Questions tagged [simulation]
Simulation is the process of mimicking the behaviour of a real physical process or system using a representative model.
284
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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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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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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" ...
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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 ...
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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 ...
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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 ...
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Mobile robot path following using model predictive control (MPC)
I'am trying to implement a path following algorithm based on MPC (Model Predictive Control), found in this paper : Path Following Mobile Robot in the Presence of Velocity Constraints
Principle: ...
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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, ...
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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 ...
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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 ...
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Help understanding and implementing fast multipole method for N-body
I've been trying to understand the Fast Multipole Method but not really getting anywhere.
It seems like the fastest mainstream N-body simulation algorithm, and I would like to implement it in an ...
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$(1+x^M)^{1/M}$ 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...
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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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What do C, C++ and Java have that Fortran 2003 don't? [closed]
As you may know, Fortran is widely and longly (?) used in science. I've heard a lot of people saying that we natural scientists should all migrate to C++ or Java. I've seen people increasingly ...
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Is it common or to use objects for calculation of pair interactions in physics and chemistry simulations?
When simulation atoms, molecules, colloids, autc., are there programs that define each interacting unity as an object in the OOP sense?
In my own case, I've been simulating magnetic nanoparticles in ...
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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 ...
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Simple java gravity simulation
I'm trying to write a class that uses Newton's law of Gravitation to work out the field of a planet. I've tested my code by inputting values for Earth, for purely vertical motion, so I should get g = -...
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How to model the mixing of two fluids in a container?
In the context of a research project of mine, I am faced with the difficult task of modeling the mixing of two fluids in a container. I would like to achieve the following:
Given a container (...
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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 ...
3
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Finite difference scheme for 2D sound propagation
I am simulating the sound wave propagation in non-rectangular and asymetric spaces using finite-difference method. I presume linear acoustics equations to be enough (i.e. $\Box p = 0$, $\Box \vec{v} = ...
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2
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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....
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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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0
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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 ...
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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 ...
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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 ...
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Implementing the pressure correction method using finite elements
Ok so I am nearing the completion of my finite element Navier-Stokes solver that uses the $\theta$-method for time stepping and the pressure correction method for the pressure. I am following the ...
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0
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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 ...
3
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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 ...
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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 ...
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1
answer
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How to initiate spirals in this model?
I am trying to reproduce Tang & Othmer paper which is related to excitations and oscillations in G-protein model in Dictyostelium discoideum, an amoeba species. The mathematical model in the paper ...
4
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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 ...
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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{...
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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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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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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??
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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 ...
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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 ...
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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....
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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 ...
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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 ...
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3
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Value of density when there are no or very few neighbours in SPH simulation
I am trying to implement SPH using the directions shown in this paper.
The density needs to be updated using the formula
$$
\rho(\mathbf{x}_i)=\sum_j m_jW_\text{default}(\mathbf{x}_i-\mathbf{x}_j,h)
...
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0
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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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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 ...
2
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1
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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 ...
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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 ...
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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 ...
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Confusion in modeling and computing [closed]
I come from a computer graphics background without any professional in computational science. But I find my job(game engine development) being related to this field. May I ask some general questions ...
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Numerically solve a PDE in Python with a term calculated by coarse-graining
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 $c$ ...
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Simulating interaction of Smart Fluids with Solids
Is it possible to simulate interaction of Smart Fluids with Solids? Is
there a software capable of doing so?
What I Know:
The two software that I know of are Autodesk Simulation Mechanical and ...
6
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1
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Lagrange Multipliers in Multi-body Finite Element Code
I'm working on a Multibody dynamics code using the finite element method to simulate the behaviour of flexible beams (using this paper if anyone is interested/ it is relevant). I'd like to model ...