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RobertSmalls · 09-07-2010, 09:33 PM

Jim Bullis,

What's the full title and author of [Morelli 1983]? I'd like to see if my local university has a copy.

While searching for it, I did come across the title of this paper: Automobile aerodynamic drag on the road compared with wind tunnel tests (Book, 1981) [WorldCat.org]

Which is a reminder that unless your wind tunnel / CFD simulation is incredibly complex with rolling road, rotating wheels, air passing through the vehicle, flexible vehicle bodies, crosswinds, and weather, there will be differences between simulations and real world results. How close your simulation can get is a function of your budget. In any case, I'd expect a dozen good simulations to cost FAR less than one failed prototype.

My own efforts at low-budget CFD have been unfruitful. I've used COSMOS FloWorks to generate airflow visualization, but it's really not up to the job of estimating Cd. I've also tried ANSYS FLUENT, which is said to be one of the easiest CFD packages around. Maybe, but I couldn't get the mesher to import my models correctly. OpenFOAM is free, but you'd better have a little programming and engineering background before you use it.

Have you talked to any engineering consultants who specialize in CFD?

I think the concept of operating outside of ground effects is interesting, and a tandem Aptera would be really cool. I wouldn't dismiss solar car style vehicles out of hand. There might be some way to package a human in comfort and safety in a very thin body.

09-07-2010, 09:33 PM	#71 (permalink)
RobertSmalls Left Lane Ecodriver Join Date: Aug 2008 Location: Buffalo, NY, USA Posts: 2,257 Prius C - '12 Toyota Prius C Thanks: 79 Thanked 287 Times in 200 Posts	Jim Bullis, What's the full title and author of [Morelli 1983]? I'd like to see if my local university has a copy. While searching for it, I did come across the title of this paper: Automobile aerodynamic drag on the road compared with wind tunnel tests (Book, 1981) [WorldCat.org] Which is a reminder that unless your wind tunnel / CFD simulation is incredibly complex with rolling road, rotating wheels, air passing through the vehicle, flexible vehicle bodies, crosswinds, and weather, there will be differences between simulations and real world results. How close your simulation can get is a function of your budget. In any case, I'd expect a dozen good simulations to cost FAR less than one failed prototype. My own efforts at low-budget CFD have been unfruitful. I've used COSMOS FloWorks to generate airflow visualization, but it's really not up to the job of estimating Cd. I've also tried ANSYS FLUENT, which is said to be one of the easiest CFD packages around. Maybe, but I couldn't get the mesher to import my models correctly. OpenFOAM is free, but you'd better have a little programming and engineering background before you use it. Have you talked to any engineering consultants who specialize in CFD? I think the concept of operating outside of ground effects is interesting, and a tandem Aptera would be really cool. I wouldn't dismiss solar car style vehicles out of hand. There might be some way to package a human in comfort and safety in a very thin body.