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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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 ...
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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,
...
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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 ...
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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 ...
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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:
$$E(x) = \frac{1}{2\...
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Projection (or fractional-step) methods Vs coupled method for incompressible Navier-Stokes
My question is in the context of the finite element method.
Incompressible Navier-Stokes equations can be solved using the coupled method or projection/fractional step methods. Each method has its ...
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Poisson equation solution in a semiconductor structure
I am trying to solve the $\textbf{1-D}$ Poisson equation for a semiconductor structure at equilibrium (There is no external bias applied).
$\textbf{Background}$
\begin{equation}
\frac{d^2V}{dx^2} = -\...
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Is FDTD A Method for Simulating Quantum Field Theory for Photons?
I have been reading a bit about Quantum Field Theory and Photons, I read that the equation(s) for spin 1 massless particles (photons) in Quantum Field Theory are just Maxwell's Equations described in ...
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2D wave equation is numerically unstable using Finite Difference Method
I'm working with simulating both the heat and wave equation in 2D in a Python code. When simulating the heat equation, I learned about the CFL which I used to get a numerical stable solution.
I found ...
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Normalisation in tensor networks
I am trying to implement the iTEBD algorithm for the $PXP$ model, i.e, the hamiltonian is
$$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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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.
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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.
...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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