It appears that my response to this post has been removed entirely.gordonjudd wrote: ↑Mon Jan 09, 2023 5:00 pm
Vince,
I don't understand why the ambient air itself would generally be turbulent. Is that the case when the air is still (i.e no wind) as well?
This quick search on turbulent ground air seems to say it takes relatively high winds for the air to become turbulent.How much wind causes turbulence?
The stronger the wind speed (generally, a surface wind of 20 knots or higher is required for significant turbulence), the rougher the terrain and the more unstable the air, the greater will be the turbulence.Evidently that is also an accepted approach in studying drag effects on inclined cylinders in air or water.Since fluid dynamics effects are so nonlinear I would tend to think that the superposition of skin drag and form drag effects might be a bit chancy but is seems that is what is done in most of the papers that I see that are describing drag effects on fly lines.
superposition_claim.jpg
Gordy
Allegedly, Heisenberg said:
Wind is not the sole cause of turbulence, it is a complex subject and some of the causes are discussed on the Ambient Air turbulence thread.When I meet God, I’m going to ask him two questions: why relativity? And why turbulence? I really believe he’ll have an answer for the first.
viewtopic.php?f=11&t=3862
Regarding superposition, it is noteworthy that it is an approximation. The fidelity of aerodynamic modelling is proportional to the size of your budget and even complex models can have large error bands when subjected to verification.