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2
votes
1answer
43 views

Meaning of $\nabla_{\mathbf{p}_k} W(\mathbf p, h)$ in PBF

I'm reading this paper on Position Based Fluids and I couldn't understand the meaning of $\nabla_{\mathbf{p}_k} W(\mathbf{ p_i - p_j}, h)$ in the equation 7 (see below). …the gradient of the ...
2
votes
1answer
46 views

Magnetic force and torque for 2D neodymium ball simulator

I'm trying to write a simulator for neoballs. I'm doing only 2D for a start, in which each ball has a magnetic moment, m, that is in the x-y plane. The simulator will use time-step integration at 60 ...
1
vote
0answers
12 views

Total energy in tight binding methods

How to calculate total energy in tight binding methods? The total energy is calculated as the sum of the eigenvalues of the occupied state?
0
votes
1answer
31 views

Transition between raytracing and physical(wave) optics

In the past I have done raytracing simulations for large things, and physical optics (FEM, FDTD) for small wavelength-scale things. Now I have a very large lens that focuses down on a waveguide. I ...
0
votes
1answer
17 views

DPD weight function

I was wondering about the connection between the weight function of the random force and the conservative force between DPD particles in a standard DPD simulation. Both usually have the form [Groot ...
0
votes
1answer
17 views

Ising simulation-dimensionless

My question is about dimensions in Ising model.When we want to simulate Ising we use dimensionless parameter as you know.We choose J to be 1 and also K equal 1 and when temperature is 2.26 then it's ...
3
votes
2answers
565 views

System that is more efficient to simulate than to compute

I know some physics calculations require alot of computing to solve. Are there currently systems where it is more logical to do an experiment to "let the universe simulate the experiment for us" and ...
1
vote
1answer
51 views

Orbiting in space

Background I'm making a game where a spaceship needs to orbit another object in space at a set distance. Space is, unlike other game, like space is in reality. Friction less. (at least to my ...
1
vote
0answers
37 views

Simulating a noisy image: Poisson Noise Clarification

I'm currently working to simulate an image that mirrors the output of a CMOS camera we have in the lab. My images include Poisson (photon) noise as well as a gaussian (readout) noise. My issue is ...
0
votes
0answers
23 views

Diffusion Equation for Particle Hopping with drift

First of all, I haven't studied partial differential equations yet, hence this question might sound silly. I am doing a simulation for particle hopping on a lattice with python. I was said that in ...
1
vote
1answer
36 views

Initial velocity of particles in a 2D gravity simulation

In N-body simulations of protostellar clouds (or similar objects), each particle is has a set of characteristics: mass, size, position, velocity, and (if the object is large enough or if we want to be ...
2
votes
0answers
31 views

Is there a form of rigid body dynamics that uses unit quaternions instead of Euler angles?

I’d like to know specifically about an elegant way of deriving a second derivative of an orientation quaternion from a torque and a moment of inertia matrix, if one is available. The straight forward,...
5
votes
2answers
144 views

Black hole simulation

NASA published a computer generated black hole image. In the image you can clearly see the event horizon and the light of background stars graduating from "smeared" to normal. However, between the ...
0
votes
0answers
25 views

Air pressure equalisation

I'm programming a physics simulation and have the air pressure impact the movement of rigid bodies in the system. I know how to (approximately, both for simplicity and performance) specify bodies' ...
0
votes
0answers
19 views

2D slab model for LJ potential

I have a program implementing a LJ(Lennard-Jones) molecular Dynamics(MD) simulation with isokinetic thermostat. I want to modify that program to study the phase characteristics of LJ particlesin 2D ...
1
vote
2answers
72 views

Which timestep should I use for a $N$-body simulation of the Solar system?

I am trying to implement a $N$-body simulation of the Solar system and I am stuck on the issue of the simulation timestep size. At first I would like to use a simple Euler stepping scheme. Knowing ...
3
votes
1answer
61 views

Collision between a “spring” and a particle

I am currently attempting to create a simple 2D physics engine, and I just need to know how to solve a certain collision. I have particles, and between any two particles, springs can be connected. ...
4
votes
0answers
45 views

Barycenter correction for inner planets in solar system?

I want to run simulations of the solar system, and I've read in some papers that to speed up the simulations it is useful to use the barycenter correction of the inner planets (from Mercury to Mars), ...
6
votes
2answers
184 views

How do we explain the existence of liquids, from a mathematical or computational perspective? [closed]

This post asks why matter exists in three phases. Most of its answers explain the existence of liquids with some variant of the following: liquids happen when thermodynamic conditions, temperature ...
1
vote
2answers
51 views

Calculate gravity between two points

I am trying to build a simulation of gravity in LibGDX using Bullet physics. To simplify it, I just want to apply a force on some body towered a (0,0,0) point. I got my body mass and it's location ...
2
votes
0answers
41 views

What is the meaning of the Fourier Transform of the electric field of a well guided mode in a dielectric waveguide?

I have been studying waveguiding in dielectrics for a while now; however, I cannot understand the meaning of the Fourier transformed electric field. I will first give some background information. ...
0
votes
0answers
43 views

What would be the long-term effects of stopping the Sun?

TL;DR: In an orbital simulation, what are the effects of pinning the major body to the origin, and how could these effects, if any, be mitigated? Consider an orbital motion simulator; your basic n-...
1
vote
2answers
77 views

Model/formula for bouncing ball

I'm programming an animation of a bouncing ball, and I want it to be as realistic as possible. I fully understand the physics while the ball is rising and falling: It accelerates downward at 9.8 ...
5
votes
1answer
41 views

Identify binary stars in nbody simulation

I'm doing a nbody simulation, and I'm interested in the formation of binary systems in the temporal evolution. I can identify them by eye, but I don't know an algoritmic criteria that can say me if ...
-3
votes
1answer
75 views

Need motion equations for falling ball for simulating [closed]

I am currently M.S student in artificial intelligence(A.I) and working on my thesis on reinforcement learning, which robot should learn by itself how to control a quadcopter. Long story short, I have ...
0
votes
1answer
45 views

Notation of a vector containing equation in a paper

I'm trying to implement Coulomb long range interactions into a molecular simulation program using a particle-particle/particle-mesh Ewald solver. The following equation from the paper "How to mesh up ...
0
votes
0answers
25 views

Two axis non linear Inverted Pendulum

I am Electronic Engineering student. Sorry for my english, I am very rusted. I am modeling the inverted pendulum for a Class Project and I wondering if any could answer one question. In this web ...
0
votes
0answers
29 views

Keplerian orbits and radial velocities: problem with true anomalies

I am writing a pure Python code to calculate radial velocities of stars with massive objects orbiting them. I am following the formalism from Murray & Correia (2011) (hereafter MC11). In a given ...
4
votes
1answer
23 views

How would I find the velocity of an object after it doesn't fully enter the gravitational pull of a planet and is kind sling shot out of its gravity?

Obviously that question doesn't have a lot of jargon having to do with math and physics. I am not a physicist, I'm not a mathematician, I'm trying to make a game and simulate some physics found in ...
0
votes
0answers
19 views

2-D Ising model temperature of equilibrium [duplicate]

I have simulated 2-D Ising model in C#, but my scatter plot for magnetization versus temperature is an decreasing line (you know that the correct plot decreases quickly in a temperature near 2.3). I'...
0
votes
0answers
28 views

Why is more difficult for a DFT to converge with non-periodic conditions?

I am simulating a cubic amorphous silica system. When all boundaries are periodic the SCF iteration converges rapidly. However, when the boundary is not periodic in the $x$ direction, the SCF ...
1
vote
0answers
62 views

How do I model the motion of a particle changing acceleration vector (2D)?

I want to model a particle with an arbitrary initial velocity, and estimate the time it takes to reach a final point given a constant magnitude of acceleration. It should take the quickest path to the ...
2
votes
0answers
20 views

Derivation of generation of time between two subsequent particle enters into computational domain

I have problem with understanding derivation of one equation in following problem. You have 1D computational domain (it is not 1D but because it is symmetrical and we are watching only radial ...
0
votes
0answers
13 views

Parameters for modelling 4 level 2 electron gain medium for laser

I have an EM simulator that can model laser gain medium by a 4 level 2 electron system. However the model requires pumping wavelength, lasing wavelength, pumping linewidth, lasing linewidth, decay ...
0
votes
0answers
61 views

use FEMM to simulate electric field for a magnet inside a coil

I'm trying to simulate a magnet inside of a coil of wire, with and without current running through the wire. I'm using the free FEMM software to try to simulate this, but I don't think i'm setting ...
4
votes
1answer
75 views

Can I re-wind gravity?

Suppose I perform an arbitrary simulation where I integrate the motions of a collection of particles which interact only gravitationally. Suppose I use a time reversible integrator (to be specific, ...
4
votes
1answer
70 views

How to conserve momentum when numerically-integrating the path of a charged particle through a magnetic field

I have the python script attached below, which is intended to track the trajectory of a charged particle in a static, uniform magnetic field. It is very simple to calculate the instantaneous force ...
0
votes
0answers
12 views

Why does SCF convergence on DFT worsens for a parallelepiped domain?

I am currently simulating parallelepiped domains of amorphous polyethylene with DFT. I would like to know the reason why the convergence of SCF worsens when the domain is not cubic. Does the k-point ...
0
votes
1answer
46 views

How to simulate an accelerometer in code

I want to write a simulation of an accelerometer (with a fixed X and Y axis in this case but with respect to a world coordinate frame) on a stick, rotating in a circle around a fixed point. From that ...
3
votes
2answers
67 views

Does inelastic collision say the ball bounces back to you when thrown at an angle on ground?

I created a bounce simulation using exactly the formula from Wikipedia. The behavior I observe is not what I would expect in two cases: When two balls hit off-centre, they act the same as if the ...
5
votes
1answer
68 views

Methods for handling close approaches in $N$-body simulations

In direct gravitational $N$-body simulations, what are the preferred methods for handling close approaches between bodies in order to preserve the accuracy of the evolution of the system?
0
votes
0answers
40 views

How to calculate the forces that create precessing motion of a spinning top?

I'm trying to create a a spinning top simulation, and I have a problem with simulating the precession. I read the Wiki article about precession, which have the formula for angular velocity of ...
1
vote
0answers
75 views

Simulating TE011 mode in cylindrical cavity, Comsol [closed]

I have been trying to simulate TE011 mode in a cylindrical cavity by modifying the example given in Comsol site(https://www.comsol.co.in/model/computing-q-factors-and-resonant-frequencies-of-cavity-...
0
votes
1answer
36 views

Calculating true anomaly of a hyperbolic trajectory from time

I'm creating a simulation for orbiting bodies with my primary challenge being calculating the true anomaly of a trajectory with respect to time. I have figured out circular, elliptical, and parabolic ...
1
vote
1answer
57 views

Model of a heating system in an industrial hall

I want to model a heating system in an industrial hall. The system consists of: a heating plant, a pump, 2 pipes (each pipe is 500meters long) and a machine tool. The required heat for the machine-...
0
votes
0answers
20 views

How to find positions in the equilibrium state of mass-spring system?

I've simulated 3D mass-spring system (mesh/network). First the system was in equilibrium state of it own (called state {A}). If I moved some of the masses in the system to the new positions, the ...
1
vote
1answer
54 views

Force of Gravity of a stationary object acting on another object moving through space

Story: I have x and y positions of a spaceship as it moves through space to some goal location at [1000, 700]. A record of its movement is given by: ...
0
votes
1answer
66 views

Cavity resonator modelling and simulation of em fields inside the cavity

I want to model a cylindrical cavity resonator and study the different modes of em fields inside it using MATLAB/COMSOL. Please refer me books/articles or other resources so that I can achieve my goal....
0
votes
1answer
82 views

Newtonian Gravity Simulator?

Could anyone suggest me a good (and possibly free) Newtonian Gravity Simulator software available on the web, where it might be possible to simulate the Solar System dynamics and playing with it, by ...
0
votes
1answer
32 views

Setting up initial conditions of parabolic orbits, centre of mass frame

I am writing a simulation of 2 bodies in coplanar parabolic orbits in their centre of mass frame (in C++) and am having difficulties setting up the initial conditions for the velocities. The total ...