Characterisation of the flow in a water-puddle under a rolling tire with refracted PIV method

In this work, the fluid flow in a water puddle while a rolling tire crosses the puddle is studied. A measurement method adapted to track measurements under a rolling tire is developed. This method, based on PIV (Particle Image Velocimetry), is based on the refraction of the laser light sheet at the flow/window interface. This allows us to illuminate particles and record their images from a single optical access. This technique called refracted PIV (R-PIV) is characterised with a laboratory controlled experiment. When characterised, this technique is applied to in-situ measurements on the track. Measurements performed allow to highlight specific behaviours in different parts of the flow, in front of the tire and inside tire grooves in the contact patch area between the tire and the road. In front of the tire, the linear evolution of the water velocity in the puddle as a function of the vehicle speed is demonstrated. At high vehicle speed, non-linear effects are highlighted and linked to the shape of the contact patch area which evolves at high vehicle speed. Under the tire contact patch area, two main types of grooves contribute to the draining of water. Firstly, the longitudinal grooves are the straight grooves aligned with the rolling direction. In these grooves, the velocity of the fluid flow depends on the vehicle speed and also on the presence or not of the wear indicator. A secondary vortex like flow structure is also demonstrated in this work. The second type of grooves are the transverse grooves which are the grooves oriented with a certain angle compared to the car rolling direction. In these grooves, this work proved that the velocity is dependent on the groove location in the contact patch area. This seems to be linked to the tire deformation with the load of the car in the contact patch area. Finally, this work discussed the link between the different tire groove types to explain different specific behaviours.