ANALYSIS: A first look at Mercedes' astonishing new update for the Official Pre-Season Test
The rumours that Mercedes were bringing a significantly different W13 to Bahrain testing have proven to be true – the car has dramatically narrower sidepod inlets.
In place of the original frontal bulge, which housed quite big radiator inlets, is a dramatically narrower housing that slants heavily inwards at the top when viewed from straight on. This forms a narrow vertical triangular slit for the radiator inlets.
It’s not clear if the radiator layout within has been changed or – more likely – a more effective route for the cooling has been devised, which gives a higher speed to the cooling air. Further back, the sidepods are much as they were before.
Right from the start the W13 has featured an extremely wide outer floor channel, and what this latest change has done is give the airflow a wider entry point to that channel. The air going over the floor here generates its own positive pressure, which in combination with the low pressure beneath the floor, creates the downforce.
This new housing is just in the part of the car where the venturi inlet tunnel is ramping downwards – and that difference in pressure around this outer front corner of the floor will play an important part in accelerating the speed of the airflow down that venturi inlet. The greater the pressure difference, the faster that venturi airflow will travel and the greater the downforce.
But just as importantly, the creation of this extra space at the front of the outer floor will help feed those very wide outer channels, funneling the air to the back, through the coke bottle section of bodywork and exiting in between the rear tyre and the venturi exit ramps. The more this flow can be used to draw upon that coming throuugh the venturis on the underside, the more downforce those venturis will produce.
Accompanying the sidepod change, the floor’s wavy outer edges have been replaced by a conventional straighter edge with a single ‘curl’ part-way along to create the vortices the aerodynamicists will be seeking to further energise the venturi flow.
It could be that with the bigger volume of outer flow enabled by the wider space at the front of the floor, a single bigger vortex is now more feasible than was the case before.
The extra radiator cooling surfaces compared to the Barcelona car are not necessarily inherent to the new layout, given that the ambient temperature in Bahrain is considerably greater than in Barcelona.
We await with great interest to see if the performance change is as dramatic as the visual impact of the new Mercedes.
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