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Old 12-11-2019, 01:09 PM   #7 (permalink)
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Originally Posted by freebeard View Post
It appears you have a 3D shape that's being analyzed in a single plane. Do you have an isometric view? The single plane reduces the computation needed. How long does it take to generate a single view?

Further into the Wind Tunnel and Smoke thread:
Permalink #817[/URL]

IIRC aerohead found a blister on the hood had no appreciable effect on his T-100 pickup.
Its not technically an isometric because of the angle, but there is a different view in the google doc.

a single view in the CFD is fairly quick. less than a minute for the 2d plane. About 45 seconds for the 3d and then time to settle down I guess.

The reason I am avoiding a 3d evaluation is because my model is lacking. I created it based on pictures of the car (from a distance zoomed in), but I don't have one from above to get the taper of the tail and such. I can post one if you think it would provide more information.

I wanted to test the hood to windshield because the air appeared to be separating at the back of the roof. I was hoping that it would indirectly keep flow more attached at the back by changing how it transitioned from the front roofline.

Current car @ 25 m/s

After letting it sit and run it changed to this:

The red box is where the flow lines are originating from.

Originally Posted by aerohead View Post
I have low confidence in all desktop CFD simulations.Optimization of shape involves details which can only be evaluated in 3-D,in ground contact,at 'full-scale,' above critical Reynolds number,on software we can't afford,running on a supercomputer we also can't afford.
From your model,the nose is okay.The nose slope would be at saturation )no additional steeper angle would affect drag),and the windshield angle would also be near saturation.So far so good!
The aft-body ought to follow the 'template.'The last portion of your roof-line cannot support attached flow. The diffuser angle should be relaxed down to 2.8-4.0 degrees otherwise the flow won't follow that either.
The VW XL1 would be a good example to follow.It's dead-nuts on as far as shape goes.
Do you mean the addition to the car or the stock bumper as modeled in my last post?

At the very end where it takes a sharp turn or where the roof ends and meets the tail?

I had to compromise on the bottom of the car.

Do you think the CFD can be used as a data point? Not necessarily accurate for numbers, but just the flow pattern around the car.
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1973 Fiat 124 Special
1975 Honda Civic CVCC 4spd
1981 Kawasaki KZ750E
1981 Kawasaki KZ650 CSR
1983 Kawasaki KZ1100-A3
1986 Nissan 300zx Turbo 5 spd
1995 Chevy Astro RWD
1995 Mercury Tracer
2004 Chevy Astro AWD
2017 Kawasaki VersysX 300

Last edited by M_a_t_t; 12-11-2019 at 01:34 PM..
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