Week9
- 1. Aerodynamics analysis around a car by CFD Hayato Suzuki
- 2. Forecast Recently, automobile industry started utilizing computer simulations like CFD(Computational Fluid Dynamics) to develop and design car body. Previously, it prepared actual car body model, and it evaluated car body aerodynamic character by running wind tunnel test. To prepare actual car body model takes time and cost. Therefore, it tended to decrease wind tunnel test and increase computer simulation. But, to re-enact actual car running had difficulty in CFD, and it had some problems like computational result accuracy.
- 3. Outline I use an open source simulation software which name is OpenFOAM. Here is how to simulate. First, I get the 3D data of a car. I can not make whole car body 3D model on my own. So I get it from web. Next, I decide a size of virtual wind tunnel and position of car model in it. After that, I generate some grids for calculation, it is called “mesh”. Next, I set boundary condition like inlet of air flow. After that, I execute a simulation. Finally, I display a result by visualize software called “paraView” after finished simulation. It can display stream line, cut by X or Y or Z axis, and so on.
- 4. Motivation and Problem Statement Past CFD were a lot of simulations when a car running straight line, but they were not so real. First, a car model is not real. For example, it is too simple, its appearance like box. Or, it has only car body, no tires. My car model is normal sedan car. Second, my simulation software is open source and free software. It name is OpenFOAM. Past business engagement simulation software are too expensive. OpenFOAM was made possible simple simulation of student level like me. Finally, I use k-omegaSST turbulent model. It is hybrid turbulent model k-epsilon and k-omega. Past CFD were a lot of standard k- epsilon model. It can calculate quickly. But, accuracy is not so good. K-omegaSST can realize more good accuracy.
- 5. Methods First, creating a model data. Creating 3D or 2D model by CAD data. This model will be simulation objective. Second, mesh generation. CFD expresses calculational space in mesh. This number of mesh is very important for accuracy. A lot of mesh provide good accuracy, but it needs long calculation time. So I must find good balance. Third, running calculation. My laboratory has super computer. In CFD, calculation time is very long. So I need high spec computer. Finally, visualization. Calculation result is difficult for human eyes to understand.
- 6. Results Pressure around a car. High pressure is looked front of car. But low pressure is looked over a car. It is negative pressure.
- 7. Results This is air stream line graphic. It is not easy for us to understand. So I will fix it.
- 8. Summary From CFD simulation, I can look air flow around a car. And, I can find high pressure point around a car. Additional, I want to calculate drag force and lift force. They are important for aerodynamics. I will write them on my thesis. But, this is low quality simulation. To save time, I reduce mesh numbers. So I want to do more high quality simulation. Two graphics shows air flow and pressure around a car. But they are not easy to understand. So I will fix graphics to post it on my thesis.