MotoGP is now a battleground of aerodynamic supremacy as teams unlock the performance potential of intuitive airflow. Each bike on the grid has evolved into a sophisticated blend of aerodynamic wings, profiles and fairings.
Unlike other motorsport categories, aerodynamics arrived in MotoGP relatively late in 2016, as a tactic for increasing load on the front axle to minimise the risk of wheelies. But in 2021, aerodynamics re-emerged as Ducati pioneered a ground effect diffuser fairing, which sparked an intense development race that has continued ever since.
The Challenges Of MotoGP Bike Aerodynamics
Motorcycles are an aerodynamicists nightmare. The bluff body of the rider, along with many components are exposed. This combined with two rotating tyres and the rapid switching of directions as riders lean into corners, results in highly turbulent and fluctuating flows. Teams try to manage these chaotic flow structures by using aerofoils, reducing drag and optimising the balance of aerodynamic forces on components.
As well as streamlining flows, another tactic to a fast lap is to maximise downforce in the corners. The greatest lap time gains come from faster cornering as a higher corner exit speed carries through to the following straight, accumulating more lap time savings overall. However, to achieve this, more downforce needs to be generated in the corners to increase grip and allow higher cornering speeds.
Ground Effect Gains
One of the most effective ways to create downforce is to exploit ground effect, which is why we have seen a surge of these devices entering the sport. In fact, at the 2023 Sepang Grand Prix all five factory outfits arrived with ground effect devices for the first time in MotoGP.
Aprilia Racing developed an alternative. This used the shape of a fairing at maximum lean to create a Venturi tunnel, rather than using inlets.
These fairings are mounted on the front underbody on either side of the bike and extend rearwards in a convex shape. During high-speed corners when the bike is at full lean, the outer surface of the fairing on the leaning side is parallel to the ground, creating a narrow channel of air between the fairing and the ground. This channel widens towards the rear due to the fairings convex shape, forming a Venturi tunnel which expands the air as it flows rearwards.
The Venturi effect accelerates the flow through the channel, decreasing pressure. This pressure difference between the low-pressure air in the narrow channel and the high-pressure air in the expanded section sucks the bike towards the ground, increasing downforce. Subsequently, grip increases, allowing the bike to corner at higher speeds.
Transforming MotoGP Aero With CFD
Alongside these fairings, Aprilia have also pioneered rear spoilers, blown diffusers and aerodynamic leathers to maximise the aerodynamics of their MotoGP bike. All of which were developed through CFD software such as HELYX.
CFD is a powerful tool to reduce the cost and time of aerodynamic development, which is why teams such as Aprilia try to simulate everything in CFD before testing parts in the wind tunnel. With such turbulent flows in Moto GP, the CFD models must be extremely accurate to capture all the interactions of the airflow. For example, the rider is the main component of any simulation, so modelling the finer details such as the roughness of clothing and features on the helmet become vital.
Although with so many different geometries to analyse in a short period of time, Aprilia needed CFD software that significantly reduced the computational time of simulations, whilst retaining this high level of accuracy. Through using HELYX’s coupled solver, the Italian team can now run simulations 2.5 times faster than before, allowing them to complete many more simulations per day.
How HELYX Delivers Performance On Track
Coupled Solver Stability
The HELYX coupled solver is a numerical approach which solves the velocity and pressure equations simultaneously across the domain. Whereas the more conventional segregated solver method solves the equations separately for each variable. By resolving the equation simultaneously, the coupled scheme requires more computing power and memory for a single iteration, and therefore takes longer to run than the segregated solver. However, it converges faster and is much more stable.
Another benefit is the automatic meshing capability of HELYX. By meshing almost any geometry effectively, less time is spent checking and refining the mesh. This, combined with the coupled scheme and its stability has enabled Aprilia to run more simulations per day and have confidence in their results.
Intuitive Dictionary Structure
To optimize the design of aerodynamic devices for different rider positions, lean angles and speeds, Aprilia runs as many simulations as possible, which is why faster runtime is a priority. However, achieving this also requires a swift and simple setup phase, facilitated by HELYX’s intelligent dictionary structure.
When a new model is created, it can be easily integrated into Aprilia’s automated system because the necessary dictionaries are simply copy and pasted. For example, an incompressible model can be quickly changed to compressible by copying one dictionary, a few kilobytes in size. Furthermore, the open-source nature of HELYX makes it scalable, so Aprilia can simulate as much as they want without running into license problems. Of course, the ideal solution for any race team is to simulate everything, but this is impossible with current resources and budgets. Consequently, the strategy is to simulate as much geometry as possible and optimize the aerodynamics for a variety of conditions quickly, to deliver performance on track.
Photo credit: With kind permission of Aprilia
