another vortex generator paper

[cyclopathic]

Originally Posted by aerohead

The Mitsubishi paper is probably the gold standard for automotive-related VG application.As an aeronautical company (you may remember their products from Pearl Harbor,December 7,1941) Mitsubishi is well acquainted with all things aerodynamic/hydrodynamic/gas dynamic.
Their science is water tight.
This paper is part of my library.
Unfortunately,some under-graduate,and graduate research on VGs,is being passed along without a jury peer review at their respective university,and would never pass the scrutiny of an SAE Congress,where most research papers are presented each year.
Too bad! These 'leaks' don't reflect favorably on the reputation of the college or university.

4 inches apart, 4 inches in front of flow separation; that is all you need to know as an engineer. I understand your concern of low quality research papers, but then again people who did extensive research on airfoil VGs not really keen Mitsubishi paper.

With respect to the article think this way: to prove that earth is round and rotating around sun you don't have to calculate its diameter and orbit.

[aardvarcus]

I hesitate to get into this quickly degrading thread, but as an engineer myself if an engineer doesn’t understand the math, science, formulas, and constraints behind any product they are utilizing, I question their abilities as an engineer. You will not last long in most industries quoting “rules of thumb” without being able to fully explain how and why. The handful of “engineers” (and I use that term loosely) that somehow exist just glazing over data and making broad generalizations are the reason most hardworking blue collar employees hold disdain for engineers. And frankly I don’t blame them and share in their disdain towards certain individuals. Those “engineers” should find another career path.

It doesn't matter to me whether vortex generator's induced vorticies net reduce your drag coefficient times area figure or not, I have no skin in the game either way. But in my opinion papers with improper testing methodology are worse than no paper at all, regardless of the subject area.

[user removed]

Brilliant engineering, maybe they needed vortex generators.

regards
mech

https://search.yahoo.com/yhs/search?...&hsimp=yhs-003

[aerohead]

Originally Posted by cyclopathic

4 inches apart, 4 inches in front of flow separation; that is all you need to know as an engineer. I understand your concern of low quality research papers, but then again people who did extensive research on airfoil VGs not really keen Mitsubishi paper.

With respect to the article think this way: to prove that earth is round and rotating around sun you don't have to calculate its diameter and orbit.

So far,I've been acquainted with at least a half-dozen different types of VGs.Each has it's particular merits and liabilities.Some are super-boundary layer height.Some are sub-boundary layer height.Position and spacing are all over the map,depending upon the specific application.
All VG applications are approached on a case-specific basis.
If you have a Mitsubishi Lancer notchback exactly as in the research paper,then you're free to mimic exactly what was done and expect a favorable outcome.
If however,you have a different vehicle,then all bets are off.You must start from the beginning.The type,size,location,and spacing of the specific VG which delivers the optimum performance will be determined only after much investment.
To add salt to the injury,the gain from VGs is so small that their contribution to drag reduction can be lost in the signal-to-noise ratio of road testing.Without full-scale wind tunnel testing one might never figure out what they had.
They can be analyzed numerically,but you're talking 2+ days,running on a super-computer for a single iteration.I don't even know how you'd develop the digital file (millions of panel elements/marker and cell) to accurately portray the vehicle,plus VGs.
I don't know any aerodynamicist that would dare use some shoot from the hip,generic,one-size-fits-all approach.

[cyclopathic]

Originally Posted by Old Mechanic

Brilliant engineering, maybe they needed vortex generators.

regards
mech

https://search.yahoo.com/yhs/search?...&hsimp=yhs-003

Yeap from the guy who designed Manhattan and Golden Gate bridges

[cyclopathic]

Originally Posted by aardvarcus

I hesitate to get into this quickly degrading thread, but as an engineer myself if an engineer doesn’t understand the math, science, formulas, and constraints behind any product they are utilizing, I question their abilities as an engineer. You will not last long in most industries quoting “rules of thumb” without being able to fully explain how and why. The handful of “engineers” (and I use that term loosely) that somehow exist just glazing over data and making broad generalizations are the reason most hardworking blue collar employees hold disdain for engineers. And frankly I don’t blame them and share in their disdain towards certain individuals. Those “engineers” should find another career path.

Look this way: the example above from old mech (Tacoma Narrows bridge) was designed by brilliant engineer, who used it as a basis for writing book which advanced suspension bridge design. Tacoma bridge collapsed in 5mo.

Egiptian pyramids were designed by people who did not "understand the math, science, formulas, and constraints behind any product they are utilizing". Last time I have checked they were still standing.

[aardvarcus]

If his bridge collapsed… reread my post. He obviously did not understand the constraints and technologies of the products he was using. I understand he was pushing into new territory and bridging state of the art, but that in my mind means you should understand your constraints and limitations even better. It is a bridge; people’s lives are at stake. We all know that if he would have just boat tailed the bridge using the AST-II template it would have been fine. [/joking]

I believe you may be mistaken about the Egyptians. Anyone who figured out how to add a curve to “straight” pillars to make them trick the eye into appearing perfectly straight by using the suns rays to project such a gentle curve it couldn’t practically be reproduced by typical means (string curve would have been many miles long) is a pretty darn brilliant engineer in my book. Makes me look pathetic by comparison. Just because they didn’t have calculators and libraries of textbooks doesn’t mean they didn’t understand. They didn’t have to know calculus or be able to solve differential equations, they just needed to understand the products they were using. Stone isn’t that complicated, but they used it to do complicated things. In fact I bet they understood their resources and products better than most present engineers who take the immense wealth of knowledge available at their fingertips for granted.

[Xist]

I really do not think that the pyramids are a good example. Mountains are naturally occurring and generally do not fall down, either.

[fbov]

Originally Posted by aerohead

The criticism was leveled directly at the testing methodology and ignorance on the part of the investigators....Please reread my comments.I don't appreciate people putting words in my mouth.

No more than I appreciate people replying to posts they haven't read.

As I stated, your criticism is aimed directly at student work, where ignorance is to be expected and poor methodology the norm. You criticize the student for trying to learn. Shame on you.

In terms of your football metaphor, this paper is on the practice field. No ref's, no flags, only coaches. If the lead author were a PhD, if it were published in peer review journal, etc., that would be different.

Have fun,
Frank

[aerohead]

Originally Posted by fbov

Keep throwing the caution flags, but throw them at the right thing.

An Indian grad student's paper showing empirical verification of theoretical modeling only proves that CFD makes testable predictions with a degree of accuracy. This isn't a VG paper, they just use them as a matter of convenience, as their properties are well known. Standard academic procedure.

The Mitsubishi paper is interesting, as it's clearly aimed at performance improvements. Those familiar with car aerodynamics (or at least with Hucho) know this test is rigged. The Lancer rear window is too steep to maintain attached flow past the roof. 14 degrees is the transition, IIRC. Mitsu's doing good engineering here.

VG's work wonders in certain applications, as on airplane wings. Not so much elsewhere; throw the flag at the offender, not the tool.

Frank

*I'm to throw the flag at the right thing.
*I criticized the methodology and results.If this data passes without rebuttal,then there's a danger of it passing as knowledge.
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*I see zero empirical validation of theoretical modelling,nor proof of anything.
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*The entire paper is predicated upon vortex generators as is clearly stated in the title header.
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*VG properties are clearly known to who?
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*Why is the test rigged? Gary Wheeler's VGs are clearly targeted to notchback cars which all suffer separation-induced drag penalties.Wheeler's VGs are well known in the aerodynamic/aeronautical community.Mitsubishi would be no exception,when embarking on their investigation.
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*"VGs work wonders" .You are a devotee of VGs? Am I slamming VGs?
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*Are VGs the 'offender' ? I should criticize VGs and leave the students alone?
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*Or do I leave VGs alone and comment on a paper which has no scientific merit and perhaps should have stayed within the confines of the university,if they were actually attempting to push the state-of-the-art?
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