More drag reduction studies
 

Searching for the author of the paper Vekke posted on drag reduction for the A2, hoping to find more on the rear box fairings, I found a separate paper that expanded the reporting of the "box cavity" findings seen in the paper Vekke posted: "Base Pressure Recovery using Rear Cavity and Base Plates".

And for future reference, in case the longer list of papers paulu found are taken down, here is the "table of contents" for the site:

Session 0-1 - Mike Dickison, Programme Manager Coventry University LCVTP
An Introduction to the Low Carbon Vehicle Technology Programme.

Session 0-2 - Peter White, Professor of ThermofluidDynamics Coventry University, Chairman Automobile Division IMechE
Reducing carbon emissions does aerodynamics matter?

Session 0-3 - Chris Johnson, director, design project work coventry university
Aesthetics and aerodynamics

Session 0-4 - Trevor Haynes, Coventry University
LCVTP Workstream 12: Aerodynamics Technical Introduction

Session 0-5 - Trevor Haynes, Coventry University
Aerodynamics and Electric Vehicles

Session 1-1 - Scott Porteous, Development & Simulation Ricardo UK Ltd
LCVTP Workstream 12 - Aerodynamics Efficiency - Sensitivity Analysis of aerodynamic drag over various drive cycles

Session 1-2 - Gianluca Orso Fiet, MIRA
LCVTP Aerodynamics Process Development

Session 1-3 - Rishi Gupta, Mechanical and Automotive Engineering Dept. Coventry University
LCVTP WS 12 Aerodynamics Support Activities at Coventry University

Session 2-1 - Remus Cîrstea, Coventry University
Effect of rear body taper on a simple body

Session 2-2 - Jeff Howell, Tata Motors European Technical Centre
WS12 Aerodynamic Performance University Research Projects Base Pressure Recovery

Session 2-3 - Nick Sabrazat, MIRA
LCVTP Aerodynamics Reference car finding:Lessons learned

Session 2-4 - Adrian Gaylard, Technical Specialist Aerodynamics Jaguar Land Rover
Base Pressure Recovery using Rear Cavity and Base Plates

Session 3-1 - Jeff Howell, Tata Motors European Technical Centre
WS12 Aerodynamic Performance University Research Projects Wheel/Wheelarch Drag

Session 3-2 - Adrian Gaylard, Technical Specialist, Aerodynamics, Jaguar Land Rover Drag Reduction Through Wheel Design

Session 3-3 - Nick Sabrazat, MIRA
Wheel Arch Flow Investigation

Session 4-1 - Hussain Ali, Tata Motors European Technical Centre
Drag reduction on a production vehicle

Session 4-2 - David Plummer, Design Institute Coventry University
Aesthetic Design

Session 4-3 - Adrian Gaylard, Technical Specialist, Aerodynamics, Jaguar Land Rover

Further Opportunities
Posters
Posters 1
Posters 2

http://wwwm.coventry.ac.uk/researchn...ple%20body.pdf

This article is IMPORTANT. I recommend you save it, read it, and learn it.

This article is saying you can reduce drag 40 percent by making a tail. And the tail does not have to be very long.

And according to them, 20 degrees is about the absolute max, and even at that you are going to have problems with the bottom, but it is still worth it.

This article is worth SAVING.

Very interesting. Some of it looks like a section on tail end shapes in Hucho, but this has more images and discussion than what I recall. There are a few articles in that table of contents that should be of interest here.

Did I read correctly in thinking that 80 degree taper = 80 degree angle from the vertical tail section, or 10 degree diversion from horizontal?

I guess so, 90 degree would be level, so 80 degree would be 10 degree off from level position, that is how it seems to be when comparing pictures on that document as 70 degrees is much more steeper angle, meaning it is 20 degrees off from horizontal.

edit:
For 1.33m height, one after body would be 0.1064m long so two would be 0.2128m long, which would then need to be angled to 10 degrees angle downwards from trailing edge. That sounds horribly lot what I had in my car last summer and would explain my fuel economy gains a bit, even I did not have full height sides or bottom in there, also it means that there is lot more to be gained.

I read it as 80 degrees is 10, and 70 degrees is 20.

I also read it as 20 is probably fine for the top of the roof, and 20 works for the sides, but does not work for the bottom of the car unless ground clearance is "right".

The base cavity and base plates kinda blew my mind. I don't think Hucho addressed either so that was a great surprise. It is also interesting that they claim large gains from such short cavity lengths.

I was also totally brown away by the base plates. I would have thought that there would have so much turbulance between the body and base plate that it would have been counterproductive. Definitely some new ideas here.

What you thinking Phil?

Hucho
 

Hucho addresses this technology back in the commercial vehicle chapters.These plates are exactly what Continuum Dynamics developed at NASA Ames Research Center,Palo Alto,California decades ago.
I did one of these 'egg crate' boat tails behind my semi model and it flowed just fine.
By limiting where the air can be,and providing locked-vortices all around,the outer flow can skip over the egg crate as with Texas Tech's cab wing/half tonneau on the pickup.
They're not as good in a crosswind,but they're way out ahead of nothing,extremely light,easy to manufacture,and should cost very little.

The pick-up rear gate / partial bed cover seems a good analogue when trying to understand how these base plates work.

And when disguised as a cargorack or bikerack, or actually doing double duty as a rack, it won't draw that much attention.

( Actually, to be fair it should be mentioned that Paulu made note of the studies posted here on page 2 of the original thread - but its good to have a dedicated thread on this. )