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Old 12-11-2019, 07:39 PM   #10 (permalink)
M_a_t_t
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Join Date: Nov 2015
Location: Indiana
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The Van - '95 Chevy Astro Cl
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The new bike - '17 Kawasaki Versys X 300 abs
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The Mercury - '95 Mercury Tracer Trio
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Quote:
Originally Posted by aerohead View Post
Looking at the representation,I don't believe it's worth working with it.In orthogonal view,the model is failing to represent flow separation and vorticity from the square edges which would be present in the real world.I don't have any faith that it could properly represent any aspect of flow.It could lead you down a rabbit hole if you relied on it.
The bumper would be okay if it had adequate corner radii,but as depicted in plan-view,it has none at all,and guaranteed separation.Front fenders Dittoo.A-pillars ditto.
Nothing you can do at the front can solve the issue you have at the back.

The present roofline is too aggressive towards the tail,and will absolutely trigger separation.No where can you exceed 23-degrees downslope.
I understand the diffuser issue,although there's no reason an active diffuser,which could deploy downwards on the highway wouldn't solve the issue.GM did it with their 'Epcot' concept of the early 1980s.
I think you'd be better off just looking at the wind tunnel flow images of real cars here on the Aero Forum.
I'm okay with CFD,just not the 'toy' kind.If you want to get serious,you better bee a millionaire!
I can't find the diagram I remember seeing, but I was hoping to try and get the airflow to be re-directed away from the roof at the windshield and have it come back down and reattach following the roofline. Similar to what seemed to happen with the hood to windshield model (post #3).

Are you eyeballing the slopes or calculating? I have been eyeballing. When I overlay the template (I understand has limitations) the tail pretty closely matches the upper shape. I would like to do some tuft testing, but don't really have the stuff required to record it.




Quote:
Originally Posted by freebeard View Post
Do with this what you will: The Ford 3D Store
Thanks for finding that. They don't have the correct year escort though




Do you think a gurney flap at the tip of the tail would help flow? I remembered I have 2 wide angle dash cams I might be able to use to record from a chase vehicle. I will try to get something this weekend.
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At 55 mph, a 10% drag reduction translates to a 5% increase in fuel economy. At 70mph,a 10% drag reduction translates into a 6% increase -Phil Knox (Aerohead), Aerodynamics Seminar #2
Quote:
Originally Posted by M_a_t_t View Post
My other hobbies have no ROI (making things go fast). So I'm having fun modding my car for better mileage and the side effect is that I save money on gas day to day.

Last edited by M_a_t_t; 12-11-2019 at 08:53 PM..
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