wannabeclean
11-24-2006, 09:02 PM
Hi.
I did this 'tuft' test on my car a while back and decided to post the results here for those that find it interesting (or amusing)
Before the days of multi-million dollar wind tunnels and CFD software, this was the 'old-school' way of finding high drag areas in a cars design. Hundreds of pieces of yarn are taped to the car and when driven at speed, show the areas of high drag.
The yarn flutters back and forth and twirls around in areas where the airflow is disrupted.
Smooth airflow shows up as yarn that sticks to the body of the car and has very little movement. Stagnant areas in the airflow show up as just that - the yarn just sits there.
Why did I do it ..... uh ....... boredom ???
http://www.geocities.com/swbin73/PICT377i.jpg
http://www.geocities.com/swbin73/PICT3809.jpg
http://www.geocities.com/swbin73/PICT3806.jpg
http://www.geocities.com/swbin73/PICT3832.jpg
http://www.geocities.com/swbin73/PICT3836.JPG
In the above image, you can see the 'cowl induction' effect that is formed at the edge of the hood line. The yarn is actually sucked into the area. You might also notice in the previous image, how that the airflows around the side of the car - up and over the drivers side window vs. straight back. (This was partly due to the fact that I had the mirror folded back at the time)
http://www.geocities.com/swbin73/colorized.jpg
What I found out by viewing the video, is that certain areas that I thought would behave a certain way actually did quite the opposite. In the image above, the blue areas were areas where that there was little to no movement in the yarn (the air was stagnant)
Areas in green were areas that had a vacuum to them - and pulled the yarn inwards much like the area around the windshield wipers.
Brown areas were areas where there was the most turbulence. The yarn spiralled in these areas.
I did this 'tuft' test on my car a while back and decided to post the results here for those that find it interesting (or amusing)
Before the days of multi-million dollar wind tunnels and CFD software, this was the 'old-school' way of finding high drag areas in a cars design. Hundreds of pieces of yarn are taped to the car and when driven at speed, show the areas of high drag.
The yarn flutters back and forth and twirls around in areas where the airflow is disrupted.
Smooth airflow shows up as yarn that sticks to the body of the car and has very little movement. Stagnant areas in the airflow show up as just that - the yarn just sits there.
Why did I do it ..... uh ....... boredom ???
http://www.geocities.com/swbin73/PICT377i.jpg
http://www.geocities.com/swbin73/PICT3809.jpg
http://www.geocities.com/swbin73/PICT3806.jpg
http://www.geocities.com/swbin73/PICT3832.jpg
http://www.geocities.com/swbin73/PICT3836.JPG
In the above image, you can see the 'cowl induction' effect that is formed at the edge of the hood line. The yarn is actually sucked into the area. You might also notice in the previous image, how that the airflows around the side of the car - up and over the drivers side window vs. straight back. (This was partly due to the fact that I had the mirror folded back at the time)
http://www.geocities.com/swbin73/colorized.jpg
What I found out by viewing the video, is that certain areas that I thought would behave a certain way actually did quite the opposite. In the image above, the blue areas were areas where that there was little to no movement in the yarn (the air was stagnant)
Areas in green were areas that had a vacuum to them - and pulled the yarn inwards much like the area around the windshield wipers.
Brown areas were areas where there was the most turbulence. The yarn spiralled in these areas.