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Formula SAE Race Vehicle Bodykit 2D Simulation

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Old   August 26, 2009, 00:54
Arrow Formula SAE Race Vehicle Bodykit 2D Simulation
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Matt
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Hi everyone,

I'm currently doing my thesis project on the 2D CFD simulation of a Formula SAE race vehicle body kit using Gambit/Fluent. I've got the body (with diffuser) geometry and mesh sorted, but now I'm trying incorporate a rear spoiler. I've attached screenshots of the comp. domain and proposed spoiler location. You can see from the picture that I have left the face above the body unmeshed to insert the spoiler.

To determine the airfoil's geometry I plan on using the airfoil profile generator at:

http://www.ppart.de/aerodynamics/profiles/NACA4.html

Just wondering if anybody has any tips/advice on how I can efficiently (and as accurately as possible) insert and mesh the spoiler?

Any help would be greatly appreciated!

Thanks,
Matt
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File Type: jpg body_comp_domainZOOM_location.jpg (45.7 KB, 41 views)
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Old   August 26, 2009, 08:20
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Andrew
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are you trying to mesh the spoiler or the fluid around the spoiler? What exactly are you looking for?
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Old   August 26, 2009, 09:30
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Meshing the fluid around the spoiler is my main concern. Right now I'm looking at inserting the spoiler geometry (where the red circle is in above pic), making an ellipse around the spoiler and meshing the spoiler to the ellipse (as shown in attached pic) and then meshing the ellipse to the outer face (outlined in red in second attached pic).

Comments on that??
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File Type: jpg body_comp_domain_location.jpg (42.6 KB, 25 views)
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Old   August 26, 2009, 09:37
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I think I would combine the geometry so it was one 2-d image, and then mesh everything at once. The best way I have found to do this is to draw the 2-d image in something like Solidworks and then import it into gambit. That way you will be able to define the F1 image as a wall and do one mesh for the fluid around it. Again, it depends on what you are looking for to whether or not you will want a finer mesh at certain areas.
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Old   August 27, 2009, 09:15
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Thanks for the advice Andrew, I'm meshing the geometry at the moment, I'll let you know how it turns out.

Also, I have another (novice) question, once I've run the simulations, how do I display aerodynamic characteristics such as Lift/Drag coefficients etc?
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Old   August 27, 2009, 09:35
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I am not sure if Fluent can give you the lift/drag coefficients, but what it can give you is the velocity at specific points in your geometry. So, you might have to crunch that out yourself. Again, I am not sure if it will spit out the lift/drag - it might. You'll just have to dive into it. Also, the tutorials are really good. Your professor should be able to log onto Fluent's website and download the tutorials.
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Old   August 27, 2009, 10:26
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No worries, I'll give manually calculating the lift/drag coeff's a shot.

I have access to the tutorials, and you're right, they are very good, but I haven't come across and instructions on displaying lift/drag coefficients, if anyone else could point me in the right direction that would be great!!
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Old   August 28, 2009, 00:07
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Okay, so I've figure out how to find the lift/drag coefficients. I set two force monitors (lift & drag) and ran the simulation producing two graphs containing the converged solutions of the lift/drag coeff's.

However, I can only roughly determine the converged coeff's (by tracing the line back to the y-axis value). How do I get Fluent to display the exact accurate converged solution for these graphs? I've attached the graphs.
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File Type: jpg NACA4412_quad_cd_plot.jpg (36.6 KB, 16 views)
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Old   August 31, 2009, 09:52
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Hi matchoo,

In the Force Monitors dialog in Fluent there is an option to write the output of the Lift and Drag of selected walls into a file. Use this option to get the values at each iteration.

Andy
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Old   August 31, 2009, 13:21
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Like Andy said, export that graph data... you could bring it into MS Excel if you like that format better (I know I do). There still may be a tad of variation between iterations so you could just pull an average from that converged part of the data (say the last 500 timesteps) to get the final number.
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Old   September 2, 2009, 19:02
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You can also report the forces acting on any desired region. Fluent will list pressure and viscous forces as well as coefficients. You will want to look at the total coefficient value on the end.

One thing to remember is that fluent will base these coefficient values on the set constants. You can change the values to match your model.
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