Questions tagged [simulation]

Simulation is the process of mimicking the behaviour of a real physical process or system using a representative model.

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33 views

Procedure to convert continuous equations of motion to discrete version

Let's take a mobile robot and suppose we know its continuous equations of motion, for example this car-like simple model. Now if I am simulating this robot in a continuous 2D plane, then coding the ...
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49 views

Reproducing a paper's result for Topological Insulators

For the past weeks I have been trying to reproduce Agarwala's results but I've been unsuccessful. From this paper I am trying to reproduce the first and last columns of Fig.2, by implementing eq.2; ...
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In a random walk simulation, how do I get the mean and standard deviation of how many times the walk returns to the origin?

So I'm simulating a 1-dimensional random walk, with 1000 walks that each take 1000 steps. How do I calculate the average number of times that a walker returns to the origin and then the standard ...
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47 views

How to reduce computational time in DDE simulation on Matlab

I need to simulate a network of nodes. The weights of the edges are being given in a matrix . Due to the non-zero distances between the nodes, we consider time-delays, which are computed given the ...
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1answer
166 views

N-body problem with differents solvers (RK2, RK4, Euler symplectic, Stormer-Verlet) : planets drift to infinity

I'm trying to write an integrator for the 2 and 3-body problem. I choose to start from a generalisation to N-body problem so I can just pass my bodies to the same integrator in the two cases. I'm ...
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1answer
220 views

Solving Cahn-Hilliard equation using semi-implicit Fourier spectral methods

So, I have written both a C and python code to solve the 2D Cahn-Hilliard equation: \begin{equation} \frac{\partial c}{\partial t} = \nabla^2\left(c^3 - c - \kappa\nabla^2c\right) \end{equation} ...
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86 views

Large scale nonsymmetric eigenvalue problems in practical applications

I am trying to determine need for solving large scale nonsymmetric eigenvalue problems in both industry and academia. I am interested in any kind of problem where we cannot assume that matrices are ...
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1answer
62 views

Electrostatic Force - Simulate Trajectory of Test Particle using Runge Kutta - Force always Repels

In the center of a 2D-Plane a positive static charge Q is placed with position r_prime. This charge creates a static electrical Field E. Now i want to place a test particle with charge Q and position ...
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75 views

Numerical simulation of magnetic dipole in a inhomogeneous magnetic field

Goal: I want to use Python to illustrate how a magnetic dipole with magnetic moment m2 moves in a non-homogeneous magnetic field in a 2D-Plane. This field is generated by another magnetic dipole with ...
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39 views

How to make a time-parametrization slower around a point but not too slow?

For animation purposes (see below) I need to use a parametrization which 'slows down' near a specific value; More precisely, I am looking for a 'nice' monotonically increasing function $r:[0,1] \to [...
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43 views

Finite element analysis software for acoustic and electrostatic

I need to do a simulation for my thesis project involving some piezoelectric nanoparticles in a fluid beamed with ultrasounds. I'm looking for a software for such simulation and for now it seems me ...
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236 views

Projectile Motion Simulation with Aerodynamics using Euler's Method

I'm trying to simulate the motion of a projectile taking into account aerodynamic drag. The code works perfectly if the aerodynamic drag is zero. However, if the drag coefficient or velocity is too ...
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1answer
36 views

Numerical stability of taking the `mean` of outputs from the simulation of a discrete stochastic dynamical system

I am writing a simulation for a discrete stochastic dynamical system. Since the simulation is stochastic, I need to run the simulation multiple times and then average the values of each timestep. I ...
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55 views

Why is perfect sampling not used in large-scale lattice model simulations?

The statistical physics literature is replete with papers describing simulations of lattice models, such as the Ising model. Typically, these are done through Monte Carlo methods, such as the ...
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1answer
141 views

Conserve energy by message passing?

There are $N$ particles with positions $x_i(t)$ and velocities $v_i(t)$ and mass 1. There is a potential function $U_{i,j}(x_i, x_j)$ between each pair of particles, which is $0$ unless the particles ...
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88 views

Choosing an appropriate time step for a discrete & continuous dynamics simulation

I have inherited of a flight dynamics simulation in C++ which represents a small drone with it's autopilot, actuator dynamics and a solid state IMU. Hence, it is composed of a few models, some ...
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40 views

Effect of Peclet number on concentration profiles

I have been performing convection-diffusion transport studies on microfluidic channels like the following I came across an article that illustrates the effect fo Peclet number on concentration ...
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55 views

computing time scale and steady state concentration in microfluidic channels

I have been performing convection-diffusion transport studies on microfluidic channels like the following The inlet concentration is specific and I obtain the time-dependent concentration profiles of ...
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58 views

Problems with simulation of a spatial filter 4f setup (Python)

I have a question about my code which computes numerically the output field of a 4f setup with a pinhole in the middle which works as a spatial filter. My setup consists of two lenses with 50mm focal ...
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1answer
97 views

Extracting data from VTK simulations using C++

I have been given a few numerical simulations regarding fluid mixing and have been asked to extract a few parameters from them using C++. Altogether there are about 1000 VTK files per simulation, and ...
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1answer
90 views

Is the Immersed Boundary (IB) method a Direct Numerical Simulation?

Is the Immersed Boundary (IB) method considered a Direct Numerical Simulation? A DNS code is the most detailed type of simulation and the most accurate but computationally expensive, right? What makes ...
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34 views

Numerical simulation for a bounded process. Is slight deviation a “normal” fact?

Suppose I have to numerically simulate a process $\{y_t\}$ such that $y_t\geq0$ $\forall t\in\mathbb{N}$, with $t$ denoting time-step. Let's suppose I use MonteCarlo with $\mathscr{N}$ simulation ...
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Discretization formula for a system of two differential equations. “Solution to one of these is the initial condition of the other”. In which sense?

Consider the following stochastic differential equation \begin{equation} dy=\left(A-\left(A+B\right)y\right)dt+C\sqrt{y\left(1-y\right)}dW\tag{1} \end{equation} where $A$, $B$ and $C$ are parameters ...
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1answer
356 views

Reading VTK file into C++ for analysis

I apologize in advance if this post is at all ignorant or elementary, I am a pure mathematician who is newly getting into the world of scientific computing. For my research, my advisor would like me ...
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1answer
107 views

Artificial Intelligence, Modeling and Simulation

Artificial Intelligence (AI) and its subsets i.e. Deep Learning (DL), Machine Learning (ML) etc. are becoming more and more ubiquitous in engineering, technology and science. Modeling and Simulation (...
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272 views

What kind of a researcher am I?

So far, I've worked a bit in modeling, simulations and simple lab experiments, and I've really enjoyed all three research methods to approach a single research question. I can write tricky (in terms ...
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1answer
131 views

How to visualize the vorticity / flow for a rigid body moving through a fluid?

How can I write down two-dimensional Navier-Stokes equations for a simple rigid object immersed in a flow and freely falling due to gravity? I'm trying to view the vorticity that's induced by the ...
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31 views

Tackling multiscale problem in numerical simulation

In a dusty plasma system there are more than one component with different masses, i.e, electrons, ions,neutrals and dust grains. Accordingly, there are more than one temporal and spatial scales ...
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58 views

Spectral solver on em-pic

I'm recently studying for the spectral solver to implement EM-PIC code. I read an article and have some questions. Many PIC codes uses spectral solver to overcome numerical artifacts on FDTD. In the ...
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1answer
106 views

How to get free energy surface of a 3d Ising Spin system using Monte Carlo simulation?

I am doing a Monte Carlo Simulation of the properties of a 3D Ising Spin system. I want to get the free energy surface of the spin system from the simulation. It is a magnetization vs free energy ...
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58 views

Stress during unloading in FEM simulation of an elasto-plastic truss element

I am simulating the behaviour of a single bar composed of two node points by fixing one point and applying a force on the oder node with $F_x = 1$ and fixing $u_y=0$. I am assuming the material to ...
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36 views

Decoupling of the fluid viscosity and incompressibility constraint in a partitioned scheme

I am new here and this is my very first question: I hope I respect all the criteria and rules. I am just getting started with partitioned approaches for solving FSI problems. I am interested in a ...
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2answers
302 views

What are the alternatives for ABAQUS in generating an *.inp file from a CAD model

ABAQUS gives a .inp file (in pre-processing stage) where the information with regard to the preprocessed model is defined, information such as geometry, mesh type, number of elements, boundary ...
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2answers
268 views

How to simulate over 1 billion particles?

I want to simulate human erythrocytes in capillaries. I calculated, that for a 1 meter long and 1 mm in diameter capillary there are about 3 billion blood cells. Erythrocytes are actually discs, but ...
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1answer
146 views

Can one publish a new model and simulation without physical experiments?

When I read strong papers from, say, the Journal of Fluid Mechanics, a simple model, simulations and physical experimental results are given, showing good agreement. Can one publish a new model and ...
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1answer
1k views

Conserving Energy in Physics Simulation with imperfect Numerical Solver

I am creating a C++ Physics Simulation where I need to move an rigid body through an acting force field. Problem: simulation does not conserve energy. Quesiton: abstractly, how is conservation of ...
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59 views

Processing time steps in chunks with Fortran [closed]

My PDE simulation program written in Fortran has to make about 2 million variable time steps. But with each time step it slows down more and more, so that if it initially makes 1000 time steps per ...
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27 views

How to simulate a PDF using data samples like this?

I know two methods to simulate a PDF from random data samples using MATLAB : 1) Using a histogram where I use this command histogram(data,'Normalization','pdf'), it gives PDF like bins. 2) Another ...
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37 views

How to avoid density getting “deleted” in two way rigid body coupling with LBM CFD?

I've been reading this paper recently, which talks about using Lattice Boltzmann methods and two way coupling. Specifically, it outlines fluid solid coupling, and solid fluid coupling, and how simply ...
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Is a complete bacteria simulation with an exascale supercomputer possible?

Will it be possible to simulate a complete (at least simple) bacteria atom by atom on an exascale supercomputer? or is it possible already today with the largest systems? Here, I've read that ...
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73 views

Using MATLAB to simulate the Ising Model

I am using MATLAB to simulate a 1D Ising Chain. I am running into an issue where when trying to find heat capacity, my system has a tremendous amount of noise. I'll post my code and an image of the ...
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73 views

Smoothed Particle Hydrodynamics: Weird clustering of particles. Is that normal?

I implemented a rather simple SPH simulation using a cubic-spline-kernel and a simple non-iterative pressure solver as described in this PDF in equation 9. I followed algorithm 1 of that paper (...
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534 views

What guidelines should I follow for simulation software projects?

I am not sure whether this question belongs here, but I would like to give it a try and benefit from the experience of the people at scicomp.SE. From my experience, the software quality in ...
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1answer
118 views

Computing autocorrelations of configurations in Monte Carlo simulations

In the context of Monte Carlo simulations, I am trying to learn how I should ensure that the configurations of my system are not correlated for the chosen interval of measurements. I have found out ...
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1answer
126 views

Why don't we call the simulation “a model for …”?

When a set of model equations, e.g. some coupled differential equations, has solutions that behave in ways similar to real-life phenomena such as blood flow in the heart, a wave movement, or a plate ...
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1answer
138 views

Calculating the Convolution Using DFT (FFT)

I have the following convolution as part of a numerical simulation. $$T(r)=\int \mathrm{d}^3r_2\, p(r_2)f(r_2)\alpha(r-r_2)\, .$$ My problem is that the analytical expressions for $f$ and $p$ do ...
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72 views

How one can simulate a system given by differential equation?

I want to simulate a diffusion environment given by the differential equation $$\frac{\partial u(x,y,t)}{\partial t}=D\left(\frac{\partial^2 u(x,y,t)}{\partial x^2}+\frac{\partial^2 u(x,y,t)}{\...
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What is the best methodology for physics simulators of large floating base rigid body systems?

I want to implement a physics simulator for large floating base rigid body systems from scratch. The Rigid Body Dynamics Systems (RBD) should typically have the following characteristics: About ~50 ...
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49 views

Simulate friction arround steady-state point

When simulating a friction dynamic system, I have come to a problem when approaching steady-state. In the example below, a box moves along a surface with a certain friction coefficient: ...
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1answer
113 views

Plasma Simulation Software Advice?

I’m looking for software that can simulate “hot” plasmas of multiple ion species...so some sort of simulation software that could calculate ion temperature and density distributions taking into ...

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