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Questions tagged [simulations]

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10 views

Numerical simulation of electromagnetism force from random wire

I want to learn numerical simulation and as my first project I would like to simulate electromagnetic field derived from DC flowing in random shaped wire. Are Maxwell equations enough to calculate 3D ...
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1answer
30 views

Potential Flow integration (no-voice and very beginner!)

Let's say I managed to compute a velocity field that is divergence-free. How do I integrate it over time? meaning, I created a potential function, set v to be curl of potential function, so I have now ...
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0answers
11 views

Gauge fixing in Ginzburg-Landau simulation

I am developing a computer simulation of the Ginzburg-Landau model of superconductivity. In a few words, I have discretized the domain with finite differences and I am using Nonlinear Conjugate ...
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0answers
23 views

Interpolation on curvilinear grid [migrated]

How could someone interpolate spatial data on a curvilinear grid, like the one in the picture shown?
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1answer
51 views
+100

Assumptions for 2d simplification of Navier-Stokes flow

There are many cases where Navier-Stokes flow is simplified to a two-dimensional problem to reduce the costs for a numerical simulation, e.g., flow around an airfoil, channel flow or pipe flow. To ...
2
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2answers
84 views

Wave simulation without reflection on the boundaries [duplicate]

I would like to numerically simulate a wave (let's say in a string) with different boundary conditions: Fixed endpoints Periodic Boundless $\varphi(x, t)$ is the value of the wave (vertical ...
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0answers
15 views

Heat transfer in Steady vs Oscillating flow through a Matrix material (Conceptual Input needed)

I have been trying to model heat transfer and pressure drop for oscillatory flows inside a closed channel flowing past a matrix material. My intuition and experimental results (in journal papers) tend ...
1
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1answer
34 views

The actual mass of a particle in coarse-grained molecular dynamics

If I use Lennard-Jones unit with the fix langevin command, and set both the mass and damping parameter as 1, does it mean the actual mass of a particle in this ...
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1answer
43 views

How to deal with constants on computer simulations? [closed]

I'm beggining learning about natural simulations on my courses and I had a few questions about time, and especially with the game "Universe Sandox²". I know about the basic Newton's formulas about ...
2
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0answers
28 views

Geant 4, simulate Tc-99m decay

I have a setup of Monte Carlo simulations in Geant4, and I'm able to simulate radioactive events from isotopes such as I-131 and F-18, which are defined in the RadioactiveDecayData5.2 files. Tc-99m ...
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0answers
38 views

Time units in simulation

I am hoping that someone could give me some insight about my problem. Currently I want to simulate the evolution of a gaussian wavepacket in a time-dependent potential using the Crank-Nicolson scheme. ...
2
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1answer
59 views

Doubt while simulating electric circuits

Today, I was simulating DC electric circuits just for knowledge and fun using PhET interactive simulations. But I'm having trouble understanding these circuits which I made. I think that both these ...
2
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2answers
33 views

How can I determine a planet's mass based only off of information about its orbit and its parent star?

I'm coding a video game with procedurally generated planetary systems and I want some and I want to make sure I'm at least somewhat scientifically correct. I've reached the part in my code where I ...
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0answers
12 views

Determine Field of View from Given Simulation Box Size

I want to determine the field of view as would be seen by a telescope corresponding to a simulation box size(comoving) of, say 100^3 Mpc^3.As I understand the box size for simulation is a rough ...
2
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0answers
19 views

How to set the number of fermions in the whole system in fermionic-DMRG program?

In infinite DMRG (density matrix re-normalization group) algorithm, we increase size of super-block by two sites in each iteration. How do we set number of fermions in the system? Let's say we want to ...
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2answers
47 views

In Wang Landau method, how can I avoid large entropy difference?

Summary: In Wang Landau method, you have to calculate the probability $\exp (- \Delta S)$ but $\Delta S$ is generally large when the size of the system is not small. How can I make $\Delta S$ small? ...
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0answers
70 views

How to deal with fermionic operators in density matrix renormalization group (DMRG)?

Let we have 1D Hubbard model with spinless fermions $$H = -t\sum_i^{L-1} \big(c_i^\dagger c_{i+1}+c_{i+1}^\dagger c_i\big) +V\sum_i^{L-1} n_i n_{i+1}$$ Though this model can be mapped onto XXZ ...
2
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0answers
31 views

Stability criterion for leapfrog in relativistic physics

I am doing a 2D MD simulations of charge carriers in graphene using the Leapfrog algorithm. I am trying to prove that, in some specific cases (when distance between particles is small), the method is ...
2
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1answer
35 views

What is this secondary transition in the simulation of the Ising model?

Here, the horizontal axis is the strength of the ambient magnetic field. The Hamiltonian I used is $$H = -h\sum_i \sigma_i - J\sum_{\langle i \, j \rangle}\sigma_i\sigma_j.$$ The horizontal axis is $h$...
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0answers
61 views

Wolff cluster update in Monte Carlo simulation - at critical temperature [closed]

A general question to the Monte Carlo experts. When I use Wolff algorithm for global updates, say for Ising 2d, I always flip at least one spin (the initial random spin in the cluster). So, near the ...
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0answers
26 views

Is there a mass spectrometer software that can measure the mass of a hydrogen atom [duplicate]

For a school project I need to measure the mass of a hydrogen atom either as a lab experiment or with a computer simulation. Since I don't have the appropriate equipment for the experiment, does ...
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0answers
46 views

Is there a mass spectrometer software that can measure the mass of a proton

I spent a lot of hours looking for mass spectrometer software (or Cathode-ray simulator) that can measure the mass of a proton or any sub atomic particle. Until now I only found software that work on ...
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2answers
318 views

How can one obtain the metric tensor numerically?

I am self-studying General Relativity. Is there a method for obtaining the metric tensor exterior to a specified mass distribution numerically? In the simplest case of a spherical mass this should ...
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0answers
21 views

Resonant frequency of Split Ring Resonator (SRR)

I am working on circular and square split ring resonator design as part of my thesis. I wrote a Matlab code to calculate SRR resonant frequency but I am not getting the same answer of any published ...
0
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1answer
56 views

Screening of a coulomb-like potential

Imagine that we have a potential in the form of: $U(r) \propto \frac{1}{r^n}$ in a 2D system, with the high concentration of particles interacting with the above potential. How do you find the ...
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1answer
45 views

Ising magnetization in metropolis

I am working on the Metropolis-Montercarlo algorithm for the square lattice ising 2D. Im running the simulations for a given lattice size, running from low temperature to high temperature, and ...
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0answers
25 views

Entropy in the Klimontovich Picture of Kinetic Theory

In the Klimontovich picture of kinetic theory, a classical $N$-body system is fully specified by the phase-space distribution $$ \rho(\vec X,t) = \sum_{i=1}^N\delta[\vec X-\vec X_i(t)] , $$ where $\...
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0answers
54 views

Negative Eigenvalues of the Hessian

I am calculating the eigenvalues of the Hessian for a ferromagnetic system. My energy has the zeeman term, a nearest neighbor exchange term, and a dipole-dipole term. I create the hessian where my ...
1
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1answer
59 views

Metropolis Monte Carlo Phase Transition for small systems

Metropolis Monte Carlo simulation for the argon liquid fails to reproduce correctly the pressure-temperature isotherm from the point of liquid-vapour coexistence: Why such a phenomenon appears ? The ...
3
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4answers
146 views

Is it possible to draw a potential landscape for this system?

Attention: The question was modified for numerical solution. (see Update 2) I have the following system of differential equations: \begin{align} \dot x & = -x+F(a\,y+b),\\ \dot y & = -y +F(...
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0answers
69 views

Why does conservation of energy appear to be violated? [closed]

I am currently working on a rigid body simulator. Before getting proper collision and rotations working, I decided to simulate the collision of spheres as axis-aligned objects. The simulation works ...
1
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1answer
107 views

Brownian dynamics simulations in confined geometries [closed]

I am currently trying to implement a 2D Brownian dynamics simulation in confined geometries (corrugated channels, of the form $A\cos(2 \pi x) \ + B\ $ in this case). The concept is to compute the ...
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4answers
168 views

Is there a name for this wave effect?

So I was using this wave simulation (https://phet.colorado.edu/sims/html/wave-on-a-string/latest/wave-on-a-string_en.html) when this happened; using the settings: Oscillator, High tension, no damping. ...
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1answer
58 views

Periodic autocorrelation function for Ising model?

I am trying to calculate the autocorrelation time for a 2-D Ising model Monte Carlo simulation. As the autocorrelation function, I am using $$\chi (t) = \frac{1}{t_{max}-t} \sum_{t' = 0}^{t_{max}-t-1} ...
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2answers
52 views

Multiparticle simulation and Velocity Verlet Algorithm

The Velocity Verlet algorithm requires using an updated particle acceleration to compute and updated velocity. If that acceleration depends on a force that depends on distance to the other particles, ...
2
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1answer
42 views

Solar System Position and Velocity data

I'm trying to create an nbody simulator and to test it I'd like some real world data. A good test would be the solar system. I've come across the JPL Horizons software but if cant seem to figure out ...
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1answer
98 views

Weird results of Monte Carlo simulation

I'm simulating the 3D Ising Model using the Wolff update algorithm. I am using the Mersenne Twister RNG. When the lattice size is $L = 50$, the specific heat curve looks very weird!! I want to ...
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0answers
88 views

Is there an alternative to SIMION?

Is anyone aware of an alternative, possibly open-source, to the SIMION software? From their website: SIMION is a particle optics simulation software primarily used to calculate electric fields ...
0
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1answer
70 views

Implementing a Monte Carlo Simulation for the Gaussian Model

I want to implement a Monte Carlo simulation of the 1D Gaussian Model (the continuous generalisation of the Ising Model). That is the statistical mechanical model with the following Hamiltonian: $$ H ...
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1answer
24 views

Can you use HLvL scheme to solve these quations?

I successfully used HLvL scheme (https://epubs.siam.org/doi/10.1137/1025002) to numerically solve set of equations of this type: $\frac{\partial u}{\partial t} + \frac{\partial f(u)}{\partial x} = 0$...
3
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1answer
141 views

The acceleration of the particles by finite difference [closed]

I would like to approximate the acceleration of a molecular dynamics system. I'm following an online tutorial to solve a set of equations for molecular dynamics. I can use $F=ma$ to calculate the ...
1
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1answer
137 views

Phase transition in a 2D classical Heisenberg model Monte Carlo simulation

I have performed a Monte Carlo simulation of the classical Heisenberg model for a simple 2D square lattice. But I obtain some strange results. In fact, there is clearly a phase transition and a ...
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2answers
78 views

Modeling water flow between two tanks

To familiarize myself with concepts from my system modeling class, I have posed myself the following problem, which I have been struggling with for a good while now. I am an absolute physics beginner, ...
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2answers
44 views

Lateral acceleration to angle [closed]

I am doing a 2D simulation in discrete steps of a vehicle. The vehicle will desire a certain lateral acc. at any given timestep. So I would like to know the delta angle of the velocity vector after ...
1
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1answer
53 views

Why do we need large system in Monte Carlo simulations?

Why do we need to simulate large systems (especially in spin systems)? Is it just a better representation of the real behaviur of magnetic systems? Is there an instability of the finite system with ...
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0answers
32 views

Impurity diffusion from solid to air

I have to put up a simple 1D model to simulate the diffusion of impurities in a bulk material, to a top thin layer made of another material, and compare it to experimental data. I first did it with ...
2
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1answer
38 views

Simulating electrostatics in discrete time steps

I am trying to simulate the motion of several charged particles that are free to move around but have repulsive forces between each other. These may be 10 electrons moving around causing an ...
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1answer
61 views

Analytic and numerical integration of the rocket equation yield different results [closed]

Background The mass of a rocket as a function of time is: $$ m = m_0 - \dot m t$$ Where $m_0 $ is the initial mass of the rocket and $\dot m$ is the mass flow rate. At a certain time all the fuel has ...
1
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1answer
80 views

Why are simulations like Monte Carlo or Metropolis studied for Ising Models when 1d and 2d case have analytical solutions?

I know that absolute analytical solutions exist for the 1d and 2d case but need some intuition as to why these simulation algorithms are used and how do we benefit from them ?
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1answer
68 views

Integrating Carnahan-Starling Pressure

Given the Carnahan-Starling equation of state for a solution of hard-spheres, $$ Z = \frac{P}{\rho k_BT} = \frac{1 + \eta + \eta^2 - \eta^3}{(1-\eta)^3}$$ where $\rho = N/V$ is the number density and ...