Driving when it is raining can be a stressful experience. Having a clear unobstructed view of the vehicles and road around you under these conditions is especially important. Heavy rain conditions can however overwhelm water management devices resulting in water rivulets flowing over the vehicle's side glass. These rivulets can significantly impair the driver's ability to see the door mirror, and laterally onto junctions.
Designing water management features for vehicles is a challenging venture as testing is not normally possible until late in the design phase. Additionally traditional water management features such as grooves and channels have both undesirable design and wind noise implications. Having the ability to detect water management issues such as A-pillar overflow earlier in the design cycle is desirable to minimize the negative impact of water management features. Numerical simulation of windscreen water management is desirable for this reason.
This paper focuses on recent advances towards the goal of simulating A-pillar overflow. This includes a validation study on a Jaguar saloon, including both numerical simulations using Exa PowerFLOW™, a commercially available LatticeBoltzmann (LBM) CFD solver and experimental testing in a thermal wind tunnel. The experimental procedure, which is based on the use of UV dye and a surface release point, is described. The results at two difference vehicle speeds are then compared with those of simulation. The CFD results are then used to further investigate the mechanisms determining the point at which the A-pillar is breached. This includes a detailed investigation of the flow structures around the A-pillar and their effect on water management.
Overall the study explores the mechanism of A-pillar overflow onto the side glass and provides much-needed validation of the CFD technique for simulating this mechanism.