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This article looks to provide an overview on ANSYS Fluent and its tools to analyze, as well as optimize, the vehicle's aerodynamic performance.  

Prerequisites:

  • An aerobody model (solidworks, step, parasolid) which can be knitted and thickened to at least 10mm (higher is better).
  • Lots of patience and something to kill time with as ANSYS loads and solves

CFD Overview

We want to calculate what air particles are doing around our car. Essentially we are looking to build a virtual wind tunnel and shoot air at our car to see how it reacts. To do so we must:

  1. Geometry: Load our car aerobody CAD and define our wind tunnel dimensions
  2. Mesh: Build an accurate mesh that represents reality 
  3. Solution: Define parameters to solve

The Process

Steps in BLUE represent actions one would do inside ANSYS. 

ANSYS

This is ANSYS workbench. We are using ANSYS's Fluent Module to do our analysis.

Double click on "Fluid Flow "Fluent" to load the module.

The module has five parts: geometry, mesh, setup, solution and results. Each have their respective status symbol.

 Up To Date: This is what we want. It indicates the step is complete.

Unfullfilled: The previous step is incomplete and "upstream" data is missing

 Attention Required: Previous step is complete, but action needs to be taken to proceed.

Update Required: Something in a previous step was changed and the step needs to be updated.

Refresh Required: For our pruposes, its the same as update required.


So looking at our current module, we have everything unfulfilled and attention is required on the geometry step. Each cell must be Up to Date before starting the next step.

Double click geometry to open the Geometry Modeller. 

Geometry

In this step we will load in the car model and build our "wind tunnel" Additionally, since the car is symmetrical, we will slice the model and win tunnel in half and only solve for either the right of left half.

This reduces our calculation time by around half!

Click `File>Import External Geometry File", then click "Generate"

Our geometry is loaded. Time to build the wind tunnel to contain our "air".

Click "Tools>Enclosure" 

For simulation purposes the air moves around the car (as opposed to car moving thorugh air). If we want, we can model the ground to be moving as well, but that is not needed for accuracy.



Meshing

Setup/Solution

  


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