Best OSS CFD Package For High School Physics? 105
RobHart writes "I am teaching a 'physics of flight' unit to grade 11 Physics students. Part of the unit will have the students running tests on several aerofoils in a wind tunnel. I also want to expose them to a Computational Fluid Dynamics package which will allow them to contrast experimental results with those produced by the CFD package. There are a number of open source CFDs available (Windows- or Linux-based are both fine), but I don't have much time to evaluate which are the simplest to use in terms of setting up the mesh, initial conditions, etc. — a very important issue as students do not have much time in this unit." Can anyone offer insight about ease of use for programs in this niche?
Re:Too Complicated (Score:3, Interesting)
That's what they used to say about computers.
But when I was learning to write Fortran in school in 9th grade, grad students were learning to write Fortran at the university across town, and making more mistakes and understanding it less than I was.
I would expect the CFD program that would suit this class is something that takes a simple grid input for the surface, simple initial conditions, then runs the flow and plots streamlines or vectors. No need to get into the theory behind the sim computations, just show how things flow across the surface.
If the kids are bright, they'll be ingrained with a desire to figure out (a) more about fluid flow, or (b) how a computer knows how fluid flows, or (c) both.
'Ease of use' relative (Score:4, Interesting)
I've taught computational fluid dynamics and molecular dynamics workshops to university faculty members and can say this: You need to setup the examples for them to play with BEFORE class. There's really no such thing as an easy to use CFD or MD package, especially when looking at what it takes to setup initial conditions. I would strongly recommend that you do a good deal of the leg work, especially for participants that do not have the mathematical background or a background in fluid dynamics, period. It will only help you in the end.
This link [cfd-online.com] will take you to lists of free and free-to-academics CFD codes, but the free ones are really, really bare bones in a lot of cases when it comes to UI. I would not turn high school students loose on these codes without pre-determined examples.
Re:Try XFOIL... leave CFD for later (Score:3, Interesting)
This is the advice you want to follow. Use XFOIL or some other panel method based program to analyze airfoils along side of your wind tunnel stuff.
You can talk about all the things it doesn't do well (boundary layer separation, transonic flow...) and show them some Color Fancy Drawings made by a more advanced simulation as an aside.
Re:Learning vs Exposure (Score:4, Interesting)
Playing around with flow simulations and seeing how changes in geometry affect flow is fun
Agreed, but I'm afraid that playing with CFD will just leave the students frustrated and convinced that physics doesn't work because they can't get CFD to work. I remember kids in high school, (even some in college) deciding that physics doesn't work because they couldn't get newton's laws of motion to match the results they observed experimentally. In reality, they didn't do their math correctly.
If the author want's to quickly demonstrate the principles of fluid mechanics to his/her students here is my plan:
1) Make sure they have a firm grasp on Newton's laws of motion.
2) Have them drop a paperclip and a coffee filter from the same height and measure how long it takes them to hit the floor.
3) Explain to them that this is the effect of aerodynamic drag.
I performed the same experiment in college physics. It's quick and effective.
Re:openFOAM (Score:1, Interesting)
openFOAM is very powerfull, i would say that it's too powerfull for the task
IMHO the minimum requirements to consider even using it are:
-C\C++ knowledge, to be able to write the 'problem statements' you need to be confortable with it.
-Obviously knowledge about fluid mechanics is required: Reynolds/Froude/Mach numbers, Bernoulli equation, steady/unsteady flow. This knowledge is required to be able to pose the problem. You will need a lot of knowledge about PDEs and boundary conditions, and the basics about the finite volume method at least.
-Basic knowledge about Meshing: What is a mesh, what types of meshes there are, what types of meshing algortihms and how do 'computers' mesh stuff. CFD takes a lot of resources, if you want to make a small simple cool movie about a flow meshing right your domain can be the difference between half an hour and half a month of computational time to arrive at the same numerical error.
Dont forget that openFOAM gives you back a LOT of data. You should also know what is it that you want to know (streamlines? path lines? Re/Ma/Fr number plots? vorticity? density? velocity profile? velocity gradient? pressure? pressure gradient? Drag forces? ...)
If you really want to do real CFD go for solidworks or nastran nx (yeah not real CFD but easier), maybe even ADINA or ANSYS (they are overkill but the interface lets you do some simple thing 'relatively' fast). There is also a PDEs Toolbox for Matlab that can do the trick, dont know if there is something similar for SAGE or Octave.
The best option for you i think is to use an inverse airfoil design program for RC Planes. There is one from MIT called Xfoil, and a lot of derivate versions. It let's you do subsonic simulations of airfoils (the geometry for many types of airfoils is already insade either with dimensions or parametrized so you are already saving time). Postprocessing is 'good enough', your students would be able to play with it a bit and see some results. If you are making RC Planes it can show them how starting from a given geometry or parameters, the program runs flow simulations at different attack angles and then 'improves' the airfoil profile iteratively till a certain criterion is met.
Anyways if you find an easy to use CFD program for basic calculations let us know.
Airfoils (Score:2, Interesting)
If you're looking for an airfoil simulator, you might try NASA's FoilSim II [nasa.gov]. "Elementary," student, and undergraduate versions are available, and the non-applet download gives an even more complete version that allows file output. While it's not a full CFD package, it may be good enough for an introduction to airfoil analysis. And while it's not open source, it is free and in the public domain (since it was government produced).
Also, if you're generally looking for open source physics simulations, you should check out Open Source Physics at http://www.compadre.org/osp/ [compadre.org]
In particular, a brief search there yielded the Tracker Air Resistance Model [compadre.org] - a level appropriate simulation that lets students explore the air resistance of falling coffee cups with both viscous (linear) and drag (quadratic) models.
Nearly all of the OSP items have the source code available for modification of the models.
Gerris Flow Solver (Score:1, Interesting)
I recommend gerris flow solver for something that is fairly easy to use.... http://gfs.sourceforge.net/wiki/index.php/Main_Page
30 minutes after building it I had this: http://myrandomnode.dyndns.org:8080/~gmaxwell/theora/hot_xiph.ogv
and I think I spent more time figuring out how to build models in blender. It's not as powerful as openfoam, which is what I normally use now.... but its easier to get started with.
Re:Learning vs Exposure (Score:3, Interesting)
I believe I saw that demonstration in elementary or middle school back in the 1970s or 1980s. In high school, our physics teacher showed a feather falling in a vacuum (much cooler). Get with the '80s already! ;-)