Test The Limits

Cut down grime with more digital time

By Exa

November 12 2015

No car will stay clean, especially at this time of the year, but some cars unfortunately get filthy more quickly than others. So how do you figure out whether a new model is going to attract dirt in the design stages of car development? The simple answer is you can’t, not until you’ve done road miles in a prototype; and one without all the camouflage cladding.


The difficulty is that by this stage of design the manufacturer has frozen the body and has already spent millions on creating stamping tools. It’s too late to make changes to the body surfacing, so now the only way of curing your soiling problem is to improvise. One manufacturer ended up having to put an unsightly piece of plastic on the edge of the rear wheel arch of their SUV, to change the wake interaction of the soiling – much to the design team’s dismay.


It’s not just about unsightly streaks of dirt on the flanks. Nowadays, cameras and sensors are a fundamental part of a car’s safety performance, and keeping them clean is equally essential. Not all of them can be positioned behind glass within the sweep of the windscreen or rear wipers.


Aerodynamic simulations can be a great help, but only if they accurately depict what’s happening on the road. Particles flows behave according to transient, turbulent flow effects, and accurate simulation of the airflow and particle trajectories is crucial.


Exa PowerFLOW does just that, enabling engineers to calculate how the turbulent vortices interact with the car and evolve around it, and accurately predict how dirt particles will behave. The visualization tool within PowerFLOW brings this work to life, enhancing the analytical process and providing insights into the simulation results which engineers need to understand and help improve the design.


What’s more, PowerFLOW can provide this before the stamping tools are even designed, allowing for elegant fuel efficient solutions such the minor tweaks to the paneling of the 2015 Discovery Sport. Creating these innovative solutions requires and in depth understanding of how aerodynamics influences the buildup of dirt. PowerFLOW provides this understanding so that engineers can be confident their vehicle can meet performance and safety targets before the first fully detailed physical prototype is produced.


Exa aerodynamicists are constantly working to improve their knowledge of soiling in order to give PowerFLOW an even better understanding of what happens to spray kicked up by the car’s wheels. Relaying that information to manufacturers will help them achieve their goal of building a car with no dirty secrets.