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Questions tagged [fluid-dynamics]

The study of the properties of fluids and gases in motion

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5
votes
1answer
748 views

Finite-difference discretization for a convective term

How does one discretize the classical convective term in a transport equation using finite differences? I know the finite volume schemes out ther i.e. upwind, central differencing etc. Are there ...
13
votes
4answers
326 views

How to create a random 3D domain representing a plant's root structure?

I would like to model laminar flow of water from roots to the stem of a plant. At the very end of the roots, the tubes vary from millimeter to centimeter scale in diameter and length. As we get closer ...
3
votes
2answers
423 views

What numerical methods are recommendable for simulating two phase immiscible fluid flow through a pipe with high capillary pressure?

I'm simulating two phase immiscible drainage (air displacing water) in a rectangular domain of size .6mm x 2.4mm (2 dimensions) using Ansys FLUENT software. I am using an implicit Volume of Fluid ...
10
votes
1answer
253 views

Why do we have to rerun the CFD solver for higher Reynolds number?

I started to learn OpenFOAM from the Cavity tutorial which is provided at the web-site. When experimenting with different Reynolds numbers, in section "2.1.8.2 Running the code", tutorial says to ...
4
votes
0answers
286 views

How does one handle the source term in the Shallow Water Equations when using the discontinuous galerkin method? [closed]

I use the discontinuous galerkin method to solve the steady flow 1D shallow water equations with a bump at the bottom. This flow is frictionless. I use the runge-kutta method to approximate the time ...
3
votes
2answers
1k views

Looking for a library or algorithms to perfom clipping 3D unstructured meshes by a set of surfaces

We have a 3D (volume) unstructured, possibly hybrid, degenerative irregular mesh data structure that we are capable of generating (mostly composed of hexahedra and general polyhedra, using a mix of ...
12
votes
3answers
2k views

finite volume method: unstructured mesh vs octree adaptation + cell cutting

I'm working with the OpenFOAM C++ Computational Continuum Mechanics library (it can deal with fluid-solid interaction, MHD flows...) which uses arbitrary unstructured meshes. This was driven by the ...
17
votes
5answers
2k views

Is there a good, easy-to-use, high quality open source CFD solver out there?

My thesis is on developing numerical methods for model reduction in combustion. I run my methods purely on the chemistry part of combustion simulations, and I have plenty of case studies for 0-D ...
6
votes
1answer
510 views

Benchmarking performance in CFD: how to compare machines and codes?

Informally in our lab, we have developed 2 metrics to compare CFD solvers over the range of machines we have access to. One is called COMP, which stands for COde Machine Performance. This single ...
5
votes
2answers
149 views

Which tool/metric do you recommend to evaluate the quality and validity of a Large Eddy Simulation?

The idea behind Large Eddy Simulation is to solve explicitely the scales of the flow that are resolved by the computational grid and to model the sub-grid scales. Ideally, the cut-off between these ...
9
votes
1answer
1k views

What is the most accurate interpolation method for a 3D-flowfield on a structured grid?

I solve multi-species, compressible Navier-Stokes equations on a 3D structured grid. I have obtained a solution on a given grid (let's say a relatively coarse one). I want now to refine my grid and ...
18
votes
4answers
556 views

Which methods can ensure that physical quantities remain positive throughout a PDE simulation?

Physical quantities like pressure, density, energy, temperature, and concentration should always be positive, but numerical methods sometimes compute negative values during the solution process. This ...
12
votes
1answer
400 views

What spatial discretizations work for incompressible flow with anisotropic boundary meshes?

High Reynolds number flows produce very thin boundary layers. If wall resolution is used in Large Eddy Simulation, the aspect ratio may be on the order of $10^6$. Many methods become unstable in this ...
30
votes
4answers
2k views

Why is local conservation important when solving PDEs?

Engineers often insist on using locally conservative methods such as finite volume, conservative finite difference, or discontinuous Galerkin methods for solving PDEs. What can go wrong when using a ...
23
votes
4answers
1k views

When is a high order method useful for computational fluid dynamics simulations?

Many numerical approaches to CFD can be extended to arbitrarily high order (for instance, discontinuous Galerkin methods, WENO methods, spectral differencing, etc.). How should I choose an ...