Heat equation Definition and 257 Threads

Hi all, I'd like to solve the following problem in 3 dimensions: \partial_t u(r,t) = D\Delta u(r,t) u(r,0) = 0 u(0,t) = C_o In words, I am looking at a point 'source' that is turned on at t=0 and held at constant temperature. The ultimate goal is to then convolve this solution with...

Hi there. At first I tought of posting this thread on the homework category, but this is a conceptual doubt rather than anything else. While revisiting Heat Transfer I stumbled upon a simple problem, that yet got me thinking. It is as follows: Before anything else, let me show...

Hey guys, I am just looking for some online resources for solving the heat equation. So far I have looked at Paul's Online Math Notes: http://tutorial.math.lamar.edu/Classes/DE/SolvingHeatEquation.aspx But I don't feel very confident with the material yet. I would really like some more...

problem u_t=u_xx, x is in [0,1], t>0 with u(0,t)=u(1,t)=0, t>0 u(x,0)=sin(pi*x)-sin(3*pi*x), x is in (0,1) i think its solution is of the form u(x,t)=sigma(n=1 to infinity){a_n*sin(n*pi*x)*exp(-n^2*pi^2*t) where a_n=2*integral(0 to 1){ (sin(pi*x)-sin(3*pi*x)) * sin(n*pi*x) }...

Hello, I am looking to apply to heat equation to a cylindrical rod and solving with explicit finite difference scheme. I have never worked with cylindrical coordinates before, what would be the best way to model this? I am having a hard time understanding the advantage of using cylindrical...

Homework Statement A flat plate lies in the region: 0<x<35, 0<y<inf The temperature is steady (not changing with time), and the boundary conditions are: T = { x if 0<x<35; y=0 70-x if 35<x<70; y=0 0 if x=0 0 if x=70 } Enter the temperature at (x = 42, y = 21) Homework...

Can anyone tell me if there exist analytical solution to the Fourier heat equation rhoCdt/dt= ∇.(k∇T) + S Thanks

Homework Statement hey, i have a heat equation question which asks to solve for u(x,t) given that u(0,t)=Q_0 + ΔQsin(ωt).Homework Equations d_xx u = k d_t u u(0,t)=Q_0 + ΔQsin(ωt) The Attempt at a Solution so you can solve the equation pretty easily with separation of variables, i.e...

Hi everyone, I'm attempting to create a computer program to solve the transient 3d heat equation using the Crank Nicolson method. I would like to model the boundaries of my domain as losing heat via convection and radiation due to the temperature difference between the boundary and the air in...

I've been teaching myself some thermodynamics, and I've been thinking about solving the heat equation. \frac{\partial T}{\partial t} = K\frac{\partial ^2 T}{\partial x^2} I haven't taken a course in PDEs. I have noticed that if I assume an exponential solution, there are not non-decaying...

I am trying to solve the following pde numerically using backward f.d. for time and central difference approximation for x, in MATLAB but i can't get correct results. \frac{\partial u}{\partial t}=\alpha\frac{\partial^{2}u}{\partial x^{2}},\qquad u(x,0)=f(x),\qquad u_{x}(0,t)=0,\qquad...

hello i am solving heat equation in cylindrical coordinator. i am using MATLAB "pdepe" solver to solve the partial differential equation. can anyone suggest me how to choose the initial condition?

Large, cylindrical bales of hay used to feed livestock in the winter months are D = 2 m in diameter and are stored end-to-end in long rows. Microbial energy generation occurs in the hay and can be excessive if the farmer bales the hay in a too-wet condition. Assuming the thermal conductivity of...

Hi everybody, I'm trying to find a solution for the 3D heat equation for pulsed surface heating of a semi-infinte solid with insulated surface. I know the method of reflection is required, and that a point source in an infinite solid gives the following solution: U(x,y,z,t)=...

given the heat equation \frac{\partial u}{\partial x}=\frac{\partial^2 u}{\partial x^2} what does \frac{\partial^2 u}{\partial x^2} represent on a practical, physical level? I am confused because this is not time-space acceleration, but rather a temperature-spacial derivative. thanks all!

Homework Statement For the heat equation in two space variables find all the linear transformations of the form (x,y) = a(x',y') for real number a such that \frac{\partial u}{\partial t} = \frac{k}{\sigma}\Delta u \Leftrightarrow \frac{\partial v}{\partial t} = \Delta'v where u(x,y,t) =...

Have been trying for hours but simply no results. Hope that someone can help me out. \[\frac{\partial u}{\partial t}=4\frac{\partial^2 u}{\partial x^2}\] for \(t>0\) and \(0\leq x\leq 2\) subject to the boundary conditions \[u_x (0,t) = 0\mbox{ and }u(2,t) = 0\] and the initial condition...

Homework Statement I'm unable to solve a problem of heat equation in a cylinder in steady state. The problem is a cylinder of radius a and a height L. The boundary condition are ##T(\rho , \theta , 0)=\alpha \sin \theta##, ##T(\rho, \theta , L)=0## and ##\frac{\partial T}{\partial \rho} (a...

Homework Statement Problem 8-19 in Matthews and Walker's book on mathematical physics. A straight wire of radius a is immersed in an infinite volume of liquid. Initially the wire and the liquid have temperature T=0. At time t=0, the wire is suddenly raised to temperature ##T_0## and...

1. Solve the Heat equation u_t = ku_xx for 0 < x < ∏, t > 0 with the initial condition u(x, 0) = 1 + 2sinx and the boundary conditions u(0, t) = u(∏, t) = 1 (Notice that the boundary condition is not homogeneous) 3. Find the solution of the Wave equation u_tt = 4 u_xx with u(0...

Hello there, I want to solve the heat PDE in a 1D domain for a source moving at constant speed. The problem has been solved already, the solution being stationary in a reference frame moving with the source. This is highly un-intuitive, and I suppose the result originate from the fact the...

The heat equation predicts that heat spreads infinitely far over arbitrarily small time intervals. What happens in real life? How does the heat equation get modified?

Hi! I have some trouble understanding this question. Could someone help me with it? Thanks! Solve the following with the explicit method from t=0 to t=0.5 with h=1/10 and with μ(=k/h2)=0.5 ut = uxx, -1 ≤ x ≤ 1, t>0 u(0,x) = cos(x), -1 ≤ x ≤ 1 u(t,-1) = u(t,1) = e-tcos1, t>0 Compute...

Homework Statement The question was way too long so i took a snap shot of it http://sphotos-h.ak.fbcdn.net/hphotos-ak-snc7/397320_358155177605479_1440801198_n.jpg Homework Equations The equations are all included in the snapshotThe Attempt at a Solution So for question A I've done what the...

Homework Statement Show that if u(x,t) and v(x,t) are solutions to the Dirichlet problems for the Heat equation u_t (x,t) - ku_xx (x,t) = f(x,t), u(x,0) = Φ₁(x), u(0,t) = u(1,t) = g₁(t) v_t (x,t) - kv_xx (x,t) = f(x,t), v(x,0) = Φ₂(x), v(0,t) = v(1,t) = g₂(t) and if Φ₂(x) ≤ Φ₁(x)...

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...

Is this correct? $$ \text{B.C.}=\begin{cases} T_x(0,t) = 0\\ T(\pi,t) = 1 \end{cases} $$ The I.C. is $T(x,0) = 0$. The equation is $\frac{1}{\alpha}T_t = T_{xx}$.$$ \varphi(x) = A\cos\lambda x + B\frac{\sin\lambda x}{\lambda} $$ and $$ \psi(t) = C\exp\left(-\alpha\lambda^2t\right). $$ First...

Homework Statement By trial and error, find a solution of the diffusion equation du/dt = d^2u / dx^2 with the initial condition u(x, 0) = x^2. Homework Equations The Attempt at a Solution Given the initial condition, I tried finding a solution at the steady state (du/dt=0)...

Homework Statement I have a quiz question that I'm struggling with. We've been working on using a FTCS scheme with two Essential Boundary Conditions, and now I have a problem with one EBC (ie static) and a Natural Boundary Condition (ie a derivative). The condensed problem statement: u_{t} =...

Homework Statement Solve u_t -k u_xx +V u_x=0 With the initial condition, u(x,0)=f(x) Use the transformation y=x-Vt Homework Equations The solution to the equation u_t - k u_xx=0 with the initial condition is u(x,t)=1/Sqrt[4\pi kt] \int e^(-(x-y)^2 /4kt)f(y) dy The Attempt at a...

I have a project where I need to solve T''(x) = bT^4 ; 0<=x<=1 T(0) = 1 T'(1) = 0 using finite differences to generate a system of equations in Matlab and solve the system to find the solution So far I have: (using centred 2nd degree finite difference) T''(x) = (T(x+h) - 2T(x) +...

Hello Folks, I have this equation to solve (expressed in LaTeX): \frac{\partial{h}}{\partial t} = \frac{1}{n} \left[ \frac{1}{r^2 \sin^2{\phi}} \frac{\partial}{\partial \theta} \left( K \frac{\partial h}{\partial \theta} \right) + \frac{1}{r^2 \sin \phi} \frac{\partial}{\partial \phi}...

Homework Statement Suppose that u(x,t) satisfies the heat equation u_{t}=u_{x x} for 0<x<L and t>0 with initial condition u(x,0)=θ(x) and boundary conditions u(0,t)=u(L,t)=0. Suppose that θ(x)>0 for 0<x<L. Explain why u(x,t)>0 for all 0<x<L and t>0 Homework Equations Strong Maximum principle...

Homework Statement I have boundary conditions on my heat equation ## \dot{T}(x,t) = T''(x,t) ## ## T(0,t) = T(L,t), ## ## \frac{\partial T(0,t)}{\partial x} = \frac{\partial T(L,t)}{\partial x} ## Then at ## T= 0## ## T(x,0) = 1 ## for ## 0<x<L/4 ## ## T(x,0) = 0 ## for ## L/4<x<L ##...

Homework Statement vt(x,t)=vxx(x,t) + p(x,t), Neumann boundary conditions, v(x,0)=cos(∏x) Homework Equations Assume v(x,t)=X(x)T(t) The Attempt at a Solution I'm stuck. We aren't given a p(x,t) and I'm not sure what to do. Where do I go from here? Attempt so far:

Hi, So if I start with the boundary conditions U(0,t) = T1 and U(L,t) = T2 and T1 does not equal T2, it seems that you are supposed to look at the 'steady state solution' (solution as t goes to infinity)? which satisfies T''(x) = 0 so the solutions are T(x) = Ax + B and then you...

Heat Equation (Non Homogeneous BCs) - Difficult Laplace Transform... help! ;) Hi I'm trying to model the temperature profile of an inertia friction welding during and after welding. I have the welding outputs and have come up with a net heat flow wrt time during the process. I now want to...

Conduction - Heat Equation - Units Don't Add Up! Hi there I have what I think/hope is a simple question: I've been working on heat inputs and outputs in inertia friction welds and have managed to produce a net power term (W) as a function of time. I now want to use that in the heat...

Homework Statement F(x,t) satisfies \frac{\partial^2 F(x,t)}{\partial x^2}=\frac{\partial F(x,t)}{\partial t} With the following boundary conditions \frac{\partial F(0,t)}{\partial x}=\frac{\partial F(1,t)}{\partial x} F(0,t) = F(1,t) F(x,0) = x^2 \text{ for } x \in (0,1) The...

http://img821.imageshack.us/img821/7901/heatp.png Uploaded with ImageShack.us I'm having difficulty with the boundary conditions on this problem. I don't need a solution or a step by step. I've just never solved a boundary condition like this. Its the u(pi,t) = cos(t) that is giving me...

Solve $\begin{aligned} & {{u}_{tt}}={{u}_{xx}},\text{ }x\in [0,1],\text{ }t>0, \\ & u(x,0)=f(x), \\ & {{u}_{t}}(x,0)=0,\text{ }u(0,t)=u(1,t)=0 \\ \end{aligned} $ where $f(x)$ is defined by $f(x)=x$ if $0\le x\le \dfrac12$ and $f(x)=1-x$ if $\dfrac12\le x\le1.$ I'm not sure how to...

Homework Statement The original problem is to solve u_t=u_xx+x with u(x,0)=0 and u(0,t)=0 by assuming there is a solution t^a*u(r), where r=x/t^b and a,b are constants Homework Equations The Attempt at a Solution This is a long problem, so I'm not writing everything. Following the...

Homework Statement Problem 8-17 from Mathew's and Walker's book: Use a cosine transform with respect to y to find the steady-state temperature distribution in a semi-infinite solid x>0 when the temperature on the surface x=0 is unity for -a<y<a and zero outside this strip. Homework...

Hi! I need to find out how to solve this type of heat equations: $$\large \frac{du}{dt} - \frac{d^2u}{dx^2} = \sin \pi x$$ $$\large u|_{t=0} = \sin 2\pi x $$ $$\large \large u|_{x=0} = u|_{x=1} = 0$$ I know what the solution to this but I can't solve it myself. The problem is that all over...

Homework Statement Determine the equilibrium temperature distribution for a one-dimensional rod composed of two different materials in perfect thermal contact at x=1. For 0<x<1, there is one material (cp=1, K0=1) with a constant source (Q=1), whereas for the other 1<x<2 there are no sources...

Homework Statement Find a formal solution of the heat equation u_t=u_xx subject to the following: u(0,t)=0 u_x(∏,t)=0 u(x,0)=f(x) for 0≤x≤∏ and t≥0 Homework Equations u(x,t)=X(x)T(t)The Attempt at a Solution I first began with a separation of variables. T'(t)=λT(t) T(t) =...

1 .) i added several problems which i couldn't understand the approach for solving them. i'm kinda confused, will glad if someone would guide me. 2.) in class we've talked about and calculated . n orders(0,1,2,3) of moments, how is it to do with the heat equations? and what is the...

Hi everyone, I am wondering if the heat equation is valid for compressible fluids like air. This is assuming constant 100% humidity. If it is not then how close is the appoximation. The model assumes that heat moves through an array of air only by conduction. At the moment I use a...

Homework Statement Solve the heat equation u_t=u_{xx}+u_{yy} fot t>0 in the first quadrant of \mathbb{R}^2. The boundary conditions are u(0,y,t)=u(x,0,t)=0 and the initial temperature distribution is f(x,y)= \begin{cases} 1 \;\;\;\; \text{in the square } \; 0<x<1; \; 0<y<1 \\ 0 \;\;\;\...

A 3 kW kettle contains 2.0 kg of water at a temperature close to 100oC. Latent heat of vaporisation for water: Lv=2256 (kJ kg^-1) Q= Lv x mass Ok I understand this problem because I now the answer but I don't understand the process. Like my teacher wrote 2256x10^3 why he wrote...