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Questions tagged [simulation]

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

38 questions with no upvoted or accepted answers
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How can Navier--Stokes equations have asymmetric solutions such as Karman vortex streets

The Navier--Stokes equations are axially symmetric, so with symmetric boundary conditions, how can features such as Karman vortex streets develop? I understand that in reality symmetry does never ...
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508 views

How does GAMG in OpenFOAM really work?

I use OpenFOAM for CFD simulations. A very popular preconditioner is GAMG which needs a low number of iterations per a time step in SIMPLE or PISO solvers that are used to simulate the fluid flow. I ...
4
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98 views

Tracking for two meshes

I'm dealing with physical simulation (position based dynamic). Now I'm trying to realize tracking for two meshes. In order to explain what does it mean, let's assume that we have two similar meshes: ...
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0answers
229 views

Sound Waves Simulation in 3D Environment

I want to do a simulation of sound waves including wave propagation, absorption, and reflection in 3D space. I did some research and I found this question in stackoverflow but it talks about ...
4
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0answers
112 views

What are the governing equations solved in coupled atmosphere-ocean models?

In (hydrostatic) atmospheric general circulation models, for example the so-calle Primitive Equations, consisting of the horizontal momentum equation, the hydrostatic balance, the continuity equation, ...
3
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0answers
91 views

Tracking the speed of 2D oscillations on a lattice

I wrote a Monte Carlo simulation of the 2D Lotka-Volterra model on a discrete lattice (with periodic boundary conditions). A video that I produced (which images the system after some number of monte ...
3
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0answers
89 views

Is it normal to expect the error of simulation of a damped harmonic oscillator to decrease as the damping factor decreases?

I am simulating a damped harmonic oscillator using the RK4 method of numerical integration. I am comparing the simulated results with the analytical ones (for the free evolution case) and obtaining ...
3
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0answers
54 views

Discretizing boundary conditions for vortex methods

I am working on a fluid simulation using vortex methods. For this I must compute the vortex sheet on my boundaries given as: $$ \gamma(\mathbf{x}) - \frac{1}{\pi}\int_S \frac{\partial}{\partial\mathbf{...
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230 views

N-body simulation for particles

I would like use N-body simulation for measure a torque on an object in a liquid (helium). It's a 2D study. On the site : http://www.browndeertechnology.com/docs/BDT_OpenCL_Tutorial_NBody-rev3.html I ...
3
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0answers
195 views

How to estimate if a velocity field is statistically homogeneous?

For a 3D velocity field $\mathbf{u}$ obtained by direct numerical simulation. Assuming that the field is defined on a periodic domain $\mathcal{P}$ of periodicity $L_x$ in the $x$ direction, $L_y$ ...
3
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1answer
330 views

General case Kutta condition

I'm working on a 2D inviscid fluid simulation using a "panel method", with Potential being used to enforce the no-through boundary condition. I'm trying to incorporate the Kutta condition, which says ...
2
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0answers
35 views

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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0answers
156 views

Simulation of surface tension-dominated interfaces

I want to simulate the shape of the free surface in a small fuel tank in microgravity, which is very slowly being emptied. The tank is not symmetric, the geometry is given by CAD (e.g. step file). ...
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249 views

Error in MD simulation with Lennard-Jones potential in C, resulting in a lack of conservation of energy

I'm working on a MD simulation using the Lennard-Jones potential and the Velocity Verlet algorithm. The code compiles and runs, but the energy for each time step is not conserved; it decreases ...
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160 views

Initial conditions of nbody problem

Note: I have edited the original question to try to be clearer. I'm trying to simulate a gravitational nbody problem with a Barnes-Hut algorithm, in which the bodies start in a homogeneous sphere ...
2
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0answers
35 views

Limitations of particle in cell method for high density plasma

Are there any limitations of particle in cell (PIC) method for high density plasma? To be more specific, is modeling of a narrow channel of high density plasma possible or are there any limitations ...
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116 views

Algorithms for adding hydrogens on a molecule

I want to add hydrogens to some linear polymer molecules (polyethylenes). I know some working methods like using PyMOL internal function h_add. This method works, but hydrogens are added at distances ...
2
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0answers
78 views

Can similarity criterion help reducing calculations in Finite Element Analysis (FEA) problems?

Can similarity criterion help reducing calculations in Finite Element Analysis (FEA) problems? I'm using NX (a thermal and CFD simulation software) to simulate the temperature and fluid field of a ...
1
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0answers
46 views

Magnetostatic modelling Radia: Increasing distance between magnets a produces positive force until a certain point, beyond which force goes haywire

I have two sets of magnets. One set consists of two electromagnets (Shown below: Blue) and the other set consists of two NdFeB N40 permanent magnets. Both sets of magnets lie on the same plane. I want ...
1
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0answers
59 views

Dealing with simultaneous collisions in N-body sim

I have written an 2d N-body simulation in Python which allows collisions between the bodies. A body is modeled as a circle whose area is proportional to its mass. Each time the sim advances by one ...
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0answers
19 views

Does excitation type matter in a time-domain simulation/computation of a transfer function of an LTI system?

Let's say I am running a FDTD simulation of a wave-equation to determine a transfer function of an LTI system: \begin{equation} H(f) = \dfrac{Y(f)}{X(f)}\ \end{equation} where $Y(f)$ and $X(f)$ are ...
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39 views

Simulating periodic boundary condition with long_range interaction

Consider 2 particles in a 2D plane. There is a long-range interaction between two particles: $$f (r_i-r_j)= \frac{\vec{r_i} - \vec{r_j}}{|r_i-r_j|^3}$$ $$\vec{r_i} =(x_i,y_i)$$ $r_i$ determines the ...
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0answers
282 views

Simulating a Hill-Type muscle model

I'm trying to do biologically based locomotion animation. I have a Hill-Type Muscle Model (see reference 1) that I've implemented in code. I can find the initial lengths of the tendons, then do a ...
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0answers
63 views

Dielectric in an external electric field

I want to numerically solve for electric field of an object in an external electric field. The object has linear displacement field such that its permitivity ($\epsilon$) is constant. The object's ...
1
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0answers
63 views

RCWA for Non-Periodic Structure?

I have a quick question regarding Rigorous Coupled Wave Analysis (RCWA) for numerically solving problems (in optics). I am trying to simulate a device which is non-periodic in x, y directions (but is ...
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0answers
63 views

Solving a nonlinear problem with CDF

I'm trying to solve this problem: $\begin{cases} \partial_t E=-k\left([f(\rho)-i.\left[\delta+\frac{1}{2}a\left[\dfrac{\nabla^2_{\bot}}{4}+1-\rho^2\right]\right]]E - 2CP\right)\\ \partial_t P=-\...
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786 views

BiCopter simulation in Matlab

I derived a bicopter dynamical model with two servos and two BLDC motors. And now am trying to simulate it using Matlab. As base for simulation I used this paper and this code Unfortunately, the ...
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0answers
53 views

Software to simulate behavioral economic models?

I am looking for a way to simulate behavioral economic models to illustrate the effects of changing parameters. I am familiar with statistical analysis (especially R), but I only have few programming ...
1
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0answers
104 views

Conservation at grid interface in adaptive mesh refinement

I am using adaptive mesh refinement to solve one dimensional inviscid Burgers equation. However I am facing some difficulty to handle grid interfaces which are not uniform (coarse-fine grid interface)....
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0answers
40 views

Spectra of the energy flux VS transfer spectra?

In direct numerical simulation of turbulence what is the advantage to look at the spectra of the energy flux rather than the transfer spectra? The transfer spectra corresponds to the triple-velocity ...
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63 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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48 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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53 views

Is there a simple way of implementing dark energy into a n-body simulation?

I'm working on a gravitational n-body simulator and would like to implement dark energy into it but all I can find is papers with relativistic equations which I don't really understand. Is there a ...
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48 views

Determining the pseudo-time period of a system of $n$-pendulums via Kane's method in Python

We can use Kane's method to integrate the equations of motion for a system of $n$ pendulums with arbitrary masses and lengths (see derivation). In particular, if $(x_i,y_i)$ denotes the Cartesian ...
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83 views

References on the topic of DEM and XDEM

DEM: discrete element method. XDEM: extended discrete element method. For my current project of furnace simulation with granular materials, I am interested in the methods mentioned above. I have not ...
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55 views

Energy anomolies in many body simulation

I am trying to simulate the gravitational interaction between many bodies. I am using a direct PP force calculation and a 4th order symplectic integrator with a variable step size. The energy of ...
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1answer
40 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 (...
-1
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1answer
810 views

Any note on Immersed boundary finite difference method?

For parts of a talk, I need a note on "Immersed boundary finite difference method", mainly about the reason of appearing this branch in the finite difference methods, considering mathematical ...