Teaching How to Use the CFD Approach by an Example: Hydrodynamics Within a Passenger Car Compartment in Motion

Abstract

The CDF methodology is applied to the study of the air flow around a 2-D car and its interaction with the cabin internal air. The flow visualization or computational works enable engineers to calculate different car characteristics like drag coefficient, external and internal air flow patterns, etc. Therefore, the teaching of this approach to student is a very important task to take into account in the formation process of new engineers. This work shows the numerical simulation of a specific passenger car compartment configuration solving the Navier-Stokes equations along with the k-e turbulence model using the finite volume method. The indoor air flow is produced by the interaction between the cabin inner air with the external flow through two glass windows (one in the front seat and one in the back seat). This configuration represents a common situation for the passenger car compartment. The study covers two different car speeds, 50 and 100 km/h. The flow field is studied in both steady state and transient conditions with time step of 0.01 s, for both car speeds, 50 km/h and 100 km/h. The different steps of the CFD work are commented to show to the reader the distinct states that must be cover in this kind of work. As results of the detailed methodology followed, the influence of the domain size on the flow fields is highlighted, the requirement of a better mesh quality is exposed and flow field results are analyzed using two different forms of graphic representations. The results show the physics behavior of the flow and the presence of flow structures, as for instance, indoor air recirculation zones delimited by internal seats, as well as, the vortex presence at the back of the cabin.Keywords: CFD teaching, Flow visualization, recirculation zones. INTRODUCTIONThe constant increases of costs of doing experimental tests for many industrial applications impulses the developed of computational means or CFD to characterize new designs. The computational tools solve the governing flow equations, Navier Stokes equation and continuity, throughout a computational domain, which represents the geometric characteristics of the physical space of the problem studied, that allows obtaining the flow fields relevant to the phenomenon, as for instance velocity, pressure, temperature, turbulence or electricity fields. Therefore, it is possible to achieve the characterization of the different designs in relatively low cost and time. The output of the computational work is the visualization of the whole phenomenon or part of it, based on the premises and specific objectives of the study.The aim of this work is to use the study the air flow within a passenger car compartment when it is in motion with two of the glass windows opened as an example of the application of a CFD tool. The model selected is a simplified version of the cabin with two open windows, which is built based on prismatic shapes that are usually of the most interest in others areas of applications, such as, flow around buildings, towers and bridge decks....

How opening windows and other measures decrease virus concentration in a moving car

“…(2007) studied the complex airflow inside a bus with open windows and investigated the air flow speed and pathways. Polanco et al. (2009) studied both internal and external air flow patterns of a car with a fixed window configuration and two different moving speeds.…”

“…Kale et al (2007) studied the complex airflow inside a bus with open windows and investigated the air flow speed and pathways. Polanco et al (2009) studied both internal and external air flow patterns of a car with a fixed window configuration and two different moving speeds. Ibrahim and Mehta (2018) analysed effective AC inside the rear passenger area and proposed an air depression design that optimises the air flow and temperature in a small car cabin.…”