So I've done a little leg work and looked through the regulations and understand which sections can be switched out for the race type and qualifying/race, which could make for some interesting strategical decisions throughout events/the season, I guess.
IndyCar.com shows the areas that can be homologated by the aero manufacturers in red, which in brief include the front wing, sidepod panels, engine cover, rear wheel wedge, rear wheel crash bumpers and rear wing. Honda and Chevrolet have looked at this differently and come up with aero kits that look outwardly different so lets take some time to look at what they're looking to achieve.
Lets kick things off with Chevrolet as they're already the ones to beat
https://youtu.be/LIcXf0WBkAE and show the differing CFD plots for the outgoing DW12 aero kit compared with the new Chevy kit for 2015. Just focused on the front wing for now lets see what they've changed and what affect that is having...
I think the first thing to note is that Chevrolet have taken the Dallara design and simply looked to improve it, rather than going for an all new radical design concept.
In terms of the mainplane the shaping is retained until the outer section with the wing extended to almost the cars full width, which means contolling the front tyres wake much more effectively (tires for my American friends). The outer section of the wing is normally home to an endplate, used to increase the aspect ratio of the flaps that sit inboard of it. However, the Chevy kit doesn't have a conventional endplate, but rather a Venturi which funnels out toward the tyre (see below, yellow).
Moving onto Honda and from the outset the Honda front wing looks much more like the type of thing you'd expect to see from an F1 team, albeit one with a lower budget.