Pickup truck vortex used on a car?

[aerohead]

Originally Posted by cyclopathic

So the fact they have PhD is invalidated because it is in India? What type of degree do you have?

With respect to "Surface details this small cannot be analysed with anything below a 1/2-scale model" were exactly this was discussed? That is a clay model not a car!

*whether they have a PhD or are from India is not germane to the topic.
*I have a B.S.,Mechanical Engineering Technology.
*Where these criteria were discussed is nowhere in their presentation,as they obviously didn't know what they didn't know with respect to aerodynamics,or dynamic similarity,and it reflects the fact that they don't understand critical Reynolds number and verisimilitude (absolutely critical to testing success),which is discussed elsewhere in the literature I've studied over the last 40-years.
*Of course it's a model.
*The PhD's who run 'real' wind tunnels have published reports stipulating that certain body features cannot be adequately tested at scales below 1/2-scale,sometimes it requires full-scale testing,or full-scale CFD.

[aerohead]

Originally Posted by cyclopathic

putting aside discussion on how flawed the study is or isn't it had shown that vortex generators can improve existing aerodynamic features and may produce better results than spoilers alone, when applied properly.

With respect to critique.. Scale is wrong? may well be, if it were a replica of real car. But they used generic "sedan" shape, so wrong comparing to what? "Surface details this small cannot be analysed with anything below a 1/2-scale model" would have been the case if once again we were looking at real car, with panel gaps or window seals or wipers or grills to look at, but on clay model? You can argue that 68.1% drag reduction is unrealistic in real car applications, that if the real car model was used and you were trying to scale result to original. But these arguments just point out the limitations of lab experiment results; it is not like the general principle is invalid.

Perhaps you could make an argument that vortex generators only work at high flow speeds, but this is not a case. The existing applications in aviation on small planes like Cressna had shown that VGs help to reduce wind stall speed from 60 to 45MPH. Well within general car speeds. They also reduced top speed by a couple MPH, so there is no question that VG generate additional drag.

*You are correct,in that VGs have been shown to reduce overall drag on notchback cars,SUVs,and Vans.
*The Mitsubishi Evo Lancer registered a maximum 1.7% drag reduction with delta-shaped VGs.
*An SUV and van registered 4.2% and 10% reductions respectively in a different investigation by different investigators.
*The Lockheed C-130 Hercules has undergone VG,stubs,nubs,microvane,and sub-B.L. VG drag reduction investigations for its up-swept underside to good effect.
*The report from India was extremely flawed in execution and follow through,but is no reflection on you.

[slowmover]

Originally Posted by aerohead

Here's a rendering of a quasi-commercial setup which combines the wing and box into an aerodynamic boattail/box-cavity/storage container.
It rolls up to the SUV/wagon receiver hitch on four castor'd pogos,which rise and stow into the belly while on the road.
3-4 mpg.

Lots of pie-in-the-sky stuff on this forum. Part of its fun.

This idea should be well known. Trunk & aero devices.

The Highway Pack for the SUVs.

Would even work with trailer-Towing.

A tail is also beneficial in handling cross-winds. There’s a point where the extension becomes a lever, but it’s fairly high up there in wind speed.

Meaning: less work at the steering wheel thru the day. Today’s computer integration of drivetrain inputs isn’t going to be bettered by the driver. The driver already has enough work what with road, load, traffic and weather.

Judging conditions to alter speed to best accommodate NO lane changes and being able to maintain lane CENTER without corrections is where Interstate Highway mpg resides.

67-mph may be do-able prior to dawn and in earliest morning. But once traffic escalates, the penalty becomes too high (Safety & economy track for discussion purposes). It may only be 64-mph the better part of the day. Fuel burn will be about the same. MPG isn’t simply wind resistance.

Aero aids that allow the vehicle to more smoothly handle gusting and constant winds reduce Steering degree of input AND duration.

My day at the wheel is FAR EASIER when I have a 53’ van with skirt & tails. I get an extension against the clock of when fatigue takes over at the wheel.

.

[kach22i]

Originally Posted by PaulB2

There is that diagram floating around here about pickup aerodynamics, which shows the small wing on the roof and a half tonneau being the best aerodynamically. I imagine (correct me if I'm wrong) it establishes a stable vortex in the pickup bed, and the air just flows over that vortex down to the tonneau cover. I just wondered if we could move this to the back of my volvo (if I buy one).

I believe the Texas University PDF diagram shows full aero-cap on the bed being best as it retains air attachment.

In addition as I recall the diagram shows a full tonneau cover as being ever so slightly superior to a half cover in any condition including with or without roof wing.

I think you are comparing apples to oranges anyway, long body ratio station wagons are nothing like pickup trucks aerodynamically speaking.

You may wish to lengthen the cab or wagon with a rear spoiler or roof wing so the air has a clean and defined detachment point that forms partial box cavity. That is one of the only commonalities I can think of.