Vehicle Underbody Structural Performance Prediction During Waterfording Events Using A One Way Coupled CFD-CAE Approach

Water fording events are one of the most challenging situations that vehicles undergo during their lifetime. During these events the underbody components (e.g. Front fascia, Bellypan, wheel liner etc.) are subject to very high loads. Typically, vehicle water fording tests are performed for various depths of water at prescribed vehicle speeds. Water fording tests are usually carried out during the proto phase of the vehicle development program to ensure acceptable performance. If issues are discovered, making changes to the fascia or body panels are typically very expensive. To avoid late changes, a fully virtual methodology was developed to facilitate vehicle water fording performance. The simulation is targeted to evaluate multiple aspects such as air induction system and estimation of hydrodynamic loads on body panel components. This paper describes the approach for coupling CFD (Computational Fluid Dynamics) and CAE (Computer Aided Engineering) to evaluate the stress levels in the body panels and structural components during water fording tests. This study considers that the vehicle is moving through a flat road covered with water at various depths. The CFD simulation uses a commercially available RANS (Reynolds-averaged Navier-Stokes) based software to provide steady state pressure loads for CAE simulation. The CAE models use these pressure loads to compute stress and deflection of the underbody components using a nonlinear CAE solver. This coupled simulation approach has reduced the turnaround times and provided design directions to the product team early in the development cycle.