Quote:
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.
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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.