Pickup Tail Gate Up or Down... A Scientific Explanation

[Rokeby]

More info with a scientific basis... is it the last word?

Journal of Wind Engineering and Industrial Aerodynamics
Volume 98, Issue 2, February 2010, Pages 100-112

Experimental study of a pickup truck near wake

Abstract
The present study focuses on the aerodynamics of pickup trucks. The flow
about a generic pickup truck has been documented experimentally. The main
objective is to gain a better understanding of the pickup truck aerodynamics
through mean and unsteady pressure measurements as well as detailed flow
field measurements using particle image velocimetry (PIV). Of particular
interest and complexity are the symmetric and asymmetric separated vortex
flows which develop behind the cab and the tailgate.

A secondary objective is to obtain a comprehensive experimental data set
for validation of computational fluid dynamics (CFD) models. The
experiments were conducted at Reynolds numbers in the range of 5–
8.5×105 in an open return wind tunnel equipped with two-frame digital PIV
system.

The mean pressure results of the pickup truck show that the pressure
outside the tailgate is higher than inside the tailgate suggesting that the
tailgate reduces aerodynamic drag. The root-mean-square (rms) values of
pressure fluctuations at the cab back is very low and increases significantly
towards the back of the bed and the tailgate top edge. Pressure fluctuation
spectra indicate a spectral peak at a Strouhal number of 0.07.

Velocity field measurements of the near wake flow show a relatively
quiet region behind the cab and no recirculating flow region in the symmetry
plane behind the tailgate. Instead there is a strong downwash at the
symmetry plane behind the tailgate. This downwash is due to the existence
of a pair of counter-rotating vortices downstream of the tailgate. The
downwash promotes attached flow behind the tailgate, thus resulting in a
pressure recovery that reduces drag.

From:

ScienceDirect - Journal of Wind Engineering and Industrial Aerodynamics : Experimental study of a pickup truck near wake

[99metro]

Well then, there you go. That explains a lot.

[jamesqf]

Another damn paywalled article!

[3-Wheeler]

Originally Posted by 99metro

Well then, there you go. That explains a lot.

I got a good laugh out of that!!

Maybe this will help...

SAE report: Pickup Truck tailgate aerodynamics... better up, down, or off?

Jim.

[Rokeby]

Originally Posted by jamesqf

Another damn paywalled article!

I did a lot of poking around the web trying to get around the "paywall" to see
the entire study. I was unsuccessful.

However, I did find that a one year, 12 issue subscription to The Journal Of
Wind Engineering & Industrial Aerodynamics costs a mere ...

$3628.37.

I am at a loss to understand the business plan on this.

OK, LOTF is an appropriate response:

Originally Posted by 3-Wheeler

Maybe this will help...
SAE report: Pickup Truck tailgate aerodynamics... better up, down, or off?

Jim,

Thank you. I searched EM before starting this thread and found that one.
Because this study has a different point of origin and a different
methodology, I feel it deserves to be considered on it's own.

[thatguitarguy]

If it costs that much, it must be valid...

[aerohead]

Originally Posted by Rokeby

More info with a scientific basis... is it the last word?

Journal of Wind Engineering and Industrial Aerodynamics
Volume 98, Issue 2, February 2010, Pages 100-112

Experimental study of a pickup truck near wake

Abstract
The present study focuses on the aerodynamics of pickup trucks. The flow
about a generic pickup truck has been documented experimentally. The main
objective is to gain a better understanding of the pickup truck aerodynamics
through mean and unsteady pressure measurements as well as detailed flow
field measurements using particle image velocimetry (PIV). Of particular
interest and complexity are the symmetric and asymmetric separated vortex
flows which develop behind the cab and the tailgate.

A secondary objective is to obtain a comprehensive experimental data set
for validation of computational fluid dynamics (CFD) models. The
experiments were conducted at Reynolds numbers in the range of 5–
8.5×105 in an open return wind tunnel equipped with two-frame digital PIV
system.

The mean pressure results of the pickup truck show that the pressure
outside the tailgate is higher than inside the tailgate suggesting that the
tailgate reduces aerodynamic drag. The root-mean-square (rms) values of
pressure fluctuations at the cab back is very low and increases significantly
towards the back of the bed and the tailgate top edge. Pressure fluctuation
spectra indicate a spectral peak at a Strouhal number of 0.07.

Velocity field measurements of the near wake flow show a relatively
quiet region behind the cab and no recirculating flow region in the symmetry
plane behind the tailgate. Instead there is a strong downwash at the
symmetry plane behind the tailgate. This downwash is due to the existence
of a pair of counter-rotating vortices downstream of the tailgate. The
downwash promotes attached flow behind the tailgate, thus resulting in a
pressure recovery that reduces drag.

From:

ScienceDirect - Journal of Wind Engineering and Industrial Aerodynamics : Experimental study of a pickup truck near wake

More de-fenestrated scientists operating in a vacuum,-issing away valuable research time and resources.
Please someone,buy them a window and show them how to use a search engine on the internet.