Questions tagged [grid]
The grid tag has no usage guidance.
38
questions
3
votes
0answers
56 views
What is the reason for this finite-difference high errors on non-uniform grid?
tl;dr
Using a Taylor-matched method to find coefficients for the discretized equation $ \mathbf{A} \vec{f}'' = \mathbf{B} \vec{f} $, a Fortran code has been implemented to find the second derivative ...
0
votes
1answer
53 views
Is it possible to resample grid in such a way so that continuous objects remain continuous?
Suppose I rasterize a rectangle of width 2.5 gridpoints and get the values as shown:
===============
| 0 | 1 | 1 | 0.5 | 0 |
Now I resample that ...
1
vote
0answers
23 views
Solution errors when refining a static grid: Continuous vs. step-wise refinement
Let's assume I am working on a 2-D domain on $R^2$, with my coordinates $x \in[-1,1]$, $y \in[-1,1]$ and I want to solve a popular CFD problem, like the shallow water system or the Euler system.
At $x=...
0
votes
0answers
32 views
Grids for atmosphere simulation with finite volumes on the globe
I am currently in the early construction process of building a simple CFD model of a rotating planetary atmosphere. The planet should be allowed to tilt significantly, so that a time-dependent source ...
0
votes
1answer
92 views
Good C, C++ library for efficient grid search / tuples, ideally with bindings to Eigen
I have a $q$-dimensional grid, known at run, not compile-time, that has $50$ points in each direction and hence $50^3$ combinations that I would like to first build and then call a function with each ...
1
vote
0answers
17 views
Translating grid with extrusion speed
I am putting into MATLAB code the equations that describe a plastic extrusion process. From a paper, I found I should use a spatial grid that translates with the extrusion speed, being the reference ...
3
votes
0answers
99 views
WENO5 scheme in a staggered grid
I'm trying to use the finite-difference WENO scheme to solve the 2D density conservation law with axial symmetry (coordinates $r,z$):
$\frac{\partial \rho}{\partial t}+\nabla \cdot (\rho \vec{v}) = \...
1
vote
1answer
183 views
Mapping derivative information in uniform to non-uniform grid
I'm having two sets of grids. One is uniform and another one is not uniform. I will calculate the derivative in uniform grid points and I like to transfer(map) the derivative to the non-uniform grid ...
1
vote
1answer
86 views
Grid dependence of a numerical model
Statement of the problem
Suppose, we consider the following model
$$
\begin{array}{l}
(1)~\mathbf{u}_t + \mathbf{F(u)}_x = \mathbf{S}(\mathbf{u},\mathbf{w}), \\
(2)~\mathbf{w}_x = \mathbf{P}(\mathbf{...
1
vote
2answers
64 views
Access optimized data structure for representing integer lattice
Consider the integer lattice in $2d$, namely the set $\mathbb{Z}^2 = \{(x,y): x,y\in \mathbb{Z}\}$, and let $u:\mathbb{Z}^2 \to \mathbb{R} $ be a function defined on some bounded subset of $\mathbb{Z}^...
2
votes
1answer
1k views
Three dimensional irregular grid data interpolation to regular grid
I have three-dimensional radar reflectivity data obtained as voxels (scans, rays, altitudes). The data has been sampled at irregular spacings and I want to convert this into a regular grid. In ...
0
votes
1answer
35 views
Converting mass density to point mass approximation on a grid
In an nbody gravity simulation, instead of doing exact(all-pair brute force) solution, I added masses of each body into cells of a 3D grid(each cell is just a float value having a mass value). Then ...
1
vote
0answers
96 views
Choice of velocity grid - staggered or not?
I'm trying to understand when and why one would use a staggered vs. a colocated grid in problems that have velocities and scalars that they transport (e.e. density).
If scalars are defined cell-...
1
vote
0answers
56 views
adaptive / smart grid choice for dynamic programming
I've a read a paper about investing where they used a dynamic programming approach to solve a finite horizon problem, i.e.
$$\max_{x_t} E[u(W_T)] $$
where $u$ is a utility function and $W_T$ ...
1
vote
2answers
149 views
Grid mapping from Tchebyshev
I am using Tchebyshev discretization to solve a system of PDEs.
Usually, I map the Tchebyshev space($\xi$, from -1 to 1) to physical space ($x$, from 0 to L) using $$x = (\xi +1)*L/2$$
Now, I also ...
2
votes
2answers
62 views
Efficient Representation of (spatially sparse) spatial time series
Background
I have a huge dataset consisting of points (on a plane) together with a timestamp for each point. This is a collection of car GPS measures, giving us the location (latitude/longitude) of ...
0
votes
1answer
47 views
Balancing core load when number of particles in cells vary (PIC on GPU)
Consider this basic scheme for particle in cell simulations ( with just short-range interactions ):
assign particles to disjunct cells
for cell $A$ go over neighboring cells $B$
for each particle $...
1
vote
1answer
297 views
Finite Volume Polar Discretization: Lengths
Given a uniform polar grid, as in the figure below:
and a FV discretization of a gradient for example:
$\frac{\partial p}{\partial \varphi} = 0$
$\Delta r \frac{p_e - p_w}{\Delta \varphi} = 0$
My ...
5
votes
0answers
155 views
How to optimally choose points for multivariable Hermite interpolation?
I have a multi-variate, continuous function $f$ from $R^n$ to $R$, which I can query for its output for any input.
I would like to create interpolation polynomial for it.
In one-dimensional case ...
0
votes
2answers
584 views
Finite Difference Grid Spacing and Scaling
I have been exploring finite differences and heat transfer using the 2D heat equation to further expand my knowledge. So far I think it is going well.
I am running into some confusion around grid ...
1
vote
1answer
2k views
Is there an advantage of using a staggered grid over a regular one when combined with high order methods?
The title says is all. This question is in the contest of an incompressible Navier-Stokes solver.
Specifically, I am currently working on a new solver while referring myself to an older code for ...
0
votes
1answer
549 views
Interpolation of velocities on staggered grid (in PIC)
Edit: (copying from my comment)
Let's consider the inverse problem when I need to transfer velocities from particles to the grid (inverse bilinear interpolation). How'd I transfer a particle's x-...
1
vote
0answers
135 views
C1 continuous spline on regular 2D-grid with quadratic 1D cuts
I want some scalar spline function defined on regular 2D grid $F(x,y)$ with continuous first derivative which is easy to intersect with arbitrary ray/line ${\vec l}(t) = (c_x t,c_y t,c_z t)$.
...
3
votes
1answer
116 views
Alternative to messy grid node indexing within multiple layers of loops
Recently,I dive into a set of somehow ancient Fortran codes and try to fully understand them. A large fraction of these codes are multiple layers of loops over many state variable dimensions, which ...
1
vote
1answer
423 views
3-dimensional plotting with nonuniform grids
I have 3 variables I am considering: time (t), 1-dimensional space (x), and intensity (I). I would like to plot the intensity in the z-axis as a function of t and x (the latter two variables would ...
2
votes
1answer
2k views
Contour plot interpolation recommendation
I am not sure if my question is on topic or not and if not please let me know. I have regularly spaced gridded data(output of a weather forecast simulation software) and I have latitude and ...
1
vote
0answers
119 views
Finding boundary intersection points with Cartesian grid?
I would like to find the intersection points e.g. $M_x$ and $M_y$ as in the attached figure. The boundary (solid line) is defined by the Lagrangian points.
I am working in C++ (basic - medium ...
1
vote
1answer
83 views
Common nodes in two FEM grids
There are two independent tetrahedral FEM grids. Second grid is subset of the first. By subset, I mean: nodes from the second grid are exactly in the same positions as some nodes from the first grid. ...
3
votes
1answer
742 views
Generating a non-uniform grid
I am interested in generating a 1D non-uniform grid on the interval [0, L] with N points, where a region of width $\sigma$ and ...
0
votes
1answer
863 views
Quadtree type Grid
I would like to code for a quadtree type meshing but don't know how to do. If anyone can help or can share any starting code?
10
votes
5answers
7k views
Dynamically ending ODE integration in SciPy
I have a light ray moving through space-time, i.e. a curve in $\mathbb{R}^4$, parametrized by some variable λ. The exact trajectory, i.e. the coordinate functions $x^μ(λ)$ of the curve are given by ...
0
votes
1answer
59 views
Should I use bestman2 or dcache CLIs (srmping, srmls, etc..)
I am fairly new to using SRM, and I am wondering if I should be using srm CLI tools (srmping, srmls, srmcp, etc..) provided by dcache, or bestman2 counter parts (srm-ping, srm-ls).
I used to think ...
1
vote
1answer
250 views
How to compute the weight matrix for tomography applications?
I am trying to compute the weight matrix for a set of straight ray paths through a reconstruction region.
Ideally, I would like to be able to do this for both a rectangular grid region, where each ...
2
votes
1answer
34 views
How can I discover / access various SE (storage elements) in GlideinWMS environment?
I am submitting jobs to Open Science Grid from a glidein-wms enabled submit hosts such as osg-xsede. I'd like to stage some data on SE nearest to osg-xsede submit host, then distribute data to various ...
4
votes
1answer
2k views
Python: Grid with step control ODE solver
I have a problem in physics formulated via an ODE. Now I like to solve it numerically using Pythons scipy.integrate and the therein complex_ode. I figured out how and it works but now I like to ...
1
vote
1answer
290 views
Ray tracer : create an uniform grid [closed]
I wrote a simple ray tracer, and now I try to implement an uniform grid. There is a lot of documentation on how to traverse the grid, but I don't know how to construct the grid.
I have my uniform ...
1
vote
1answer
127 views
How to convert a Matrix to a DistMatrix in Elemental?
I have a Matrix<double> on a single core, the result of doing an MPI_Reduce. I want to do the Cholesky, so I need to ...
0
votes
1answer
51 views
Cells segregation
There is unstructured grid which contains only quadrangles cells. Each cell has 4 neighbors, and known them (has a pointer to them). I can iterate through all cells in the grid. Some cells are marked ...
