Editor: ChongLei Zhao
Hydroplaning is the phenomena, in which frictional force diminishes between rolling tire and road surface, when a vehicle drives on a wet road covered by water film. The water collides with the tire leading edge and drains through the circumferential and lateral grooves of the tire tread, while giving rise the hydrodynamic pressure and deforming the tire. As a result, the water flow and the tire dynamic deformation in the tire hydroplaning is strongly interacted to each other through the complex tire tread surface.
The picture below is a schematic representation of the three zone concept (Moore, 1975; Hays and Browne, 1974) which classifies the region between the tire and wet road into three distinct parts: the hydrodynamic region A (tire is fully floated), the viscous hydrodynamic region B (tire is partially floated), and the complete contact region C (tire attaches to the road directly). It is worth noting that the occurrence of individual regions depends on the water depth and the tire velocity. For instance, we can see from the picture that when tire rolling speed is 75km/h, the footprint diminishes significantly, which means that the frictional force diminishes.
More specifically about the three zone concept, in region A, water collides with the tire leading edge at given speed so that the kinetic energy of water changes to the hydrodynamic pressure. As a result, the tire is deformed and the wedge of water flow penetrates into the tire contact patch, and furthermore the tire starts floating on the ground once the hydrodynamic force exceeds the tire contact force. In region B considered as a transition stage from contact to floating, the tire slips on the very thin water film because the tire speed is not high enough to generate the hydrodynamic pressure to lift the tire. Contrary to region A dominated by the hydrodynamic pressure, region B is dominated by the viscous effect of water. In region C, no water film exists and tire adhere to the road completely. When a vehicle drives at low speed, region C dominates the contact patch. As the vehicle velocity increases, dynamical pressure of water tends to lift the tire and region A becomes dominant.
> FSI numerical method
Split numerical method is used for 2-way coupling deformation equations and fluid motion equations. Exchange of information between Abaqus and FlowVision takes place at specified by the user time intervals Θn+1 (FSI time step), Θn+1=Tn+1-Tn , where Tn+1 and Tn are time moments of synchronization between both solutions. Inside each FSI time step both codes can do several (or one) time increments. In present implementation an explicit splitting algorithm is used. The disadvantage of explicit method can be use of small FSI time step. But this disadvantage is compensated by fast calculation speed as not internal iterations are necessary.
> Tire pattern model - hybrid pattern
In this case, we use a truck bus radial (TBR) tire sized of 385/65R22.5 to carry out the simulation. The finite element model of pattern is modeled totally according to the real-world pattern type as shown below.
> Finite element model
The FE models of the pattern and the tire body are generated independently and connected to each other by a tied contact capability in Abaqus. Using this modeling method, we can easily replace the type of pattern without changing the main body which can help us to study the influence of tire pattern to hydroplaning behavior.
> CFD simulation model
• Tire rolling speed: 70km/h
• Initial condition: water is moving towards the rolling tire at the speed of 19.444m/s
The motion of water film when tire is rolling across it. The depth of water is 12mm
Influence of the depth of water film to tire hydroplaning behavior
Visualized results of the distribution of pressure field in water film
Visualized results of the distribution of velocity in water film
Comparison of lifting force