His original post showed exactly that as one of the options.
Nope, only one slightly lower along with a second higher bottle further forward
Iâm talking about the thumbnail labeled â1 bottle frontâ with a 0.216cda. You mean something else?
Thatâs got the bottle further forward and between the arms at the height of the elbows, what Iâm seeing is bottles above and behind the elbows.
Thanks for this. For running these kind of simulations would you be willing to share a few specifications of your model? Such as total number of cells and how you are handling the mesh within the boundary layer? I use OpenFOAM for my simulations, typically running RANS simulations. I have not done a model quite in this configuration but have run upper torso, arms, thighs, head. I use âlayersâ in my meshing in the boundary layer - cells shaped like thin bricks kinda, and try to get 10 layers of layers (if that makes sense) within the boundary layer. Often I only succeed in getting around 7 layers. Total model size is, if my fuzzy memory serves, usually around 50 million to 60 million cells. Higher resolution near to the subject, courser further away.
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Happy to share some details. I linked two papers higher up in this post to mesh sensitivity done by Blocken and that has been my starting point. So k-omega turbulence model, SST, resolved the boundary directly (no wall functions, so same as what you are doing). 10-15 boundary layers.
We did a lot of work getting the cell count as low as possible whithout affecting the results. The boundary layer mesh is critical and a small area directly behind the rider, from there you can scale up the refinement zones quite aggressively without any downside.
We also do a couple cool things how we initialize the mesh parameters and what we do with relaxation and convergence parameters to get to a good result quickly.
Through all those optimizations we were able to get to a good mesh with just under 10M cells from memory
Thanks for the reply! Have you found any sensitivity to controlling the boundary layer cells in the âlayerâ shape vs standard cell shape? I have no problem getting 10-15 cells deep in the boundary layer but I do have a problem getting more than 7 of those to be of the âlayerâ variety. I donât know if youâre familiar with OpenFOAM - Iâm using SnappyHexMesh for meshing.
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I use openfoam and snappyhexmesh too for this. I can look through my allmesh files in the next days. Ill probably DM you. As much as people like technical rabbit holes, debugging snappyhexmesh scripts is probably beyond the scope of a Tri forum.
This makes me wonder if those saddle-mounted splash guards might be useful to prevent the separated flow off the back from getting sucked into the low pressure zone behind the riderâs hips.
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You might be surprised at the level of detail folks around here like to see, even if itâs new to them 
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Arenât fins in the center wake of a bluff body generally a good thing aerodynamically? At best, they can lessen vortex shedding, and at worst they sit there in dirty air with very little frontal area.
There may be some cases where itâs a net loss but Iâm not familiar with them.
Finally got around testing the high position:
It tested almost the same as the lower bottle location.
Will do AssSavers next, thats a good idea. Is there a rule against mud guards in triathlon?
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You are spot on. Most of the engineering text books in my opinion are from the US or UK, but there is one German author that is high on my all time favorite list:
https://www.amazon.com/Aerodynamics-Road-Vehicles-Engineering-Proceedings/dp/0768000297
Its is a more applied book for a scientific text book that gives many actionable advice that is applicable to cycling aerodynamics as well. If anyone wants to take a deeper dive beyond magazines and forums, that would be the book to get.
Even better is his book on Bluff Body Aerodynamics: âAerodynamik der Stumpfen Koerperâ but I have only seen it in German.
I have a hard time picturing that. Can you draw it?
Like the twin aero bottles the Bigham/Dowsett TTT in Sub7 had fitted behind the saddle but rotated 90 degrees.
Skipper was the protected athlete
I want to say someone tested an ass saver in the wind tunnel and it wasnât stiff enough to actually influence the airflow. Be interesting to do a coupled fluid/structual analysis and see what happens though. Theyâre definitely allowed though, no issues there
Good to know they are allowed. Seems like if they werenât stiff enough, it would be easy to see the flutter (a-la race belt numbers) when riding.
There are designs that have added vertical rigidity (see below), so if the concept is valid, adding the necessary rigidity should be doable.
This, but rotaed 90â°
