# Questions tagged [fluid-dynamics]

The study of the properties of fluids and gases in motion

473 questions
Filter by
Sorted by
Tagged with
64 views

39 views

### Simulating flow in a branched pipe

I am trying to simulate 1D advection and convection of a solute in the following blood vessel segment. I would like to know if this system can be simulated in COMSOL or MATLAB. I have used pdepe ...
178 views

### Implications of thermodynamic inconsistency in CFD calculations

During my PhD work, I had to use tabulated values of thermodynamic properties of gases in some Computational Fluid Dynamics (CFD in short) simulations. My tables are discretized in temperature and ...
56 views

### What is appropriate boundary condition for Poisson pressure equation?

I'm doing CFD simulations in unstructured grids. Well, it's a bit different from conventional unstructured grids that are used mainly in FEM or FVM as tetrahedral meshes. Mine is a voxelized mesh of ...
26 views

### What is Voronoi particle tracking?

I've been trying to track this down, but google is giving paywall papers that don't appear to be directly related to computational science, or simply don't explain the source algorithm. There's an ...
83 views

### Are there any commercial CFD codes that implement a Discontinuous Galerkin scheme?

I've been reading about the Discontinuous Galerkin discretization scheme and it's application to CFD for fluid flow. It seems to be a promising method for simulating turbulent flows, by using higher-...
42 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 (...
24 views

### How to ensure values stay within range?

e.g. water in a height map Choosing a range with a margin of error for typical model behaviour seems practical. Could we instead (1). predict maximum values; or (2). have a natural maximum? 1. ...
160 views

### Lattice Boltzmann methods vs Navier stokes/ other eulerian methods for *water* simulation

Note, there is already a question here, however the answers don't answer the original question, let alone specific considerations when dealing with nearly in-compressible fluids (water). Another ...
51 views

### Should the derivative of an array be calculated array by array or element by element in CFD codes?

I am making my own finite difference computational magnetohydrodynamic code in Fortran 90. Looking at other codes they appear to calculate for example their $x$-derivatives, bb of their variables, e.g....
22 views

### Riemann solvers for metastable phases

Most Riemann solvers I've come across can solve the Riemann problem only under certain conditions such as convexity of the equation of state. But what happens if the fluid enters a metastable state or ...
93 views

### How to compute turbulent energy cascade

I need to compute the kinetic energy cascade using a finite volume solution in an equally spaced grid. I wonder if it is more correct to first compute the kinetic energy in the space (or time) domain, ...
46 views

### Confusion about Zabusky and Kruskal's stepper for the KdV equation

In Zabusky and Kruskal's paper about solitons, they derive the following update for the Korteweg de Vries equation (their footnote 6): \begin{align*} u_{i}^{j+1} = u_{i}^{j-1} - \frac{1}{3} \frac{k}{...
47 views

### Understanding MP-PIC implementation in OpenFOAM

The multiphase particle-in-cell (MP-PIC) method is characterized by mapping particle properties from the Lagrangian coordinates to the Eulerian grid. However, the implementation of this method in ...
25 views

42 views

I have developed a python code for a lid-drive cavity model. However, my results are not converging. The algorithm of my code looks like this: Euler Momentum Equation looks like this: $$\frac{u^{n+1}... 1answer 59 views ### What is the exponential trick to include laplacian term in Rayleigh-Bernard simulation I have come across a Rayleigh-Bernard simulation code which doesn't have the laplacian term but an integrating factor (in the exponential form) containing viscosity and diffusivity. I found out that ... 0answers 56 views ### Solving a simple Shallow Water model Hi. I have a question at Mathematics and they suggested post here, once it's not common. I transcript as following. Many thanks I need to solve with basic methods this simple Shallow Water Model: ... 0answers 36 views ### Is semi-Lagrangian 1D advection identical to upwind Euler, when |u|<\Delta x/\Delta t? This looked true to me, I worked through the algebra for 1D and confirmed it. But no one seems to mention it, so maybe I'm missing something... I'm using Bridson's SIGGRAPH 2007 course notes. [5MB ... 0answers 120 views ### What are some good debugging habits for numerical simulation? I'm currently writing a lid drive cavity CFD code on python. Currently, my code has some issues (values jumping bear b.c). I was wondering what are some good habits in debugging numerical codes. ... 0answers 8 views ### Universal formulation of adiabatic equations of state in compresible finite-volume simultions I code some finite element solver which should work for broad variety of materials (i.e. gas, liquid, solid, plasma) and large span of compressions resp. densities. I want to simulate things like ... 1answer 148 views ### What will be the impact of quantum computing on existing numerical techniques (e.g. CFD)? Quantum computing seems to be a very active and promising development area in computer science. However, I am curious as to what impact (if any) quantum computing will have on existing classical ... 0answers 47 views ### WENO scheme on curvilinear coordinates I've been developing a curvilinear FVM code. So far I've implemented the PPM scheme and am looking into adding WENO schemes. So far I've been discretizing the grid metrics using a second-order central.... 0answers 61 views ### OpenFOAM and CFDEM on GPU I have a simulation project written for OpenFOAM and CFDEM and would like to find an alternative to run it on GPU since raising the number of cores already provided a promising speed up and ... 1answer 57 views ### How to get started with numerically solving a Stochastic Navier Stokes equation I originally posted the question on the math stackexchange, and was told I should try here. I’m researching Stochastic PDE, in particular the Navier Stokes Equation, and would like to estimate the ... 0answers 31 views ### Dealing with spurious oscillations in particle tracking methods I work on modelling high intensity discharge xenon-filled lamps. The model governing the discharge is quite complex and sadly includes fluid dynamics. After some time, I managed to implement a finite-... 0answers 11 views ### Compute cell values and isosurface constant from density values of particles I am trying to reconstruct the surface for a fluid simulation based on a list of particles using the Marching Cubes algorithm. From different resources, such as http://paulbourke.net/geometry/... 2answers 153 views ### Automatic timestep adjustment in a CFD solver I have developed my own 3D Finite Volume Navier-Stokes solver based on projection method for nonuniform grid. I am looking to incorporate automatic timestep adjustment at each time step based on ... 1answer 67 views ### Is “Gradient Computation” in Finite Volume Discretization Really 2nd order accurate? Based on this, pp 245, we go through these steps to discretize a gradient statement, namely \nabla\phi: 1- Gauss theorem reads,$$ \int_V\nabla \phi dV = \oint_{\partial V}\phi dS $$2- Integral ... 0answers 84 views ### Double mach reflection at a inclined wedge I am running into a strange problem when solving the 2D compressible Euler equations on a inclined wedge. To elaborate, my top boundary condition seems to emitting some type of instability. I have ... 1answer 56 views ### Simulating magnetic particles in a field free point generated by two opposing magnets This is probably a long shot with such a short time, but I've been trying to get theoretical data for a project I'm working on. The project involves using a very simplified version of magnetic ... 0answers 42 views ### Instability in Lattice Boltzmann Solver I wrote a Lattice Boltzmann Solver in Rust a little while back using both the BGK approximation and the TRT (two relaxation time) method on the D2Q9 lattice. In both cases I run into major stability ... 1answer 79 views ### Imposition of Dirichlet BC for Fourier pseudospectral in this paper I was trying to implement the algorithm from the paper "Adapting a Fourier pseudospectral method to Dirichlet boundary conditions for Rayleigh–Benard convection". I am having a hard time to ... 0answers 31 views ### 3D Tollmien-Schlichting Waves Imposed in a Channel Flow (Are Physics correct?, etc) So I am trying to do some further tests on a 2nd-order code Incompressible Navier Stokes equations, by studying transition to turbulence in a Poiseuille flow. Specifically, I'm interested to see ... 1answer 139 views ### Finite Element - Flux Calculation I am solving an advection-diffusion equation using the FEM and am having trouble calculating my fluxes. I start with the equation,$$\frac{\partial n}{\partial t} = \frac{\partial j_{n}}{\partial x}\...
Problem. Consider the one-dimensional adjoint Euler equations for $(x,t) \in \Omega \times [0,T]$ with $\Omega \subset \mathbb{R}$ and $T > 0$  \varphi_t + \Big(\frac{\mathrm{d}F}{\mathrm{d} U}(x)...