Underhood and Underbody Studies in a Full Vehicle Model Using Different Approaches to Model Fan and Predict Recirculation

This paper discusses flow through the front end of a vehicle comprising all the underhood/underbody components. Two approaches used to model the fan to predict the front-end airflow in a full vehicle model using Computational Fluid Dynamics (CFD) are presented. The approaches discussed here are the Moving Reference Frame (MRF) model and the fan plane model. Both cold and hot flow conditions are carried out for the full vehicle model. This paper also outlines the determination of fan performance curves numerically. The data from the fan performance curves thus obtained can be used in a fan plane model. The paper also discusses two methods to determine the recirculation factor in front-end flow studies namely, the user-defined scalar (UDS) method and the heat balance method. In UDS method, the amount of air recirculating into the condenser inlet from the radiator outlet is computed using a user-defined scalar and solving for it and alternately in the case of hot flow, heat balance method is used for the same. The commercial CFD package Fluent [1] is used for the numerical simulations.