So I tried it! Interesting but a toy really. Below a caveat to anyone using it (I think we'll see more of it in this forum).
Does anyone know any specifics of how the app actually works?
Now as to why you should be very, very, VERY cautious using this Wtunnel-pro tool:
1) It is 2D, obviously. That still should allow it to be good enough for some concept tests like this.
2) From the web page of the tool:What are the units of the simulation ?
There are currently no actual units in the simulation. It was at first designed to be a visual app, not an engineering tool. However, we agree it could be interesting to give some units and values (speed, viscosity, pressure, Reynolds number). We are working on it and might include some units in a future update.
This means that we don't know if the density, viscosity, etc. is equivalent to those of air, water or molten lava.
3) The velocity field is solved in a 120×160 grid on iPad and on a 92×138 grid on iPod/iPhones.
This means that models have to be insanely simple.
4)...we developed a highly optimized simulation engine...
I am not sure how to interpret that, but my first instinct is that they simplified the math. That's never a good idea and the tool does display some really bizarre behavior. Particles stick to the walls and flow separation is moody, but the worse is that the conservation of mass is somehow broken. Simulations like this show it clearly:
The straight lines are velocity field, the dots simulated particles. As one can see, they go into the bottle and keep entering and entering for ever and making a whirlwind), yet nothing comes out. Whatever simplification they did, it was a step too far.
So be very, very, very careful before concluding anything from this tool!
Wind turbines are cool, elegant and magnificent. TANSTAAFL!