Dear Petr Michálek

The designation Horseshoe vortices is given to a form of structure with the same topology but different origins.

The first source is the transition from laminar to turbulent boundary layer, are also called vortices harping the horseshoe vortices (some authors differentiate these two intensity by more than by the shape) that are created by the laminar boundary layer as a succession of instabilities (instabilities of Tollmien-Schlichiting => lambda vortices => hairping or horseshoe vortices ). Analytical studies of this type of training you are going to find in some books and papers from the 50s and 60s.

The second source is also in the boundary layer, but in turbulent boundary layer which was detected coherent structures with the same topology. The procedure for forming is not the same as before and there is no analytical physical models which describe accurately, but there are detecting in experimental and mathematical simutation .

The third and last, the horseshoes behind structures to me perish be caused by different phenomena (I think the first must have originated in a pair mode instability and the last one mode odd, not sure???).

Therefore, for each type of horseshoe vortex generation have different conditions in the boundary layer (laminar and turbulent) or after obstacles.

I should have more information to give a more complete and indicate bibliography.

Could you please write more about second and third type or give me some recommendations about literature? I wonder what are the conditions for horseshoe vortices to rise around obstacles in turbulent boundary layer flow in a wind tunnel. Thank you.

Dear Petr Michálek.

To begin to study one subject is good to start at the beginning! It is evident, but few do it.

There is a excellent review about coherent structures in the turbulent boundary layer, called:

Coherent motions in the turbulent boundary layer, Stephen K Robinson in Annual Reviews in Fluid Mechanics 1991.23:601-639.

As is a former paper you will not find the latest news in the matter, but the strength of the article is given by the number of references to him there (over 1400).

He shows the matter didactically, starting from the definition of Coherent Structures, notation, examples, with an emphasis on structures that you are thinking about studying.

After reading the background, you can better define your object of study, you can even search through more than 1400 references to the article (many of 2013!).

If you want more tips, you can write for me. ([email protected])

Dear Petr Michálek.

For the third type of structure, I recommend research articles of sediment transport, as this subject is lacking correlations between turbulence and transport capacity.

But be careful as to transport the sediment has two distinct mechanisms (second and third) a diffuse throughout the entire bed, wherein the mechanism described in the previous section and a second mechanism ,localized erosion, also caused like structures by horseshoe vortices. The difference between them is the origin of the horseshoe vortices, but study as much as the other one are critically important (technologically speaking) and provocative (scientifically speaking).

I grabbed a random reference on localized erosion (recent studies) . I did not look carefully, so I can not make a same recommendation as the previous article, but just one example.

Coherent Structure Dynamics and Sediment Particle Motion Around a Cylindrical Pier in Developing Scour Holes DOI: 10.2478/s11600-012-0068-y

I have read some papers about turbulence and I have recognised that this coherent structures like horseshoe vortices appear also in fully turbulent boundary layer. We had this experiment: https://www.researchgate.net/publication/257863769_Ground_emission_source_and_test_model_building Could the emission source (white square) cause production of horseshoe vortices more than the ambient surface? Source is filtration fabric, ambient surface is painted wood. Does this affect emission dispersion in front of the model? Thank you for your kind advices.

Data Ground emission source and test model building