r/aerodynamics

This simulation shows the initial pressure field development around a trailing edge. Edge thickness is 2mm on a foil of 1m chord. Streamlines give an idea of momentary flow direction at a given instant. It should be kept in mind that the pressure field changes rapidly and that a particular air particle might only move a very short distance before its underlying streamline again changes direction. This was part of an investigation into the time-dependent development of lift. Initial air movement creates a strong surface pressure disturbance, which refracts as a wave around the corners.

aerodynamics, lift, wing, airfoil, physics, sail, sailing

Hello, I just came across this video analyzing drone propellers using CFD simulations, and I thought it was really interesting. If anyone else is interested in the subject it's this one

https://youtu.be/m_9y4rg--DY

This is the front wing endplate of a FSAE car (USA rules) (straight line, 60kph).

More images: 1, 2, 3, 4, 5

This is a good number of iterations into a re-design. The inherent problem, in different locations to different extents, is preventing any vortex shed of the lower endplate/footplate from blowing up and dropping additional loss down the length of the car and decreasing the effective span of the front wing (ie preventing mass flow under the wing being significantly reduced with large blockage from blown up vortex). There is a lot of performance in the wing profiles from this, along with some additional load from the suction on the footplate.

This is what I have developed to so far. My intent is to start by spreading the vorticity across multiple edges/ reducing the pressure gradient over any single edge (bottom of endplate, outboard footplate curl, and slightly from the vane).

So far, somewhat irrespective of which way, I go, I continue to get this formation of loss and pink helicity on the outboard underside of the curl, which eventually blows up and compromises everything else.

I would like some help in understanding, aerodynamically, what are the driving factors in the flow field causing this, so that I could try to create and modify the geometry to prevent/mitigate it.

Thoughts so far:

• Should I stop the channel from expanding in Y as it goes downstream/should I make it more circular?
  • I dont know if this will actually change this issue, because I think regardless of the angle it sheds at, there will be some kind of asymmetry as to where the core is sitting, and pressure gradient pulling it inboard anyway?
• Should I open up a sort of slot gap on the top of curl halfway, as it starts to form?
  • example on ferrari 2013 FW
  • Have tried this on some older wings (1, 2) and not super convinced, as any loss of the trailing edge didnt seem to work nicely with the start of the second slot - although i do have a discontinuous outer edge here
• (maybe not directly relevant) but I should make the vane longer, to keep feeding some more helicity downstream

I quite a lot of experience in surface design, so ability to make any geometry is not really a factor.

The only possibly relevant restrictions realistically are:

• Dont want to change E1 and E2 (no new tooling on those)
• Front wing width cant go further outboard than centreline max of front wheel (unlike EU rules)
• Limited to Z250 (no higher than wing already goes)

Rough specs: ~2m class span, aspect ratio around 2, sweep roughly 60°/45° either side of an inboard crank, NACA 0004, fixed tricycle gear (or skids, not sure yet), single electric pusher prop, target all up weight in the low tens of kg. Elevon only pitch/roll, no tail surfaces, no rudder.

Questions I'd value input on:

1. Any concerns with elevon only control authority at this AR/sweep, particularly stall/spin behaviour near the tip?
2. Does this crank sweep combination make sense for vortex management at this scale, or would you expect issues at the discontinuity?
3. Single pusher prop with no rudder how have others handled torque/yaw on a similar tailless layout? Trim-only, or did you end up needing a ventral fin?
4. Any structural or manufacturability concerns jumping out from the render — panel curvature, gear loads, prop clearance?
5. Apart from thrust vectoring or a lift fan, what other high lift devices can i add to this to make it STOL capable (aiming for a landing of less then 100m)

Happy to share more (XFLR5/VSP screenshots, polar data) with anyone who has relevant tailless delta background.