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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73 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 ...
282 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 ...
135 views

How does Multi Body Dynamics software work for flexible joints?

I need to model a "fishing rod" in 2 dimensions by joining several "rigid sticks" by flexible/elastic joints. The joints act as plate/torsion springs with different spring constants. The "fishing rod" ...
2k views

Best PARALLEL numerical solver of first order differential equation

I have a system of 256 differential equations that I want to solve numerically. The system represents the Liouville equation, which is a first order, linear differential equation with complex numbers. ...
83 views

$(1+x^M)^{1/M}$ need to be able to calculate any order derivatives vs. $x$ and $M$ for $x\ge 0$ and $M\gt 2$

cannot delete my own question, so I try to overwrite it instead...
506 views

Three body problem in C++

I am in a begginers programming course and we got a little project. I chose to simulate the three body problem using the Euler method. Even though the system is chaotic there are some special cases ...
174 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 ...
81 views

Convergence Criteria for Two Fluid Flow Solver

Which one of the following is suitable for judging convergence in Two-Fluid Flow Solver? 1) Absolute Residual (L^2-Norm). 2) Relative Residual. 3) Fraction Change in Velocity, Pressure and Volume ...
120 views

CFD implementation in software [closed]

I've been learning CFD theory for 4 months (which includes FEA, FDM AND FVM) and now I want to start running simulations. As a novice to CFD software, I would appreciate some advice on where to start, ...
166 views

Methods for solving $x'=Ax+b$ for small, sparse, singular $A$

I am in the process of building a robotics physics engine. I have been using the Linear ODE $x' = Ax + b$ for the core of my physics integration, but have never found a really good solution method for ...
893 views

Simple Simulation Examples in Computational Fluid Dynamics

I would like to incorporate a CFD topic in a project I currently have. The deadline is a little less than a month from now. Basically, what I would like to do is solve some equations and simulate ...
157 views

Is model-view-controller useful pattern useful to build scientific simulation programs?

I work with scientific simulation, but what I like the most in programming is creating graphical user interfaces and 2D or 3D outputs to visualize the evolution of the simulations. I know most input ...
2k views

GPU-enabled Lattice Boltzmann solvers?

Is anybody aware of any GPU-enabled Lattice Boltzmann solvers (preferably on C++/OpenCL and open-source) that would be recommended? I have found Advanced Simulation Library, but it seems to be very ...
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Maximizing unknown noisy function

I'm interested in maximizing a function $f(\mathbf \theta)$, where $\theta \in \mathbb R^p$. The problem is that I don't know the analytic form of the function, or of its derivatives. The only thing ...
2k views

Good desktop PC for molecular dynamics simulations

I want to build a new desktop PC for MD simulations of relatively simple protein/carbohydrate systems using mainly GROMACS and Amber force field. No ab initio or QM-MM simulations are intended for now....
857 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 ...
54 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 ...
115 views

Solve implicit ODE numerically in orbit simulation

I'm trying to plot the orbit of a compact binary star system where general relativistic effects become important. I'm using post-Newtonian approximation and I want to solve the orbit numerically based ...
867 views

How to calculate divergence and vorticity from a velocity field using finite elements

I am in the process of writing a finite element solver for the Navier-Stokes equations and am having trouble computing things like the divergence and vorticity correctly. Currently to compute the ...
649 views

Pressure projection method boundary conditions

When using the pressure projection method to solve the incompressible Navier-Stokes equations do we apply Neumann boundary conditions for pressure only where there are associated no-slip velocity ...
412 views

ANSYS Fluent: Defining External Force on a Cell Zone [closed]

I am using ANSYS Fluent 15 to simulate a case of fluid flow. In my case, I have three cell zones in my simulation, let's call them top, middle and bottom. My requirement is to put a vertical constant ...
116 views

CFD turbulence modelling mean pressures vs peak pressures

I have been experimenting with using Autodesk CFD to investigate facade/ cladding pressures on a (rectangular) building, comparing results with cladding/ facades pressures pressures from design codes ...
119 views

Can other running processes harm the performance of my simulation?

I don't have an high-end machine on which run my simulation (Python + C extensions, based on numpy for calculations) Thus I intend to run the program on my PC, for several hours. I won't use the ...
870 views

Simulating laminar fluid flow in microfluidics device

I just started working in a lab that is trying to design microfluidics devices to trap and manipulate colonies of E. coli cells. Given a 3D model of such a device created in Autodesk Inventor (or a ...
146 views

Relationship between FEM solutions of PDE with different spatial resolutions

I use FEM to simulate deformations of elastic objects for animation applications in computer graphics. The governing equation is generally with the form:  \mathbf{M}\ddot{\mathbf{u}} +\mathbf{C}\dot{...
111 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)....
370 views

How to generate movie of the simulation done in LAMMPS? [closed]

I simulated nanowire deformation using LAMMPS and visualized it using VMD in Centos 6.5. But I'm not able to generate .jpg image file or the simulation movie. How can I proceed??
572 views

Should a colorbar have constant values throughout a simulation?

The default option for matplotlib's pcolormesh (also true for VisIt and I think also true for Matlab) is to allow the maximum and minimum of a colorbar vary. Which ...
669 views

Hypersonic flow in Fluent

I am working in my graduating project about the hypersonic flow, particularly the properties of the air behind a strong shock wave, I try to do a simulation for that process in Fluent but I don't know ...
506 views

PyOpenGL/OpenGL Generating Cosmic NBodys

I am working on a Universe Simulator. I'm stuck on creating the dark matters webs of the universe that look like this: http://www.mpa-garching.mpg.de/galform/data_vis/sim3dnew-highres.png I am ...
454 views

Simulating a Simple Pendulum - Increasing amplitude on each swing?

I am trying to animate a dampened pendulum using RK4 for a highschool project. The equations that describe the dampened system are as follows: (from http://www.maths.tcd.ie/~smurray/Pendulumwriteup....
450 views

Surface charge boundary conditon for Poisson-Boltzmann solver

I want to set up a surface charge boundary condition for the simulation of semiconductor and electrolyte interface. The 2D-Poisson example and surface charge boundary condition are shown in following ...
642 views

How to interpret/convert density in 2D simulations?

Density has units of $kg/m^3$. In simulations often scaling is done to deal with non-dimensional values, so the physical density is converted to the non-dimensional density so that it can be used in ...
2k views

Is CFD used in animations / movies / art?

This is not a technical question, and is asked just out of curiosity. Are computational fluid dynamics (CFD) simulations used in animation movies? (something like shallow water equations, explosion ...
2k views

Finding the correct Molecular Dynamics library

I just started working on some Biophysics research, and I was looking around for a good MD library to use. There is one right now at the university set up in C, with openMC parallelization, but the ...
2k views

What are the differences between CFD simulations and realistic ocean/atmosphere model simulations?

The field of computational fluid dynamics (CFD) is dedicated to solving the Navier-Stokes equations (or some simplification of them). A subset of CFD, ocean and atmospheric models numerically solve ...
92 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 ...
96 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 ...
160 views

Poisson solver diverged

My 2D-Poisson solver is build for simulation of semiconductor. The algorithm is Gauss-Seidel iterative method. If I use simple PN junction for simulation testing, it diverged while I applied high ...
1k views

Boundary conditions in fluid simulation

I'm working on a 2D fluid sim using vortex particles/"vortons" as described in Fluid Simulation for Video Games. Which I think is the same things as the "discrete vortex method". ...
1k views

Using Trilinos and/or Petsc in Windows with Visual Studio?

I am currently working on a project of building a simulator. Up till now I have mostly played around with very simple examples, but with regards to the future I have been thinking that it might be a ...
I'm trying to solve a PDE in Python of the form, $\dfrac{\partial c(\mathbf{x}, t)}{\partial t} = \mathrm{D} \nabla^2 c(\mathbf{x}, t) -\gamma \rho(\mathbf{x}, t) c(\mathbf{x}, t)$ where $c$ ...