Discretization Definition and 30 Threads

I have a PDE to solve numerically on the region ##x \in [0,1]## and ##t \in (0, \infty)##. It is of the form:$$\frac{\partial f(x,t)}{\partial t} = g(x,t) + \int_0^1 h(x, x') f(x', t) dx'$$The second term is the tricky part. The change in ##f(x,t)## at ##x## depends on the value ##f(x',t)## of...

Hello, I want to model the thermal behaviour of a moving heat transfer fluid in 1D, with convective exchanges with the walls. I have obtained the following equation (1 on the figure). I have performed a second order spatial discretization with decentred schemes at the extremities (y = 0 and H)...

Mathematicians, I summon thee to help me identify which field deals with this stuff. I come here not as a physicist but as a sunday programmer trying to solve some numerical problems. I set out to model a lattice version of a smooth space. A discretization procedure not uncommon in physics, but...

Hi. I have this PDE that governs an L x L plate (similar to the Poisson equation, it seems) with boundary conditions F = 0 and F" = 0 along the edges. I have successfully solved the problem by setting up an equality W = ∇2F then I solved the two PDEs simultaneously: W = ∇2F (boundary...

Hi. Been a while since I logged in here, I missed this place. Anyway, I have a question (title). Is that even possible? Say for example I have the standard heat equation (PDE) subject to the boundary conditions: T(0,t) = To T(∞,t) = Ti And the initial condition: T(0,t) = Ti I am aware of how...

Homework Statement [/B] Derive a discrete formula for an RC circuit for Vab[k] using the forward difference approximation. It should be of the form Vab[k + 1] = α Vab[k], and depend only on T, R, and C. For T = 0.076 s, R = 3 kΩ, and C = 10 mF, what is α? T is the period. The current is going...

Hi, I know the general form of the Navier Stokes Equation as follows. I am following a software paper of "Gerris flow solver written by Prof. S.Popinet" [Link:http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.374.5979&rep=rep1&type=pdf] and he mentions after time discretization he ends...

Homework Statement Consider the differential equation \begin{equation} y'''-y''=u \end{equation} Discretize (1) using a forward-Euler scheme with sampling period \begin{equation} \Delta=1 \end{equation} and find the transfer function between u(k) and y(k) Homework Equations The Euler method is...

Homework Statement Hi - I'm on the last chapter of this book and am a bit stuck. I am given a very basic fortran program (code attached in the zip file) and asked to 'investigate its accuracy and stability, for various values of Δt and lattice spacings'. The program is an implementation of the...

Hi, I want to transform a complex exponential with quadratic phase to discrete form, in other words to a vector form. can anyone help me with that? Thanks

Hello, I am trying to solve the following differential equation in a tri-dimensional grid with grid spacing of hx , hy , and hz along the x, y, and z coordinates. \begin{equation}\nabla\cdot(\epsilon\nabla\phi)=-4\pi\rho\end{equation} Here, ε is a scalar quantity that is a function of x, y...

How can I use finite difference to discretize a system of fourth order differential equations? for example: y(4)+5y(3)-2y''+3y'-y=0

Hi!, I'm working on a personal project: Solve the heat equation with the semi discretization method, using my own Mathematica's code, (W. Mathematica 9). The code: I'm having problems with the variable M (the number of steps). It works with M=1-5, but no further, I do not know what's going...

I am setting up a numerical simulation from a 2D discretization of the heat equation in cylindrical coordinates. my spatial variables are radius (r), height (z), and azimuth (ø). The assumption is that there is no gradient along the azimuth direction (if temperature is T then dT/dø = 0)...

Hi, I would like to solve the steady-state incompressible Navier-Stokes equations by a spectral method. When I saw the classic primitive-variable finite element discretization of the time-dependent incompressible N-S, it turned out that the coefficient matrix of the derivatives of the unknowns...

So figuratively, I'm trying to win a nuclear war with a stick. :smile: I did not take any course in PDEs, I just self-studied some of them, and now I'm toast. :smile: First, please feel free to hurl rocks at me if my simplification is incorrect...

I have quite a naive question, which doesn't really go deep into physics/mathematics.. :) Let's take seriously the idea that space is continuous. The questions is, how are we able to move in such a space? We know that in a continuous space (real numbers), between two points there are...

Hi all, It may be a trivial question. But, if I have a PDE of variable u(x,t) -------------------------------- \dot{u} = f(u,\partial_x{u},..) with boundary condition : u(0,t) = u(L,t) =0. -------------------------------- Now I need to calculate \partial_x{u} for that can I define the...

Hi all, I want to use SPH discretization for my cooling rate but i don't know if its valid. So, this is the equation i want to discretize. L = (1/dT/dt) . ∫v(T) dT So, dT/dt = (1/L) . ∫v(T) dT dT/dt = (1/L). Ʃv(T) dT (with dT →0) The limits of the above integral are...

Hi all, I am trying to figure out 1) What to call my problem so I can better research the literature, and 2) see if anyone here knows of a solution. Essentially, I have a large set of f(x) vs x points (~20,000) which I need to split into subdomains in x, and within each subdomain...

I work with a grid-based code, this means that all of my quantities are defined on a mesh. I need to compute, for every point of the mesh the divergence of the velocity field. All I have is, for every cell of my mesh, the values of the 3-d velocity in his 26 neighbors. I call neighbors the...

Hi guys I was wondering if anyone on here could help me out. Essentially I am trying to build a higher order cfd code and struggling to work out where to start, I’m trying to build it using polynomial fitting so here’s my problem. Taking my domain as...

Hi. I have a few questions about sensor specifications and its implementation in a Kalman Filter and simulation of gyroscope/accelerometer output. Abbreviation used: d - discrete c - continuous Q1: From book: Aided Navigation - Farrell (you don't need the book to understand the...

Hi everybody, I hope I am asking in the right forum. Let describe the problem as follows: I have a 1D heat equation. To solve it, I use finite-difference method to discretize the PDE and obtain a set of N ODEs. The larger N gives the better solution, i.e., the closer the solution to the...

My QM is undergrad level and I don't keep up on recent breakthroughs. I'm curious what the status is on space structure. This article (Mecklenburg, 2011) uses the phrase "hidden substructure" http://prl.aps.org/abstract/PRL/v106/i11/e116803 is it similar to Zurek, 2001? "structure on...

What is a finite-difference discretization for the partial differential term: \frac{\partial^4\phi}{\partial x^2\partial y^2} Thanks in advance.

1. Hi, I am trying to model the magnetic force between two cylindrical identical sized permanent magnets. I am using the Charge/Coulombian model to do this. This assumes that all of the "magnetic charge" is on the pole ends of the magnet, i.e. the flat surfaces at the top and bottom of each...

I just learned about L and Lz, I can accept the fact that L is discreted in quantum world, but it does not make sense at all for me that Lz too is bound in term of m multiple. I mean, if we choose an axis that is tilted just a little bit, then our value for Lz changes immideately and m is not an...

Homework Statement Consider a 1D sample, such that for x < xb the semiconductor has a dielectric constant \varepsilon_{1}, and for x > xb has a dielectric constant \varepsilon_{2}. At the interface between the two semiconductor matierials (x = xb) there are no interface charges. Starting...

If I have a logged temperature change over time which makes up a plottet graph. I denote this change {{dT} \over {dt}} People have told me this can be solved using discretization, but I have no idea what that is. Apparently it is something like this: {{T_1 - T_2 } \over {\Delta...