Thursday, January 03, 2019

Formula One and Electro-Aerodynamics

Most travelling Formula One engineers probably think that an 'ionic wind' is the result of over-indulgence at the end-of-season curry night. On the contrary, in late 2018 a group of researchers from MIT published a paper in Nature detailing how an ionic wind was used for the first-ever flight of a heavier-than-air, self-propelled device with no mechanical moving parts.

The ionic wind was created by generating an ionic cascade between the paired elements in an array of high-voltage electrodes. Each positive electrode was a 0.2mm stainless-steel wire supported in front of a wing-section. The corresponding negative electrode was a thin layer of aluminium foil on the downstream wing-section. The ions are accelerated in the electric field, and impart some of their momentum to the ambient air-flow, thereby generating a forward thrust, (and in this case, presumably, some lift).

Ultra-light power-sources were used: a custom-made 600W battery, and a custom-made High-Voltage Power Converter (HVPC), yielding a DC voltage of ~40kV. The battery weighed only 230g, and the HVPC weighed 510g.

The thrust generated by the experimental device was ~3N, from a wing-span of 5.14m, so the thrust itself isn't about to grab the attention of the Formula One community. However, one might instead be tempted to re-task such ionic wind devices with accelerating the boundary layer flow in certain areas, enabling one to avoid separation at moments of extremis.
Ionic wind accelerating the flow at the bottom of the boundary layer. (From 'Ionic winds for locally enhanced cooling', Go, Garimella, Fisher & Mongia, Journal of Applied Physics 102, 2007). This retards separation by delaying the point at which the slope of the velocity profile, at the wall, becomes zero.
Plasma-actuators for boundary layer control have been under aeronautical development for some years, and unfortunately their use in Formula One seems to have already been proscribed. The Technical Working Group notes for December 2006 contain a request for clarification on the issue from James Allison, and in response Charlie Whiting declares that he had "already given a negative opinion, based on moving parts influencing the car's aerodynamics."

This is a slightly puzzling response, because the whole point about plasma actuators and ionic winds is that they involve no moving mechanical parts. The objects in motion are electrical currents, and the ambient airflow itself, both of which are considered to be consistent with the regulations, and indeed necessary for the function of a Formula One car.

So perhaps there's a future here for electro-aerodynamics in Formula One. It would be an exciting line of research, and one which might also be considered beneficial to Formula One's environmental credentials.  

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