Fan Modeling in CFD Using MRF Model for Under Hood Purposes

Computational Fluid Dynamics (CFD) is today an important tool in the design process of fuel and energy efficient vehicles. Under hood Thermal Management (UTM) is one of the design fields which CFD has proven itself to be a very competitive design tool over other available tools and techniques. To simulate the under hood environment it is very important to predict cooling airflow accurately, and for this, it is very important to model all components in the cooling airflow path accurately. Important components are the heat exchangers, fan, grille-, and engine blockage. This paper has focused on CFD modeling of the fan using the most common fan model of the industry; Multiple Reference Frame (MRF). Several different aspects of this modeling strategy are examined that is of high importance to the CFD-engineer working with fan modeling. The finding of this paper is that the MRF model is highly capable of simulating fan airflow however some sensitivity are noted and documented. The model is very sensitive towards end-user working procedure. The CFD engineer working with this methodology in the under hood should be made aware of that the choice of reference frames and frozen position of the blade can have a very big impact on the simulated result.