Low drag mirrors

[cfeng]

i use a water tunnel in my lab. i've been thinking about this. with a properly designed rear wing on the hatchback, it may be possible to increase fuel economy.



the top picture is similar to a stock yaris, air swirls in vortex patterns, which means that not only does the yaris need to propel itself forward, but spend considerable energy into moving air. with the correct rear wing, there could be less separation in flow at end and less movement in the air, similar to the bottom picture. i found this picture online, the second picture is misleading because it represents an ideal case with virtually no separation in flow.

the antennae will disturb how the eddies are shed, reducing wasteful swirling of air (reduce a little). similarly, if a wing is designed to reduce the size and number of eddies from forming by increasing turbulence at the rear of the car, the car will have less drag and overall better efficiency.

[Yaristeve]

Originally Posted by cfeng

i use a water tunnel in my lab. i've been thinking about this. with a properly designed rear wing on the hatchback, it may be possible to increase fuel economy.



the top picture is similar to a stock yaris, air swirls in vortex patterns, which means that not only does the yaris need to propel itself forward, but spend considerable energy into moving air. with the correct rear wing, there could be less separation in flow at end and less movement in the air, similar to the bottom picture. i found this picture online, the second picture is misleading because it represents an ideal case with virtually no separation in flow.

the antennae will disturb how the eddies are shed, reducing wasteful swirling of air (reduce a little). similarly, if a wing is designed to reduce the size and number of eddies from forming by increasing turbulence at the rear of the car, the car will have less drag and overall better efficiency.

Intersting drawings. What do you think (as in "do you think they work?") of those little "shark fin" vortex generators and Air Tabs? I was thinking of sticking on a row of the latter on the top of my hatch door but not on the sides as they recommend.

[cfeng]

Originally Posted by Yaristeve

What do you think (as in "do you think they work?") of those little "shark fin" vortex generators and Air Tabs? I was thinking of sticking on a row of the latter on the top of my hatch door but not on the sides as they recommend.

Its difficult to get something like this done right through trial and error. Unless if you have access to a full scale wind tunnel. I know that they are used on other cars already, I think one of the earlier evos had something similar.

The reason I was thinking about a wing is that it is larger and easier to test in the water tunnel at my lab. The job is the same, to trip turbulence that will be helpful in reducing drag. The equipment I use has lasers measuring the movement of small aluminum particles in water to visualize the flow on a computer. However, unless if the changes are drastic, this equipment probably wont accurately show the influence of tabs on a miniature yaris.

BTW, does anyone know where i can find a model yaris?