Development of Prediction Method for Engine Compartment Water Level by Using Coupled Multibody and Fluid Dynamics

When vehicles run on the flooded road, water enters to the engine compartment and sometimes reaches the position of the air intake duct and electrical parts and causes the reliability problems. Numerical simulation is an effective tool for this phenomenon because it can not only evaluate the water level before experiment but also identify the intrusion route. Recently, the gap around the engine cooling modules tends to become smaller and the undercover tends to become bigger than before in order to enhance the vehicle performance (e.g., aerodynamics, exterior noise). Leakage tightness around the engine compartment becomes higher and causes an increase of the buoyancy force from the water. Therefore the vehicle attitude change is causing a greater impact on the water level. This paper describes the development of a water level prediction method in engine compartment while running on the flooded road by using the coupled multibody and fluid dynamics. MPS (Moving Particle Semi-implicit) method was used to analyze the free surface flow and 3-dimensional multibody dynamics analysis was applied to calculate the suspension displacement due to the hydrodynamic force. As a result, the accuracy of the prediction method was within ±5% and the time history of the water level and suspension displacement showed a good agreement with the experiment. And the results showed that the phenomenon of the water rising was categorized into 2 patterns depending on the vehicle speed and water depth. Through the discussion, the importance of considering the vehicle attitude is indicated and it is concluded that the running conditions could be categorized by regarding the force acting on the vehicle when running on the flooded road.