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Discussion Starter #21
Another 2d-cutplot same as the previous, except that it is located at the vent. Notice
the upward air ruining the air near the spoiler.

 

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Wow, SP!!!

This is really killer. We finally have some relatively conclusive results... thank you so much for doing this.

But seriously, you still should help get me started in this so I can mess with it some more on my own. I'll e-mail you as soon as I get the chance... hopefully I can get my hands on a copy of solidworks for the summer.
 

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By the way, I would think that FloWorks would have some tool to integrate the pressure over the total body area to find a net pressure force... do you know of any way to do that? Or even just for a localized area like the spoiler or underbody?

Man, with the information we have now we should be able to find both coefficients of drag and lift... I gotta figure out how to do this!!
 

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Great work. Very interesting.

It seems that it might be of benefit to fight against the small flow of air that naturally comes out by pushing in with cool air. Less air total that if you fan air out of the lid, but the cooling affect for an IC might see. It would be interesting to see someone with a fan pushing out monitor intake temps. Then reverse polarity of the fan to pull air into the lid and see if that is better.

Also, it seems that those Tom's scoops that everyone has always said don't do anything might actually help quite a bit at cooling the compartment. I would think that the high velocity air going into them would be a much higher pressure than the rest of the bay, allowing it in.

The wing only affects CD a small amount, so no surprise there that it does not do much in your analysis. But when you model a higher wing it will be intersting to see how high it needs to be to have a decent affect. It is usually stated that roof line height is required to get much use out of them.

Thanks for all the work that was put into this.
 

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Discussion Starter #26
Ok, I modified the engine bay a little bit and also added an engine and
transmission. This picture is a sectioned view at the centerline of the vehicle -
with a drivers side engine lid fan pushing down and the passenger side vent
open. Not much has changed from previous analyses. This time I have also
calculated the drag and lift forces and coefficients. They are as follows:

  • Drag Force: 161.4 lbF
  • Lift Force: 101.6 lbF
  • Coefficient of Drag: .332
  • Coefficient of Lift: .058
 

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Also you are neglecting the side air vent into the engine compartment. Wouldn't this change the flow characteristics coming out of the engine lid?
 

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no, the side fan is oly used to suck air in while at a stop light. the door mirrors actually reall kill any clean boundary layer in that area of the car. Removing the mirrors and adding smaller more aero mirrors will make a huge difference.
Those mirrors effect everything from the front tire back at high speeds
 

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Discussion Starter #36
Bill can you elaborate on how you want the front end to look? Do you want me to model it like your airdam?
 

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Discussion Starter #38
Ok, I made some interesting changes. I put a floor, or road surface, in and
specified it as a moving floor that moves at the same velocity as the air. This is
more realistic to what actually happens with a car on the road, and it made a
huge difference to the numbers. I added mirrors this time, opened up the area
on the bottom of the front cutout, and added a front lip.

drag: 216
lift: -69
cd: .44
cl: -.040


 
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