When the wind blows: MIRA testing day

February 2015

As we are always keen to point out, the Rp1 has been extensively developed and engineered using computer aided design tools.

Mark, our aerodynamics expert, used the very latest CFD (computational fluid dynamics) software to develop the unique downforce generating front and rear diffusers and refine the bodyshell shapes and details. This would make the car as aerodynamically efficient as possible.

These computer simulations are great and you can do an amazing amount of work using these tools.  However when it comes to validating or fine tuning your work, there really is no substitute for doing some proper real world tests to achieve optimum results.

When our good friends at Niche Vehicle Network very kindly offered us the opportunity of a few precious hours testing the car inside a full size wind tunnel, we leapt at the chance.  Another bonus was a chance to work with a very experienced F1 Aerodynamics expert who would help guide and assist us through the testing process during the couple of precious hours we had available to us.

So, on a rather cold and overcast January day, some of the Elemental team travelled to the Motor Industry Research Centre (MIRA) near Nuneaton to get some proper data on the cars aero performance.

The car was wheeled into the centre of the windtunnel, a ‘dummy’ driver with helmet was strapped into the driver’s seat, and the team decamped into a small control room to start the test. For the initial run the car was put in an airflow that simulated 80mph road speed. Downforce was measured by comparing the weight of the car when static with the difference in when the tunnel airflow was running. Aerodynamic drag data would also be shown.

Initial figures looked good for downforce but as always, there was room for some improvement, particularly on drag which looked slightly worse than we had anticipated. Quick discussions followed and for the second test we sealed up a few gaps in the bodywork of our test car.

The next test showed obvious improvements as there was a noticeable reduction in drag and therefore aero efficiency. A flurry of questions between Mark, John, myself and our F1 expert followed. Can we change a certain area? What if we alter the feature? Can we get these ideas into the revised car design? More discussions, debates and sketches – but time was limited so we moved on to the next stage of the test.

Into the windtunnel now (with us all standing in a freezing cold 60mph gale to observe at close quarters) where we ran a smoke-stream across the car to show us how air was flowing around the car. Photos and videos taken and all the time we were coming up with more ideas on how to further improve the car.

During this phase a few things we had noticed during road and track drives were checked over, and some revised detail parts tested out in a controlled environment.  The key thing we found was that the core aerodynamic performance was working well so we had a good baseline to build from.

The final part of the session was probably the most interesting for me as it involved testing the car with Flow-Vis. You may have seen this on Formula one cars during Friday practice: it’s a fast drying, day-glo green liquid that you spray over parts of a car. Then you do an aero test so the paint runs in the airflow as it dries. Think of the effect as being the same as blowing on wet watercolour paint when you were at playschool. The result is a clear visual representation of the flow, movement and eddies of the air as it moves across the car.

Fascinating stuff. More discussions, photos and videos were taken as the test drew to a close.

The result of the day was a lot of new data that backed up our design, but also some interesting opportunities to further optimise the design of the production release.

Yellow Streak Testing, Testing…