Monthly Archives: November 2012

Single Element Wing

We are also working on a single element static wing.  I would like it to be ready to be prototyped by the beginning on the new year.  The profile was designed by using a a program written by myself in Matlab using the panel method.

CFD Model of Single Element Wing

CFD is currently being used to improve endplate design and to find optimum location of the wing on the FRS.  Location of the wing will dictate the wing mount design.

Pressure Cut Plot on Rear Wing

The blue color under the wing dictates areas of low pressure.  Looking at the top side of the wing, red/orange/yellow can be seen.  This shows areas of higher pressure.  As you can tell, there is more low pressure created than high pressure.  The underside of the wing is where the magic happens!

Pressure Surface Plot on Car and Velocity cut Plot

This plot shows how the wing reacts to its surrounding. What is the point of designing a great wing but not implement it to its application?  This is why we analyze the complete application.

-Paul

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CFD Software

The CFD (computational fluid dynamic) software we use is OpenFOAM which is an open source finite volume discretization scheme CFD package built on C++ library used primarily to create applications. OpenFOAM can solve just about anything with its 50+ pre-built solvers. In addition to its standard solvers, OpenFOAM’s friendly syntax lends itself to easy creation of custom solvers.  OpenFOAM is normally runs on a Linux machine, and we use Ubuntu as our Linux operating system.

Ubuntu Screen

Solved Case Folder

Mesh creation in OpenFOAM is done using two utilities.  We use blockMesh for the creation of the “windtunnel” test section.  This is the fluid area around the car.  The mesh for the vehicle comes from snappyHexMesh which generates 3D hexahedra and split-hexahedra from a surface geometry.

Surface Mesh on the Scion FRS

Close up of Surface Mesh

To solve, I normally use a steady state incompressible solver with a k-omega SST turbulence model.  I might go into more details at some point if there is interest.

 To collect data on improvements, I have the solver calculate the coefficients of lift and drag along with the aerodynamic balance.  This allows actual calculation of downforce and drag in pounds.  The aerodynamic balance helps with total vehicle design and is very very important.

The post processing (pretty pictures) is done with the use of Paraview. Paraview is very powerful and a great tool to use.  I use Paraview on Windows because it is much more stable than on Ubuntu.

Screen Shot of Paraview

Now why do we use OpenFOAM?  This question is very easy to answer.  OpenFOAM allows unlimited customization to meet our needs.  I can change the solvers and/or write my own codes.  It is a proven software with users all over the world.

-Paul

Picking Charities Part 2: Earth

We at Hancha are a collective of nerds, so, it’s easy for us to be awed by NASA and space exploration; but, it does not mean we have forgotten about Earth.  Cars have a bad reputation for being dirty and are a symbol of pollution, but in reality less than 15% of all CO2 emissions come from road vehicles.

Just because we enjoy burning petrol, doesn’t mean we don’t care about the planet.  It doesn’t mean we should stop trying to reduce that amount and reduce our environmental impact.  In the meantime, what we can do is offset our CO2 emissions by increasing photosynthesis and increasing the CO2 to Oxygen conversion.  That is why we have chosen to support Cool Earth in preserving rainforests.  Each year we will donate part of our net profits to preserve enough land so we have a net Oxygen output.

Picking Charities Part 1: Space

I believe we are extremely fortunate and privileged to do what we enjoy.  I also believe we should give back to the world that’s been so good to us.  The issue dearest to my heart is promoting education in the STEM majors (Science, Technology, Engineering, and Math).  However, I believe the best way to do that is by helping fund NASA, a technological juggernaut which promotes advancement for all mankind.  So, I am proud to announce we will be donating a portion of our net profits to Penny4NASA each year.

People may believe that spending money for the exploration of space, when we have problems here on Earth, is a gross misuse of money.  However, it is estimated for every dollar spent by NASA, there is a return of ten dollars in the economy, making it one of the best investments.  We use things created by NASA every day, things like velcro.

Space exploration also unites us as humans. When Neil Armstrong landed on the moon, it may have been the single most significant event for us as a people.  It did not matter who you were, where you were from, and what you believed; we were united under the moon, knowing one of us was walking on it.  It spawned a generation of new scientists and engineers armed with the dream of exploring the corners of the universe.

– Earl

These videos highlight the wise words of Neil deGrasse Tyson and does an excellent job summing up the influence of space exploration.  I highly recommend viewing them.

New Workstation

Image

Thanks to the Student Innovation Fund our workstation has finally arrived.  It’s a Dell Precision T7600 workstation with an Intel Dual Four Core Xeon processor, 64GB of DDR3 RAM, and a 1TB hard drive.  This includes a commercially licensed version of Creo Parametric 2.0 and will be setup with a virtual machine and remote desktop access so we can install OpenFoam and CADNexus so we can run CFD iterations 24/7.

FR-S CFD

Paul had done some CFD work for the FR-S to get a baseline result.  The model does have a flat floor, so the coefficients are not 100% representative to the real car since the underside of most vehicles resemble very rough surfaces.  This effect however can be theoretically determined to have a maximum total decrease of the drag coefficient of 0.045 according to R. Buchheim [1].

The results show the coefficient of drag is 0.262, close the OEM rating of 0.29.  Using the theoretical data from the smoothed underside, the coefficient of drag we calculated is valid. The coefficient of lift is .179, meaning the car does generate lift in its stock form.

[1]  Buchhiem, R., Leie, B., Luckoff, H-J., “Der neue Audi-100-Ein Beispiel fur konsequente aerodynamishce Personenwagen-Entwicklung,” ATZ, Vol. 85, 1983, pp419-425.