(3.426x)e^{-3.426^2t} + 0.476\cos(6.437x)e^{6.437^2t}\\
& - & 0.0218\cos(9.529x)e^{-9.529^2t} + 0.0124\cos(12.645x)e^{-12.645^2t} - 0.0080\cos(15.771x)e^{-15.771^2t}\\
& + & 0.0055\cos(18.902x)e^{-18.902^2t} - 0.0041\cos(22.036x)e^{-22.036^2t} + 0.0031\cos(25.172x)e^{-25.172^2t}\\
& - & 0.0025\cos(38.31x)e^{-28.31^2t}
\end{alignat*}
$$

I don't understand why you wrote this. Did you obtain this by simplifying the series mentioned in your first post?
 
  • #6
That is the series with the eigenvalues obtain from Desmos of the first 10 positive of $\tan x = \frac{1}{x}$.
 

FAQ: Solving the Heat Equation with Initial Conditions

What is the heat equation with initial conditions?

The heat equation with initial conditions is a mathematical model that describes how heat is distributed over time in a given system. It takes into account the initial conditions of temperature and the material properties of the system.

How is the heat equation with initial conditions solved?

The heat equation with initial conditions is solved using various mathematical techniques such as separation of variables, Fourier series, and numerical methods. Different methods may be used depending on the complexity of the system and the desired level of accuracy.

What are the initial conditions in the heat equation?

The initial conditions in the heat equation refer to the temperature distribution at the beginning of the system. This includes the initial temperature at different points in the system as well as the initial rate of change of temperature, also known as the initial gradient.

How are boundary conditions incorporated into the solution of the heat equation with initial conditions?

Boundary conditions, such as the temperature at the boundaries of the system, are incorporated into the solution of the heat equation by setting up appropriate equations based on the physical properties of the system. These boundary conditions help to define the behavior of the system and are essential for obtaining an accurate solution.

What are some real-world applications of solving the heat equation with initial conditions?

The heat equation with initial conditions has a wide range of applications in various fields such as engineering, physics, and chemistry. Some examples include predicting the temperature distribution in a material during manufacturing processes, analyzing the thermal behavior of buildings, and understanding the heat transfer in chemical reactions.

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