Vespa CFD/3D Model

Project Description

This is a project started as part of the Dry Lake Racer: CFD (Computational Fluid Dynamics). For that User:internetscooter (a.k.a. Paul McIntosh) paid to get his scooter 3D scanned through scan-xpress.com.au in Melbourne. For this project the data is being provided free of charge under the condition that no money be made from derivative works unless, the derivative work is feed back into Vespa Labs for the benefit of all.

Information from the original CFD (Computational Fluid Dynamics) lab notes will be uploaded and one of the Vespa 3D Model datasets suitable for CFD analysis. The complete dataset contains higher resolution detail (e.g. below) as well as scans of more standard Vespa parts. Please contact paul mcintosh at internetscooter dot com if you wish to experiment on that data. This project and data would suit university students wishing to use real world data for CFD or other modelling projects.

The data is available for registered Vespa Labs users here: Vespa 3D Model

CFD Modelling

Here is an example of what can be done with the 3D Model using open source CFD tools like OpenFOAM. As the project progresses there will be OpenFOAM examples that people can download and tweak themselves.

The above shows a test run with a "real" Vespa model but a fake rider. This shows things like the front indicators contributing a lot to the aerodynamic drag, the big red areas indicate high negative pressure zones. The above was done as a test on the VPAC and MASSIVE HPC (high performance computer) clusters. Students and researchers in Victoria, Australia have access to these clusters and may wish to consider HPC projects using the Vespa data. We encourage other HPC researchers to contribute their workflows back to Vespa Labs (or provide links to publications and cite where the data came from via the url).

Research Questions

Note that the model data also includes more standard Vespa parts (rather than the race adapted version shown). Here are some research questions that would be good to answer using this data:

1. What is the aerodyamic drag of a Vespa?
2. What is the lift force on the front of a Vespa at various speeds?
3. How much does a windscreen reduce drag?
4. What is an optimal windscreen design?
5. What is the optimal windscreen design for reduced helmet noise?
6. What is the drag impact of various sitting positions (regardless of windscreen)?
7. What are the areas on a Vespa that cause the most drag and what are the solutions for reducing drag in those areas?

See also: Aerodynamic Investigation of a Scooter in the University of Perugia Wind Tunnel Facility by Stefano Ubertini - Univ. of Rome Tor Vergata and Umberto Desideri - Univ. of Perugia.

And review (and update as needed) Aerodynamics

What's Important

Here are some bullet points on what areas of CFD to focus on for the problem of Vespa CFD (so you don't waste effort learning stuff that is not applicable)

• incompressable flow: we aren't going "that" fast so we don't need to model air compressing as part of the problem so we can just use incompressible flow models
• bluff body: we are modelling something that is not streamlined. An aircraft it streamlined so we want to know about what is happening at the surface (friction drag) but a Vespa stirs the air up so we want to know about how this causes drag (pressure drag).
• Reynolds-averaged Navier–Stokes (RANS): equations are (at the moment) the most used in this style of CFD
• Turbulence Models: are required to work out the turbulence part (since we are a bluff body this is important) e.g. RANS based turbulent models and OpenFOAM list

Additional Resources

Here are some resources that will help anyone that is learning CFD from scratch...

CFD seems to be typically taught by building on a lot of background learning, so by the time you are learning CFD at Uni you are just piecing together a number of things that you already know. If you want to learn backwards where CFD knowledge is your goal and you haven't done supporting training, then you don't know what you don't know. CFD books assume prior knowledge and won't even give a glossary of common terms that you could Google. Here is some info I have used to get some understanding. These are listed in order of required learning but you can also start at the bottom and search back up the list to find the missing bits you need as you need them.

• Khan Academy (for when you get stuck with the math)
  • http://www.khanacademy.org/#precalculus
  • http://www.khanacademy.org/#calculus
  • http://www.khanacademy.org/#differential-equations
• Math Anxiety Relief for Nearly Everyone, W. Charles Paulsen - This book will teach you calculus
• CFD Jargon: http://www.nafems.org/resources/CFDJargon/
• Mechanical - Computational Fluid Dynamics Lectures
• Aerodynamics for Students
• http://www.flow3d.com/cfd-101/cfd-101-primer.html (aimed at "free surface" liquids but still some useful info)

Some other links that I have found along the way...

• NASA's Beginner's Guide to Aerodynamics
• http://cfdrevolutions.weebly.com/cfd-course-material.html
• http://www.innovative-cfd.com/ (higher level info such as Turbulence Models)

Books

• Although this is 10 years old, the age makes it cheap and it covers CFD in the most accessible way I have found. Aerodynamics of Road Vehicles (4th Edition): From Fluid Mechanics to Vehicle Engineering ([Proceedings] / SAE)"  - Hucho, Wolf-Heinrich.'s. Heres the table of contents.
• If the maths starts making sense... I found Essential Computational Fluid Dynamics- Oleg Zikanov a good book also.