## 1 Introduction  
Many countries around the world have liberalized regulations on the limit values of equivalent noise level A regarding traffic noise. However, the growing interest in electric cars is going to reverse this trend. More and more often combustion engines are replaced with electric ones, which eliminates noise from the fuel combustion process. At the same time, research is conducted to minimize the tire noise. New tire designs and silent road surfaces are created. In this situation aerodynamic noise begins to play an important role in the overall noise generated by vehicles. Based on [PERSON]'s research [1], it can be observed that the aerodynamic noise begins to play a similar role to the tire noise at 120 km/h for passenger cars and 80 km/h for van vehicles. For this reason, it is important to develop techniques to study these types of phenomena. The numerical calculations are generally applicable in Mechanical Engineering. The results are received without the need to prepare high-cost measurements, where in many situations professional equipment is needed. One example is the study of aerodynamic and aeroacoustic parameters of vehicles. In that case a wind tunnel with measuring equipment is necessary. Additionally, it is required to isolate the object of research from unwanted interaction with the measuring environment, such as noise from fans or sound reflection. Computational Fluid Dynamics (CFD) responds to all of these requirements. CFD is a part of fluid mechanics that uses numerical methods to find solution for partial differential equations and approximate flow fields of fluids even for complex physical systems. For this purpose the finite-volume method is used. The issue is to prepare an appropriate mathematical and numerical model that reflects the phenomena of such a case. Many works in the automotive area present investigations into aerodynamic parameters like drag and lift coefficients or pressure distribution. This is particularly important due to the amount of fuel consumed and the generated aerodynamic downforce. More complex models are related to multi-physical phenomena. [PERSON] et al. [2] developed a numerical model of exhaust gas propagation for two passenger cars. Their paper presents the effect of turbulence caused by vehicles on the concentration of pollutants. Another example of multi-physical phenomena is presented by [PERSON] et al. [3]. Their research focused on the analysis of structure vibrations under the influence of air flow load (a truck driving under a footbridge at high speed). Often, research is also carried out on coupled phenomena, such as flow fields with temperature exchange. The study of the cooling efficiency of a radiator by air was presented by [PERSON] et al. [4]. [PERSON] et al. [5] went a step further. Their paper presents an experimental and numerical study on noise generated by axial cooling fans. The research focused on noise caused by airflow. For this purpose, the Large Eddy Simulation (LES) turbulence model and the Ffowcs Williams-Hawkings (FW-H) analogy were used. [PERSON] et al. [6] conducted a Computational AeroAcoustic (CAA) study using [PERSON]'s acoustic analogy. A bluff body was used as a geometric model in that work. A bluff body has a trapezoidal prism shape with a flat front and a 50 degrees slanted rear. Results received from a CFD simulation were used in the Ffwocs Williams-Hawkings equation to predict external aerodynamic noise. In the validation process, a CFD simulation of a cylindrical object was performed in two-dimensional space and the results were compared with available data in the literature. As the second stage of methodology validation, an experiment was performed in a wind tunnel where a bluff body was used. [PERSON] et al. [7] performed an aeroacoustic analysis of a car with a rear spoiler. In that work, an unstructured mesh was applied. A simulation of airflow around the vehicle was carried out in two stages.