Red Bull had a strong pre-season test, with the team widely believed to be at the front of the grid ahead of the first race this weekend – the Milton Keynes outfit has not been in such a strong position since it last won a title, in 2013. When the team revealed only two images of its new car at the RB16B’s launch, there was little difference apparent to its predecessor. However, now that the entire exterior of the car has been photographed, there are a number of developments on show.
Starting at the front of the car, the front wing has mainly been carried over from the design which the team introduced four races from the end of last season. However, there has been some development outboard, with more aggressive elements and the addition of a gurney flap. When the new front wing regulations came into force in 2019, Red Bull’s initial concept focused on an outboard loaded front wing, which increases the outwash due to the span wise pressure gradient set up along the wing. However, the difficulty with this lies in maintaining the health of the outboard vortices, particularly when the front ride height is low and the roll is high. Therefore, over the past couple of seasons, the team has headed towards a more inboard loaded wing. The 2021 wing subtly reverse this trend, putting more load outboard. It may be that the team now feels confident enough in controlling the outboard structures that this direction is positive overall.
Further rearward, the bargeboard development approach has also been evolutionary, building upon the design of the RB16. The main bargeboard trailing edge has been moved back for 2021, while the leading edge appears to be similar. In making this change, the camber line of the main bargeboard will be altered, and this has allowed the team to further sweep back the tips of the multitude of upper elements, while still being legal in terms of shadowing these elements when looking from below. Sweeping these elements rearward should enable the centre of vorticity shed of the top of the bargeboard to be kept higher as the vortices roll-up and propagate rearward, reducing the interaction of the vortex losses with the floor leading edge.
Regarding the edge of the floor, which has been heavily impacted by the revised regulations for 2021, Red Bull initially ran with a solution similar to that it tested at the end of 2020 during Friday practice. However, over the test, three additional elements were added above the floor, while the floor edge was stepped in mid-way along its length, something that many teams have on their cars. The two additional rearward elements will look to split up the main floor edge vortex by introducing two additional vortices, with the aim of reducing losses in the diffuser and altering the position of the vortex cluster once it has rolled up into a single core.
Looking at a rear view of the 2020 and 2021 cars, it is clear that there are a number of significant changes. The 2020 cooling exit shown here is the one run in Bahrain last year, and therefore should be fairly comparable to the 2021 design used in testing. The new exit has been raised significantly, particularly at its base, greatly increasing the clearance to the top surface of the diffuser. This will improve the onset flow to the diffuser flaps, preventing any of the poor quality flow exiting the internals of the car impacting on their performance, increasing their load locally but also working the entire diffuser harder as the effective expansion is increased.
The now-single exhaust wastegate has been placed below the main exhaust for 2021, which should reduce losses further. Note that the upper wishbone shroud is no longer twisted to the same extent as it was in 2020, with more downwash apparent outboard. This will load the outboard of the rear wing mainplane leading edge and reduce drag, at the expense of downforce on the wishbone itself. Also note the raised rear lower wishbone, something that will further contribute to diffuser performance. Either the diffuser kick-line can be more aggressive without the losses on its top surface being too extreme from the interaction with the wishbone, or the diffuser flaps will receive better onset flow for the same kick-line.
Further outboard, the upper wishbone has been raised, which will improve the performance of the winglets around the rear brake duct. Additionally, the shroud around the rear lower wishbone has been re-profiled, with the slot from 2020 removed and the element above it becoming longer in chord, especially at its root.
Red Bull ran two different diffusers during testing, with the second one shown below – this appears to be the team’s preferred option. Comparing back to 2020, there are a number of changes, aside from the trimmed inboard fences that are mandated by the regulations. Starting at the centre of the diffuser, the blend around the ‘corner’ of the central ramp has been softened, which may offer a small improvement in flow quality. The trimmed fences have reduced the outwash in the diffuser, and Red Bull has tried to recover this by increasing the angle of attack of the two inboard fences.
The inboard fence is very important in smoothing out the adverse pressure gradient experienced by the centre ramp as it recovers from both vertical and lateral expansion, and trimming this fence will have offloaded it considerably, losing the smoothing of this pressure gradient. In addition to generating more outwash to support the outboard of the diffuser, this probably also explains why this fence is more aggressive this year. Of course, it is also important that the fences do not separate, although one of the benefits of the shorter fences is the tip vortex can support the suction surface better, particularly at the root, where attachment is usually hardest to maintain. Note also that the diffuser trailing edge kick is more pronounced behind the most inboard fence for 2021. This should increase the load locally, thereby reducing the pressure recovery required at the root of the fence, keeping it attached. Lastly, note the reduction in height of the final tip on the two inboard fences, and the trimmed outboard fence.
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