The beginning

The beginning.

In the beginning I should explain CFD abbreviation. So lets just go with it. It is obviously Computational Fluid Dynamics, in other words simulating fluid flow with the use of computer. Nowadays many simulations are done with the use of commercial/academic software. I will deal mostly with ANSYS package (Fluent, CFX). These rich environments let us solve complicated flow problems and can be very helpful as annoying and deceiving at the same time. As aspiring scientist and observer of CFD newbies (I'm still a newbie too), I prepared a list of most common misconceptions and false strategies taken by rookies.

The most common mistakes and misconceptions

1. My geometry has to be 3D and detailed - first sin of rookies is to make 3D domain. Why? Because its cool looking, and basically, you know, objects are 3D in reality (but are they really?). I could name this sin differently as does not look for simplifications. People most often oversee simplifications, like:
- you can use just half (one third, fourth etc. ) of domain, because flow is symmetrical
- you can make it 2D because pressure, velocity aren't changing much in one of directions
- your domain doesn't have to be so big!
-you don't have to add small details that won't make a difference

2.Add too much physics. It's also about simplification. In principle, simulation has to be as close as possible to real thing, But some effects are negligible, like gravity in relatively high speed forced flow (forced means here induced by fan, pump or another device). In many cases it's beneficial to omit some of the forces or phenomena (like phase change) and make it simple first time. If first simulation runs without problem more interactions can be added.

3. Make too dense mesh. I know the more elements, the results are more accurate, but solving one case for two weeks isn't fun. Go from really lousy mesh to gradually finer and see what is the impact on results,

Can you think of more mistake and misconceptions? Let me know.
Umm... This is just a beginning. We'll do something real next time. Uh sorry something simulated.