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STAR-CCM+: FS/FSAE Resources and Suggestions

[ Edited ]

RESOURCES:

 

Our FSAE technical resource guide is a great place to start. It covers tutorials and example cases on a wide variety of applications in addition to FAQ articles. Some of those example cases include:

–External / Internal Car Aerodynamics

–External Car Aerodynamics Cornering

–2D Dual Element Wing

–3D Dual Element Wing

–3D Dual Element Wing Shape Optimization

–Exhaust Manifold Conjugate Heat Transfer and Thermal Stress

–Intake Manifold Coupled with 1D Engine Code

–Modeling Valve Motion and Closure Using Overset Mesh Zero Gap Interfaces

–Fuel Tank Sloshing

–Brake Cooling Internal Duct

–Radiator

–Heat Shield (Thermal Radiation)

–Automation: Angle of Attack Sweep

 

 

SUGGESTIONS:

First I would like to note that these recommendations are based off my own experience in collaborating with FSAE teams.

 

Validation

Most of the material here is focused on designing the car. However, if you have wind tunnel data for your car it’s always a great idea to simulate the same car in STAR-CCM+ and compare the results to the wind tunnel data. This will allow you to iteratively refine the setup of your 3D simulations to ensure you have the best setup in STAR-CCM+ for future simulations. If you do not have this data you will need to use the best practices we outline for you.

 

Design exploration in 2D

Starting with 2D is a great way to get started with CFD. Since the front wing determines how the flow behaves downstream,  it will affect the side pods, undertray, rear wing, etc. So starting with a 2D simulation of the front wing is a great way to figure out the general shape (horizontal/vertical stretching), position, and AoA your front wing elements should be. You can also include the simple shape of an undertray/diffuser to determine the best ground clearance, general shape, and relations between the front wing and the undertray positioning.

 

How do you do this? Choose an airfoil profile to use, there are many online resources to help you find the correct high DF/D (or -L/D) profile for your team. This is just a starting point for your airfoil profiles though. After the following process is used, custom profiles can be developed for each airfoil since a scaling parameter can be used to stretch or compress the size of each airfoil in the vertical and horizontal directions.

 

Start in STAR-CCM+ by importing your car body so you can ensure your wings and undertray are positioned/sized correctly. You may also want to import a few blocks which will help to show you the limits of where your geometry can move in X, Y, and Z . Create a simple sketch for your undertray. Something like a three point spline curve on the bottom and a straight line for the top (with the upstream and downstream points being coincident). Create a point where the gro. is located, right click and anchor it. Set a vertical distance from this point to the and expose a design parameter from this point to the undertray inlet, middle, and back (diffuser). See the following article for more information on design parameters: https://steve.cd-adapco.com/articles/en_US/FAQ/AR-3-194

Create a transform sketch plane for your each wing, import a 3D curves for each wing, extrude the profile, and scale the wing in X and Y. See: https://steve.cd-adapco.com/articles/en_US/Video/Creation-of-Wing-CAD-Parameterized-for-Rapid-CFD-De...

Build/run your simulation, use this:

https://steve.cd-adapco.com/articles/en_US/FAQ/Class-Supplements-for-CFD-Fluids-and-Heat-Transfer-Co...

Go back to the geometry level, change the design parameters as needed, click mesh, click run. Repeat. Note that if you would like to automate this process and use an algorithm to search the design space, this is a great place to get started with optimization. For more information on how to approach this, see our optimization sections here:

https://community.plm.automation.siemens.com/t5/Formula-Student-Forum/bd-p/FS

 

Pros of 2D:

2D runs much faster than 3D.

Because of this, you can refine the mesh further without making the runtime impractically long. This means you can investigate smaller features on your car like gurney flaps and control arm fairings. It also allows you to see trends and general flow features.

 

Cons of 2D:

The exact values in 2D simulations results will not match realistic force values for a real FSAE wing because of the assumptions made in 2D modeling. These assumptions limit it’s application. For example: It doesn’t make sense to make a 2D simulation on an intake manifold, which is highly three dimensional in its geometry and flow features.

 

 

Design exploration in 3D

Next start on 3D. Design your car from the front to the back. Just start with the front wing and other components on the car immediately downstream of it that you want to start designing. Use the results (the best AoA, position, etc) from your 2D simulation to build your front wing (perform some simple extrudes). Then include any new features that you may need such as end plates. Include the car body, tires, undertray, and side pods. You need to optimize these systems first so don’t include the driver, rear wings, control rods, etc. It’s also best not to go overboard on including small/detailed features such as the wheel rims, steering wheel, etc. Focus on the features that will impact the design the most first.

 

The CAD to mesh process if very important, I highly recommend reviewing this:

https://community.plm.automation.siemens.com/t5/Formula-Student-Forum/STAR-CCM-How-to-test-more-desi...

 

After running your initial simulations of the front wing, undertray, and side pods -- use the existing simulation and add the back wings and driver. Follow the same procedure outlined before to parameterize the back wing. The focus of here should be to reach the desired forces for the rear wing while at the same time ensuring the center of pressure for the car is in the right location. From here you may want to explore adding additional features such as the control arms, interior of tires, etc to see what other smaller design improvements you can make.