Aerodynamics testing in OpenFoam
 

Hey everyone,

I'm currently working on a car concept (side hobby project). With this specific concept I was hoping to explore the use of a large boat tail for improved aerodynamics. However with the boat tail I am exploring a number of alternate design variations that I have no idea on the aerodynamic properties. (one less odd variation attached)

To test my design I was hoping to use OpenFoam. I have the .stl files ready, it is just a matter of placing it in the OpenFoam simulation of a windtunnel for results (preferably a diagram of the airflow and pressure that I can view in Blender).

Would anyone have any suggestions on what documentation i can follow (or what preset that I can download)?

Any information would be appreciated.

Regards,
Daniel

concept
 

Daniel,I will have to defer to the others which have experience with CFD,as I have never done it,probably won't.
I think that some if not all that are in use,deal only with 2-dimensional inviscid flow about the centerline of the structure and cannot accurately predict the 3-D wake.
Your rendering ( very nice ! ) looks almost like a trike.If it is a three-wheeler,the CFD programs may not work.( about now I'm hoping someone more knowledgeable is tracking this and will correct if necessary ).
Looking at your image,I would suspect that the entire darkly-shaded area behind the lowest character line will be in separation.It might re-attach,can't figure it without a top view.

Diverging flow is the most sensitive to instability and with the short-tail outrigger front fenders I don't believe the flow will be clean enough behind them to allow attached flow beyond that arcing body crease.
Boat-tails won't work if the onset flow coming at them isn't perfect.One really has to on their toes with respect to them.You just can't cheat.
I'll shut up and make room for the whiz kids.
She looks like a fun project,best to you!

Thanks for your reply
 

Thanks for your thourough reply Aerohead.

I've been jumping into aerodynamics with a brief understanding of the effect of boat tails without really knowing the basics. It is always good to get good advice to help me produce a solid concept.

Will post final design here when done.

Thanks again,
Daniel

I'm giving OpenFOAM an initial look myself, but this appears 3D: youtube.com/watch?v=-ETHwNoR0xI

3D
 

I don't know how to interpret what the images presented in the program.
The 1st tractor image almost looks like a depiction of the bow-wake,but not really the airflow.
The 2nd,side image depicts aft-body dynamics,but one cannot discern if it is only the centerline.It it were 3D it would be impossible to discern.Also,a real wake extends for hundreds of feet behind a vehicle and the program casts no light on this.
If we're bound and determined to bake cookies with arsenic,then I guess we'll always be able to justify the costs to research the complimentary antidote.
I'm with Hucho.There already exists all the empirical evidence we'll ever need to design for low drag.
To me,CFD provides a great public distraction,while the arsonist designers running the fire departments,continue to spray gasoline on the flames.

F--- I- I give up
 

Twice I've tried to respond to this thread.Nothing gets through.I'm done with it.