1 What is CFD and why use it?

CFD is a technique that solves the equations of fluid motion for a given domain, such as the surface of a car or the air around it. By using CFD, you can visualize and analyze how the air flows over and around your vehicle model, and how it affects the drag, lift, pressure, and turbulence. CFD can help you identify and optimize the critical areas of your design, such as the front bumper, the rear spoiler, the wheel wells, and the underbody. CFD can also help you compare different design options and test various scenarios, such as different speeds, angles, and wind conditions.

2 How to prepare your vehicle model for CFD?

Before you can run a CFD simulation, you need to prepare your vehicle model for the analysis. This involves creating a 3D geometry of your vehicle, either through a CAD software or by importing an existing model. After that, you should simplify and clean the geometry, removing any unnecessary details that might cause meshing problems or increase the computational cost. Additionally, you need to define the boundaries and regions of the domain, such as the inlet, outlet, symmetry planes, and walls. Lastly, you should generate a mesh which is a discretization of the domain into small cells or elements that will be used to solve the fluid equations. The quality and density of the mesh will affect both the accuracy and speed of the simulation.

3 How to set up and run a CFD simulation?

After you have prepared your vehicle model, you need to set up and run the CFD simulation. This requires several steps, such as choosing a solver and turbulence model that will determine how the fluid equations are solved and turbulent effects are modeled. It is important to define the boundary conditions and initial conditions, which specify the fluid properties and flow parameters, such as velocity, pressure, temperature, and density at the boundaries and inside the domain. Additionally, you must run the simulation by iterating the fluid equations until a converged solution is reached. To ensure that the simulation is valid and reliable, you should monitor the results by checking residuals, forces, coefficients, and convergence history.

4 How to visualize and analyze the CFD results?

After you have run the CFD simulation, you need to visualize and analyze the results. This involves using various tools and techniques to view the flow field, such as contours, vectors, streamlines, and iso-surfaces, to display the distribution and direction of the flow variables. You should also evaluate the aerodynamic performance by using plots, charts, tables, and reports to calculate and compare the aerodynamic forces and coefficients. Lastly, you can identify improvement areas by using sensitivity analysis, optimization, and parametric studies to find and modify the design parameters that affect the aerodynamic performance and airflow.

5 How to validate and verify the CFD results?

Once you have visualized and analyzed the CFD results, you need to validate and verify the results. This involves comparing the CFD results with experimental data, such as wind tunnel measurements or road tests, to assess accuracy and consistency. You should also consider potential sources of error and uncertainty, such as model simplification, mesh quality, solver settings, or measurement errors. Additionally, it’s important to run a grid independence study with different mesh sizes and resolutions to check the sensitivity and convergence of the solution. If the solution changes significantly with the mesh refinement, it’s necessary to improve or refine the mesh. Lastly, a sensitivity analysis should be performed by running simulations with different solver settings and turbulence models to determine robustness and stability of the solution. If the solution changes significantly with the solver settings or turbulence models, changes or improvements should be made.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?