IB Aerodynamics Investigation

[deleted-292375]

So, yeah...
In the IB curriculum, one of the major assignments required for all students to complete is a huge investigative essay (4000 words, experiment required for science topics) called the "extended essay." Because of my personal interest in aerospace, I decided to choose aerodynamics as my topic. However, I REALLY need assistance on pinning down a particular topic for my investigation. Thus far, I've heavily considered a focus on the effects of wing sweep upon section-flap effectiveness, but I don't know if this is either too complex or too simple. If it's too simple, what might be good to add (without turning it into something too complex for a high-schooler to plausibly do)?

[deleted-292375]

To clarify, I'm completely lost in regards to how exactly I could narrow down the focus of the idea, while still maintaining a significant level of detail to fit into 4000 words. Also, in addition, if anyone could point me towards a decent CAD software for the theoretical calculations, that'd be fantastic.

[audreyln]

As a former IB student I understand your struggle to find an appropriate focus area for an extended essay in science...

I think your proposed experiment around the effects of wing sweep on section-flap effectiveness is a good starting point. Will you be able to satisfy the experimental requirement using CAD modeling? Or would additional work be required? Your ability to test your hypothesis may limit your scope/complexity. If you get into your analysis and find it too simple I have no doubt that you will be able to find additional questions where you can drill down and focus on more complex areas. Start with your proposal and add to it as you go if necessary.

Unfortunately I don't know any CAD software - hopefully another Expert can provide some recommendations.

Good luck!

Audrey
Douglas County High School IB Class of 2003

[bfinio]

Hi,

I'm not familiar with the IB curriculum at all, so unfortunately I can't provide much help there. I do hope I can clarify what kind of software you need though. CAD = Computer Aided Design. It is used to make 2 or 3 dimensional models of things, but does not actually simulate anything on its own. To actually simulate fluid flow (to do things like calculate the lift and drag on a wing), you need Computational Fluid Dynamics (CFD) software.

Many times these two types of software do go hand-in-hand, e.g. major CAD programs will have add-on packages where you can do CFD. The two CAD programs I'm most familiar with are Solidworks (by Dassault Systems) and Invenstor (by Autodesk):

http://www.solidworks.com/

http://www.autodesk.com/products/inventor/overview

Each company has their own respective fluid flow simulation software:

http://www.solidworks.com/sw/products/s ... lation.htm

http://www.autodesk.com/products/cfd/overview

The caveat is that you usually need a pretty powerful computer to run this software, and normally it's expensive - something only big companies or universities can afford. The good thing is that I think both companies offer their software at a very steep discount or free to students. You will have to check to see what their exact policies are, but last I checked, most Autodesk software was totally free if you're a student (I think it requires registration and a valid school email address):

http://www.autodesk.com/education/free-software/all

Whereas Solidworks costs $150:

https://store.solidworks.com/studentstore/default.php

Full disclosure: Science Buddies has funding from Autodesk for some of our projects, but our projects focus more on their "apps" and not the professional software:

http://www.123dapp.com/

There's a simple wind tunnel simulation program called FlowDesign, but depending on how complicated your work is, it might not be sufficient:

http://www.autodesk.com/education/free- ... low-design

Hope that helps!

[deleted-292375]

Thank you (both) so much for your assistance. Also, if possible, can one tell me what sensory equipment would be best for this? I have a (seemingly) decent total budget of $3000 for my experimentation.

[bfinio]

That depends - what do you actually want to build and measure? Do you need to measure lift and drag on an airfoil? Are you building a wind tunnel? I actually don't really know what "effects of wing sweep upon section-flap effectiveness" means without further explanation, so it's hard to make any recommendations for the experimental setup. I do know that we have a guide on how to build a wind tunnel:

https://www.sciencebuddies.org/science- ... -toc.shtml

but another option might be to try and see if there is a local university that will let you use their existing wind tunnel for your experiments.

[deleted-292375]

Basically, the numerical value of the "sweep" of an aircraft's wing is the angle at which the wing is swept back or forward (modern airliners feature wing sweep in their design, as well as almost any modern fighter aircraft). The section-flap effectiveness is (definition is from my research) a coefficient-based value that identifies the level of effect that a given angle of flap deflection (the angle at which the flaps on the back end of the wing are tilted to) will have on the lift force. Essentially, section-flap effectiveness describes how much the flap will affect the lift force acting on the airfoil (2D cross-section of the wing). Apparently, from what I have read, the wing loses a portion of lift because the forces are now acting at an angle, rather than perpendicularly. Thus, I want to test the change in lift force and drag force at varying degrees of flap deflection (both up and down), with three different levels of wing sweep for the overall testing period (no sweep, +15" sweep, and +30" sweep; I may add more levels if necessary). I don't know whether to have this set up in a 3-D environment (wingtip is exposed; allows formation of wingtip vortices, which create induced drag as the higher and lower pressure airflows meet and create vortexes) or to set up the experiment in a 2-D environment (wing spans from wall-to-wall in a wind tunnel, preventing wing-tip vortices from forming, but I am unsure if this will negatively affect the data).

[bfinio]

Hmm - this is a pretty advanced project. Based on your description, my assumption is that wing sweep makes the problem inherently 3D because the airflow isn't perfectly parallel to the wing cross section. With a 2D problem you assume you can take a "slice" of the airfoil and all the airflow is parallel to that slice, but that isn't the case if the wing is swept forward or back. If you haven't already, I'd try googling (Google Scholar might be a better option than regular web search) to see how others have set up wind tunnel and/or simulation experiments to measure wing sweep.

[deleted-292375]

I did, and they tended to feature much larger wind tunnels. If I tweaked the design of the wind tunnel design presented on the site, I wonder if it'd be possible to perform the experiment.

[bfinio]

It's been quite a while since I took fluid dynamics, but I know there are some basic rules for making a scale model instead of testing something full-size (like making sure the Reynolds numbers are the same). If you get all that correct, I imagine you should be able to use a smaller wind tunnel.

[deleted-292375]

Thank you very much for your assistance. By essentially (in addition to minor changes in angling) increasing the overall size proportionately while also acquiring a much higher-powered fan, the reynolds number comes out to give a numerically similar, laminar-ish airflow in comparison with the wing's real life counterpart, from the Cessna 172, in its usual cruising altitude (around 5000 ft = 1524 m). Again, thank you so much for your help. By the way, in the wind tunnel schematic on the website, it mentions "wiring materials" as a necessary part. What is this, and what is it for? Connecting the induction fan to a power source (or a speed control)? Connecting the fan to a power source? Connecting the anemometer?

[bfinio]

I took a quick look through the tutorial and it looks like that is referring to the "Part C: Electrical Control Box" section on this page:

https://www.sciencebuddies.org/science- ... l#diffuser

about wiring an on/off switch for the fan. I haven't fully read the entire tutorial and I'm not sure what kind of fan you're using, but I imagine if you already have a fan with a built-in on/off switch or speed control, then this wouldn't be necessary.