CFD modelling of water ingestion in air intake system

The main function of an air intake system is to supply the engine with clean air. When driving during rainy conditions water may enter the system and it is desired to reduce the amount to a minimum level. This thesis presents a numerical model of how water is ingested and water film is developed in the air intake system on a vehicle driving at three different velocities. The work is done by solving the stationary air field around the complete vehicle and then releasing water droplets from an injection field in Fluent. The result is then exported to the in-house code Continuum Phase Wall film model developed in Matlab where the transient water film progression is computed. With help of CFD computations I have studied how water film progresses in the air intake system. The simulations are performed at high speed driving and detailed figures over the development and progression of water film are shown and analysed. The outcome of the simulations might explain the results received from wind tunnel experiments at Volvo. New drain modifications, based on the results from the simulations, are then presented within this report. The water film code uses the Weber criterion to determine if and when droplets will separate from the walls. The code fails with the transport of water film in some cells and accumulation of unreasonably large film height values are received. This problem is solved by implementing a second separation criterion in the code, which enforces separation in cells where the film height exceeds a specific value.Validerat; 20101217 (root