Sliding Mesh Fan Approach Using Open-Source Computational Fluid Dynamics to Investigate Full Vehicle Automotive Cooling Airflows

Abstract

<div class="section abstract"><div class="htmlview paragraph">Cooling airflow is an essential factor when it comes to vehicle performance and operating safety. In recent years, significant efforts have been made to maximize the flow efficiency through the heat exchangers in the under-hood compartment. Grille shutters, new fan shapes, better sealings are only some examples of innovations in this field of work.</div><div class="htmlview paragraph">Underhood cooling airflow simulations are an integral part of the vehicle development process. Especially in the early development phase, where no test data is available to verify the cooling performance of the vehicle, computational fluid dynamics simulations (CFD) can be a valuable tool to identify the lack of fan performance and to develop the appropriate strategy to achieve airflow goals through the heat exchangers.</div><div class="htmlview paragraph">For vehicles with heat exchangers in the underhood section the airflow through those components is of particular interest. Since the cooling fan is the main driver of the airflow in the underhood compartment at low vehicle speeds, its accurate modeling is a prerequisite for a higher fidelity airflow prediction.</div><div class="htmlview paragraph">In this work, some aspects of fan modeling for cooling airflow are discussed in more detail, and the most common modeling approaches are briefly outlined.</div><div class="htmlview paragraph">Furthermore, transient simulations using the sliding mesh (SM) procedure are presented that allow for a higher fidelity prediction of the flow field in the underhood compartment.</div><div class="htmlview paragraph">To determine an accurate and cost-efficient computational sliding mesh (SM) setup, detailed numerical studies of a fan in a full vehicle were performed by using different time steps on an open-source code. To prove the applicability of the proposed method for full vehicle simulations, the procedure is physically tested in a drive-cell in the Fiat Chrysler Automobiles (FCA US) facilities and the flow through the heat exchanges is compared to the result obtained by the transient sliding mesh simulation as well as to the results obtained with three classical fan models (Blade angle, fan curve and MRF model).</div></div>