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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Simulating a dataset from model output when model includes multiple binary deviation-coded variables

I am trying to simulate data using parameters from a glmer() model output. The model, which comes from a published paper, is as follows: DV ~ 1 + group* sex *verb type + trial number + (1 |participant)...
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Softening vs Smoothing Length... Is There a Difference?

I have a simple questions on terminology. Is there a difference between softening length and smoothing length? I have been using the 2 terms interchangeably as the minimum distance between particles ...
dcro's user avatar
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Why does a two-body simulation result in no change of the y-component?

I've been attempting to create a model of a heliocentric orbit based on Newton's law of gravitation: $$ \frac{d^2 \vec r}{dt^2} = -\frac{GM}{|r|^2} \hat r $$ This is what I have so far: ...
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Calculating Madelung constant via Ewald summation

I am attempting to calculate the Madelung constant for NaCl using an Ewald sum derived by Nijboer. There are other methods and published codes to do this, but I am specifically interested in working ...
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Starting configuration for Molecular Dynamics

I have to build a bilayer using a structure obtained in a previous MD simulation. In the structure, some chains of the molecules cross the simulation box as shown below. I added water layers to the ...
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In electromagnetic simulation, how much does the feed model impact an antenna's directivity performance and E-field phase readings?

Question: How much would a simplified feed model in an EM simulation alter an antenna's directivity and the E-field phase reading when compared to using a more complicated/realistic feed model? I am ...
Xingda Chen's user avatar
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Modeling Homeostatic Regulation with Python: How to Simulate Dynamic Systems

Hello Computational Science community, I am working on modeling a dynamic system that involves homeostatic regulation in Python and I could use some guidance on how to implement it. Here's a brief ...
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Damping not working in Verlet simulation with absolute constraint

I'm trying to build a simple physic simulation with Verlet intergration, which I'm currently implementing as such: ...
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Deformation matrix, Math hack for stability on large simulation steps?

So there is a numeric technique for updating a deformation gradient in MPM that goes as: $$F_{n+1} = (I + \nabla \vec v \Delta t)F_n$$ This works for small time steps but for large time steps ...
Makogan's user avatar
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Improved euler on hybrid methods where both time and space are discretized?

I am trying to understand how to use the improved euler method on MPM simulations. In the kind of MPM simulation I am doing with forward euler the order of operations is as follows: Write particle ...
Makogan's user avatar
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Verlet integration on grids or how to get better stability in hyperelastic simulation

I am using MLS-MPM to simulate both solid and fluids. It works, but the amount of time steps I must do for hyperelastic solids is absurd. To give you some perspective, I am able to simulate just the ...
Makogan's user avatar
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Professional orbital simulation software methods, accuracy, runtime

I'm working on an orbital body simulation as a personal project. I understand that it's not going to be as good as professional software, but I'm wondering what contemporary, general purpose, ...
Indrada's user avatar
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How can we simulate two different module both magnetic field and cathodic protection in comsol?

I need to simulate magnetic field of corrosion in my project. How can we simulate two different module both magnetic field and cathodic protection in comsol.
mary's user avatar
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How to calculate the change in water level height after each step in a water displacement simulation?

I'm trying to write a very simple simulation of volume/water displacement. Every timestep a sphere gets lowered a bit further into a cylindrical container filled with water. While the physics behind ...
Johann Gruber's user avatar
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Monte Carlo simulation of classical Heisenberg model doesn't represent Curie curve

I've created a JavaScript file to execute and log average energy and magnetization values of 2D lattice classical Heisenberg model. I run the simulation with parameters, ...
M. Çağlar TUFAN's user avatar
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I encountered some issues simulating the shape transition of silicon clusters using LAMMPS

== I have been trying to write an input file for lammps to simulate the shape transition of a nanoparticle of silicon using multiple potentials to obtain the best structure, which I will compare with ...
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MPM course, implicit updat clarifification

In the 2016 SIGGRAPH notes on MPM the authors explain how to do an implicit update in section 11.4 throguh by this formula: It is not clear to me what the $j$ is over in this case (for eq 202), is it ...
Makogan's user avatar
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Energy potential involvign pressure and viscoscity?

Making a really long explanation short. I am looking for an energy density function for an incompressible isotropic fluid that involves both viscoscity and pressure. The reason is, there is a way to ...
Makogan's user avatar
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Solving a minimization problem without flattening inputs?

I am reading this paper on improving time steps for solving simulation problems: https://www.math.ucla.edu/~jteran/papers/GSSJT15.pdf The authors developed this energy function: $$E(x) = \frac{1}{2\...
Makogan's user avatar
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1 answer
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Projection (or fractional-step) methods Vs coupled method for incompressible Navier-Stokes

My question is in the context of the finite element method. Incompressible Navier-Stokes equations can be solved using the coupled method or projection/fractional step methods. Each method has its ...
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Poisson equation solution in a semiconductor structure

I am trying to solve the $\textbf{1-D}$ Poisson equation for a semiconductor structure at equilibrium (There is no external bias applied). $\textbf{Background}$ \begin{equation} \frac{d^2V}{dx^2} = -\...
Photon's user avatar
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Is FDTD A Method for Simulating Quantum Field Theory for Photons?

I have been reading a bit about Quantum Field Theory and Photons, I read that the equation(s) for spin 1 massless particles (photons) in Quantum Field Theory are just Maxwell's Equations described in ...
cgbsu's user avatar
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2D wave equation is numerically unstable using Finite Difference Method

I'm working with simulating both the heat and wave equation in 2D in a Python code. When simulating the heat equation, I learned about the CFL which I used to get a numerical stable solution. I found ...
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Normalisation in tensor networks

I am trying to implement the iTEBD algorithm for the $PXP$ model, i.e, the hamiltonian is $$H = \sum_iP_{i-1}X_iP_{i+1}.$$ Here $P$ is the projector onto the ground state and $X$ is the usual pauli x ...
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Geant4, simulate photon emitted into lead

I have just learned Geant4 and recently I tried to simulate photons emitted into lead. After I collected the data and figured out the transmission of photons. I found my data is bigger than the ...
SHZ's user avatar
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1 answer
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How to correct for collision in $N$-dimensional bounded motion of a particle?

I want to numerically simulate the motion of a point particle (unit mass) in $N$-dimensional space according to the force $f(\vec{x}, t)$ and bounded by a set of linear constraints (equalities as well ...
haoyu's user avatar
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3 answers
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What evidence exists to suggest that computational science produces more information than studying real phenomena as they are?

What evidence exists to suggest that computational science produces more information than studying real phenomena as they are? I think about this topic often, because I think synthetic knowledge is a ...
mavavilj's user avatar
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4 votes
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How to do a parametric study of arbitrary 2D surface?

I need to do a parametric study of the performance of a room heater on different rooms by simulating the temperature distribution in there. The problem here is that the rooms are not simple rectangles ...
Ken Grimes's user avatar
2 votes
1 answer
226 views

Using velocity verlet algorithm for nbody simulation results in planet leaving orbit

I'm new to computational physics and attempting an n-Body simulator in java but for some reason the planet in orbit leaves the orbit when it reaches the fastest accelaration aka the closest point to ...
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Simulate Jump-Diffusion $dX_t = \mu(X_t)dt + \sigma(X_t)dW(t) + \int_{\{|c| <1 \}}g(X_t,c)\tilde{N}(dt,dc) + \int_{\{|c| \ge 1 \}}h(X_t,c)N(dt,dc)$

I would like to be able to model an SDE having the form $$dX_t = \mu(X_t)dt + \sigma(X_t)dW(t) + \int_{\{|c| <1 \}}g(X_t,c)\tilde{N}(dt,dc) + \int_{\{|c| \ge 1 \}}h(X_t,c)N(dt,dc).$$ where $W$ is a ...
oliverjones's user avatar
4 votes
3 answers
512 views

Why not use the convolution theorem for explicit timestepping?

Consider the advection equation \begin{equation} \frac{\partial C}{\partial t} + u\frac{\partial C}{\partial x} + v\frac{\partial C}{\partial y} = 0 \end{equation} I want to do a forward time, center ...
nalzok's user avatar
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2 votes
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Beam propogation method for a waveguide. How to get single mode?

I am simulating a waveguide using diffractio python library (https://diffractio.readthedocs.io/en/latest/readme.html). The idea is to create a single mode waveguide using wave propogation method. ...
wosker4yan's user avatar
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How to implement large rotations in total lagrangian formulation (nonlinear FEM)?

I have developed an Octave script to solve the nonlinear Euler-Bernoulli beam equations with linearized von Karman-strains, i.e. higher-order terms are dropped. The simulation results agree with ...
Tepa's user avatar
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Can I build an electrostatic simulation of conductive objects using just the method of images?

I wish to build a simulation of self-assembling wires. Think lots of ball bearings in a 20KV electric field and they form emergent structures. If I use the method of images to figure out what the ...
Mandrake_The_Magician's user avatar
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Is a 2021 MacBook Air sufficient for modeling and simulations research in fluid dynamics?

I code mostly in Matlab, simulating various simple fluid dynamics models. One particular simulation has the potential to become sort of complex, though I believe the set of coupled equations will ...
user42169's user avatar
3 votes
1 answer
1k views

Solving Kepler's Equation with Newton-Raphson Method

Note (2022/03/07): This question is solved. Unfortunately, I'm not able to accept the correct answer by Lutz Lehmann, because I screwed up my registration and the account which posted this question is ...
kruemelkeksfan's user avatar
0 votes
1 answer
72 views

What's the relationship of machine learning and mechanical simulation?

What's the relationship of machine learning and mechanical simulation? Particularly, machine learning is about learning from a large sample and predicting based on filters tuned on that. Mechanical ...
mavavilj's user avatar
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Feasibility of synthetic, simulated predictions w/o matching against empirical physical measurement?

Feasibility of synthetic, simulated predictions w/o matching against empirical physical measurement? This has puzzled me lately. So, while it's sometimes common to approach modelling and model ...
mavavilj's user avatar
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4 votes
0 answers
105 views

Any literature that extensively discusses the ability to strongly inter-/extrapolate computationally on little empirical data?

Any literature that extensively discusses the ability to strongly inter-/extrapolate computationally on little empirical data? This topic has fascinated me, but I find that it seems a bit novel. ...
mavavilj's user avatar
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3 votes
2 answers
117 views

How are consistency constraints maintained in Circuit Simulation?

I have always taken for granted circuit simulators and I didn't spend time understanding now. I wish to understand better now. Normally when you forward simulate ODE systems there is a single dynamic ...
FourierFlux's user avatar
6 votes
0 answers
305 views

FEM : energy minimization VS PDE solving

Engineering FEM When I studied engineering, I learned the traditional approach for finite elements for elasticity. The point was to solve the PDE $-div(\sigma)=f$ as: Multiply your PDE with a test ...
Txnda's user avatar
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3 votes
1 answer
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Type of computer used for computation

In some scientific papers I see that authors provide what type of simulation tool and what type of computer was used for computation. For example: The computations were performed using MATLAB in ...
Lee's user avatar
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4 votes
0 answers
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Identifying an unknown P.D.E. from solution data

I have a black-box simulation that produces the time evolution of a probability density function p(x, t) in 1 dimension from arbitrary initial conditions p(x, 0). The underlying simulation occurs on a ...
beables's user avatar
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-1 votes
1 answer
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Can someone help or point me out to C++ source code for a two body orbit simulation using symplectic integration?

I've professional experience with physics simulations and C++ programming, although I don't have specific experience with astrophysics simulations. I'm trying to build a two-body evolving system ...
Simo's user avatar
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1 vote
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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 ...
user_1_1_1's user avatar
1 vote
0 answers
55 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; ...
Victor RM's user avatar
-1 votes
1 answer
365 views

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 ...
Applesauce44's user avatar
-1 votes
1 answer
59 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 ...
Alex Kps Bdc's user avatar
2 votes
1 answer
1k 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 ...
Mathieu Rousseau's user avatar
2 votes
1 answer
479 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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