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Old 08-19-2015, 04:47 AM   #1 (permalink)
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A paper on aft-end underbody diffusers

I have found a few threads here about projects for making underbody diffusers. Here is a dissertation I found that may be of interest to some ecomodders:

"An experimental study of automotive underbody diffusers", by Lydia Jowsey, 2013. It was a bluff-body wind tunnel study that included variables of diffuser angle, number of channels and ride height. The material is quite interesting. Link:
https://dspace.lboro.ac.uk/dspace-js...013-Jowsey.pdf

At the end are appendices with data tables from full scale tests done in 2009 of a Ford Focus and a Ford Modeo hatchback. Unfortunately, the Focus model was not mentioned (sedan?, hatchback?), and these tables are not discussed anywhere in the document. Cd is provided and is of interest, but much that is in the tables is cryptic. Maybe someone else can make heads or tails out of them, particularly what led to the minimum Cd figures.

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Old 08-19-2015, 05:49 AM   #2 (permalink)
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"Submitted in partial fulfilment of the requirements for the award of
Doctor of Philosophy of Loughborough University 2013"

Philosophy??

Quote:
Originally Posted by Focus-Ak View Post
Cd is provided and is of interest, but much that is in the tables is cryptic. Maybe someone else can make heads or tails out of them, particularly what led to the minimum Cd figures.
Yeah, I skimmed through the paper. Most of the technical descriptions were above my head.

Can anybody translate this into simple terms?
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Old 08-19-2015, 07:24 AM   #3 (permalink)
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Quote:
Originally Posted by whatmaycome14 View Post
Can anybody translate this into simple terms?
Quoting from the conclusions:
Quote:
The optimum angle for downforce generation was found to be between 13 and 16.

Overall, the use of multiple channel diffusers have shown that there are merits in their application and that they significantly increase the performance envelope especially at high diffuser angles.
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Old 08-19-2015, 09:33 AM   #4 (permalink)
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I skimmed it and the salient point was provided by wdb above. Drag was not the target, maximum downforce was. No need to read into that further as downforce is a real drag :P
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Old 08-19-2015, 12:34 PM   #5 (permalink)
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But if you read it more carefully, drag is discussed quite a bit and it is covered in several of the charts. Also, it is covered in all the rows of the tables in appendixes A & B.
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Old 08-19-2015, 02:01 PM   #6 (permalink)
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"Submitted in partial fulfilment of the requirements for the award of
Doctor of Philosophy of Loughborough University 2013"

Philosophy??
Doctorate degree. Girl got her Ph.D. and is now Dr. Lydia Jowsey or Lydia Jowsey Ph.D. depending on the circumstance.

Will be reading the article later Focus-AK, thanks for the link.
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Old 08-19-2015, 02:20 PM   #7 (permalink)
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Doctorate degree. Girl got her Ph.D. and is now Dr. Lydia Jowsey or Lydia Jowsey Ph.D. depending on the circumstance.

Will be reading the article later Focus-AK, thanks for the link.
Yeah, I guess I meant more why is somebody who is getting a PhD in Philosophy doing a paper on this...

But that's not really important. The important question that we should answer is what is the best angle for US.
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Old 08-19-2015, 05:03 PM   #8 (permalink)
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paper

Without wheels,the model seems way too simplistic to dovetail any results into real world expectations.
The presence of wheels can alter the drag by 2X and their addition to the model would significantly affect performance of the diffuser(s).
The info on the Focus car would have been more useful.
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Old 08-19-2015, 05:47 PM   #9 (permalink)
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Quote:
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Yeah, I guess I meant more why is somebody who is getting a PhD in Philosophy doing a paper on this...

But that's not really important. The important question that we should answer is what is the best angle for US.
It is just an oddity of a long tradition in the academy. It does not mean she studied Kant and Hegel. It means she completed an advanced degree in research. Once upon a long time ago, it was almost all "philosophy" ... think Aristotle and Plato... all the modern fields of inquiry evolved from that tradition, splintering off. Many still have the Ph.D. ... Physics ...

Here is a sjmilar degree from UKansas: Doctor of Philosophy in Aerospace Engineering: Degree Requirements - KU Catalog

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Old 08-19-2015, 05:51 PM   #10 (permalink)
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Quote:
Originally Posted by whatmaycome14 View Post
Yeah, I guess I meant more why is somebody who is getting a PhD in Philosophy doing a paper on this...
It's not intuitive. PhD means philosophy doctor, and it goes back a few hundred years to early colleges, where science was considered an arm of philosophy (use of logic, etc.). One science journal a few hundred years old is Philosophical Transactions of the Royal Society (now published in two segments: Home | Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences and Home | Philosophical Transactions of the Royal Society B: Biological Sciences). See also: https://en.wikipedia.org/wiki/Royal_Society.

Dr. Jowsey's Phd is in automotive engineering (an applied science).

And of course, since things mushrooms, there are now PhDs in music, sports, etc.

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