Stability of passenger vehicles following tractor trailers

[waterguy]

Good day,

Does anybody know of any research that has been done to look at the affects that turbulence generated by a transport truck (tractor trailer) would have on a passenger vehicle that is following the truck ? I've come across some material involving passing maneuvers and its affect on the passenger vehicle stability, but nothing related to following vehicles.

I'm trying to see if this could be a viable fluids project. Unfortunately, most of my experience is in hyraulics so I'm not entirely familiar with the type of reserach/information that is avialble for road vehicles.

Regards,

John

 

[Haf]

If you're looking at this as a potentially viable fluids project, you may want to start on a simpler level. Look for research on the wakes created by blunt objects (such as rectangles). I'm sure there's lots of stuff out there. I know there's also research that has been done that characterizes the air flow around tractor-trailors. Some of this research has been concerned with decreasing drag (by adding various appendages to the cab) in order to increase fuel efficiency. Since the wake profile will have a large impact on drag, I'm sure there's some good info in there (as well as comparisons to baseline cases, i.e., cases that don't have those appendages). I'm not sure if theres research on how that wake profile affects passenger cars behind the trailor.

If your main concern is precedence (i.e., you want to work on a problem never worked on or solved in the past), then my answer to your question is I have no knowledge of any such research. But just in case I don't know everything (a distinct possibility!), I'd do a literature search at a technical library.

Have fun!

Haf

 

[Slice]

waterguy,

I've seen truck wakes mentioned in some simple automotive aerodynamics books. One of the key aspects of this problem is a periodic wake phonemenon. Vortices are shed off one side of the trailer, then the other but not at the same time. The frequency(period) must be directly related to the reynold number involved. I think blunt-body research is the perfect place to start as Haf pointed out.

The effect of the unsteady air on the passenger vehicle's stability is a whole different problem. If you're planning to study the effect on a "typical" passenger vehicle, there are plenty of automotive aerodynamics books... Joseph Katz is one author that i can think of off hand.

I think that this problem is worth studying if the standard passenger sedan weighed 500 lbs less..

good luck

SB

 

[sciguyjim]

If I may, I have a somewhat off-topic question. Is it possible for a car to draft behind a semi without being at a dangerously close distance? At what distance is drafting possible? Approx how much would it affect your mpg?

 

[IRstuff]

As a guess, one might expect a distance comparable to the width or height of the truck.

This is consistent with the design of boattailed ammunition.

If you watch auto racing or bicycle racing, you can see that the drafting process essentially requires absurdly close distances that cannot be sustained with an uncooperative or unaware lead vehicle.

TTFN

 

[sciguyjim]

Thanks, I was just curious.

 

[kafeel]

Hi,
there are quite a few journal articles on the wind profiles of truck-trailers. If you search in the 'Journal of Wind Engineering and Industrial Aerodynamics' you should come across some interesting research work.
One of the most active scientist is C.J. Baker.
A book by Hucho 'Aerodynamics of Road vehicle' gives good basic knowledge, which would be handy.

All the best