Do you know the difference between the average CFD user and a world-class CFD practitioner? In most cases, it is the ability to generate a grid for complex geometries, which remains a challenge to this day with the tools we have available. Our desire to simulate ever more complex cases has grown faster than the …
Mesh generation in CFD: All you need to know in one article Read More »
There is a big gap between classical RANS turbulence modelling and scale-resolving approaches like LES and DNS, both in terms of computational cost and what can be resolved. As a result, classical RANS modelling may be cheap but not always able to resolve the physics we want to capture, while LES and DNS may be …
Advanced RANS and hybrid RANS/LES turbulence modelling in CFD Read More »
In today’s article, we will be finally looking at the pinnacle of CFD: Reynolds-averaged Navier-Stokes (RANS) turbulence modelling. If you have ever wondered not just what RANS is, but also how it works under the hood, then this article is for you. RANS turbulence modelling is so instrumental that no one can really claim to …
All you need to know about RANS turbulence modelling in one article Read More »
Regardless of whether you are a complete beginner in turbulence modelling and you are hearing the words Large Eddy Simulations (LES) for the first time today, or you are a seasoned CFD expert, I bet you that you have one thing in common: you will have gaps in your knowledge on LES. When you read …
The introduction to Large Eddy Simulations (LES) I wish I had Read More »
CFD is all nice and fun as long as we stay with 2D, laminar flows. As soon as we turn to 3D, turbulent flows, things start to get serious! Turbulence modelling is one of the most fundamental aspects of CFD, and if you want to have any chance of setting up a simulation that accurately models the …
The origin of turbulence and Direct Numerical Simulations (DNS) Read More »
This article will take a deep dive into how to solve the Navier-Stokes equations numerically. We will look at the differences between compressible and incompressible flows and what solution algorithms exist to solve them. Along the way, we will also look at the difference between the conservative and primitive (or non-conservative) variable formulation. We will …
How to solve incompressible and compressible flows in CFD Read More »
In this series thus far, we have looked at the governing equations of CFD, how to discretise them and what their character is. We have looked at different numerical schemes and how they influence various properties, such as accuracy. Eventually, we need to talk about boundary conditions, as every simulation will have to truncate the …
There are probably as many numerical schemes to solve the discretised Navier-Stokes equations as there are stars in the Milky Way. Well, perhaps a few less. Just have a look at OpenFOAM, and you’ll find over 60 discretisation schemes for the non-linear term in the Navier-Stokes equations. And, while that number seems impressive, I am …
Space and time integration schemes for CFD applications Read More »
When setting up a simulation and running it as an unsteady simulation or even just a steady state simulation with pseudo time stepping, we need to decide if we want to use explicit or implicit time stepping. The choice will have consequences down the line, and we need to be aware of them. In this …
Explicit vs. Implicit time integration and the CFL condition Read More »
In our article on how to derive the Navier-Stokes equations from scratch, I showed you how we can derive the governing equations of fluid mechanics. Once we have found an equation that we want to solve, and we do not have an analytic solution available, we have to approximate a solution to that equation, for …