Bridge Aerodynamics Project Ideas

[Gordy]

I am in sort of a critical bind:
I've been working for several months on an ISEF entry as part of a class (actually, working on the project IS the class), and in the past week it has completely fallen apart -- I won't go into details, but there is absolutely nowhere I can take the project. However; I can't drop the class. Whether or not the project actually does well in ISEF, I still need to have an entry in order to pass the class.

SO. I have found a new general area, Bridge Aerodynamics, in which I want to start a new project, but here's the catch: I need to have experimentation up and running in about two weeks, or less. I have access to an extremely well-equipped wind tunnel at the University of Kentucky (they have already agreed to let me use it) and a LOT of spare time, but I am still wracking my brains trying to come up with the actual project.

Can anyone recommend to me some way to narrow in on a project? Or some previously performed experiment that I could use as a springboard, possibly modifying or improving on old research? I am willing to put in a serious amount of work on this, I don't want bare minimum here and I'd really like to make it impressive, but I hope it could remain within some reasonable parameter of difficulty (high school senior).

 

[Cyrus]

Two weeks?
You should have stayed on top of your project tasks. How are you going to test your model to make sure it doesn't break apart in the wind tunnel and damage the test facility? How have you scaled your model for Re number? Man - oh-man, if this were the real world you'd be so fired. Seriously, learn from this experience because outside of school that would be very, very bad.

What does your test matrix look like?

What is the aim of your results to prove?

Jeez...ahaaha. You really screwed the pooch. You have not even done background research.

You typically meet with the wind tunnel personnel two weeks before testing begins to go over final checks.

 

[xxChrisxx]

Well that really depends on the level (complexity) required from the project. There must be a broad aim.

 

[Vale-46]

I'm unsure how long this would take you to do in a lab, but it might be something to check out.

Instead of bridge aerodynamics, get some experimental data on bridges completely submerged with water flowing past (like when you get flooding over a bridge). In a search of papers in this area, it looks like there is next to no experimental data to be used to validate any computer simulations that are being done.

I've got a friend that is a Civil Engineer that deals with this issue as he works in Darwin, Australia which has a wet /monsoon season so some of the bridges he designs have to deal with this, but it sounds like there is little in the literature to help him.

I can get you in touch with my friend to give you some tips/starting points if you like.

 

[Gordy]

Two weeks? You're screwed man - sorry.

As I see it, I have a really decent amount of time: I've got about seven spare hours every day after school (not even counting weekends), all of which I'm willing to devote to this, and I don't need to be DONE in two weeks, I just need to start EXPERIMENTING and running wind tunnel tests in two weeks. I focus easily, so I'm fully prepared to devote myself to this.

As far as complexity goes, I'm looking for like an 8 (on a 1-10 scale).

I have a LOT of resources (building supplies, cash, macgyver-like ingenuity) and a lot of free time (senior year, already admitted to my universities so I don't need to bother with extracurriculars any more, and the friends have agreed to give me a while off so I can do this project). Plus, I have an entire class period every day to work and research, and the school is willing to write off nominal project expenses (if they can keep the materials once I'm finished).

Anybody? Any interesting wind/bridge-based phenomena that I could center a project around?

Last year, a student taking the same class I'm in this year had a project based on laser-based vortex detection, and I could certainly incorporate that. Not sure of the specifics of his project, but I could have them up here tomorrow after school.

 

[Cyrus]

No, you don't see my edit.

How big is this wind tunnel?

If you get anything above an C on this project, consider yourself lucky. Honestly, my jaw hit the floor reading this thread. How much time were you given to work on this?

 

[Gordy]

bridges completely submerged with water flowing past (like when you get flooding over a bridge)...

...Darwin, Australia which has a wet /monsoon season so some of the bridges he designs have to deal with this, but it sounds like there is little in the literature to help him.

Wow, that is actually a really awesome idea, I might like to run with that. In fact, the university I'm accessing DOES have a liquid wind tunnel (not exactly sure of the nomenclature).

Before I get too wrapped up in it though (which is what went wrong in my last project) can you think of any interesting phenomena he has to deal with?

 

[Cyrus]

Wow, that is actually a really awesome idea, I might like to run with that. In fact, the university I'm accessing DOES have a liquid wind tunnel (not exactly sure of the nomenclature).

Before I get too wrapped up in it though (which is what went wrong in my last project) can you think of any interesting phenomena he has to deal with?

<face palm>

 

[Gordy]

No, you don't see my edit.

How big is this wind tunnel?

If you get anything above an C on this project, consider yourself lucky. Honestly, my jaw hit the floor reading this thread. How much time were you given to work on this?

No, I understand that I absolutely screwed the pooch. I did some pretty unspeakable things to the pooch, and you can bet your life savings that I've learned from this...

The wind tunnel is about six feet square

 

[Cyrus]

No, I understand that I absolutely screwed the pooch. I did some pretty unspeakable things to the pooch, and you can bet your life savings that I've learned from this...

The wind tunnel is about six feet square

Keep in mind just because its a 'wind tunnel' does not mean it can measure anything you throw inside of it. You need to have an estimate of what forces you expect to generate, and if the tunnel balance can detect it accurately or not, or if its too large for the tunnel to handle.

Also, what kind of wall interaction effects do you expect? I.e what is the model span to tunnel span ratio.

How are you going to connect your model to the balance?

You need to meet with the tunnel engineers tomorrow and find out exactly what needs to be done.

 

[Gordy]

How much time were you given to work on this?

That's too embarrassing to answer. Seriously. I would be out on the street if this were the real world.

It's not that I was screwing around, the project I was working on (spin-casting parabolic mirrors) was pretty decent, but I kept hitting dead end after dead end and eventually I realized the entire thing had turned to crap.

I was working with my teacher the entire time, he saw how hard I was working so he said he'll be lenient on whatever I can scrape together.

 

[Cyrus]

Well, deal with what you got and move forward at this point!

 

[Gordy]

what is the model span to tunnel span ratio

I don't have a model yet, that's the point -- whether I'll be testing an entire span or a cross-section depends on the project itself, which is the entire point -- I don't HAVE a project yet. I've got university libraries, cash, time, and testing space.

 

[Cyrus]

How long you got to graduate? See if you can get the professor to give you another semester to work on the project. It could turn out really well.

The answer to your post above, of course, is make the smallest (easiest/fastest) model you can get away with!

 

[Gordy]

How long you got to graduate? See if you can get the professor to give you another semester to work on the project. It could turn out really well.

The answer to your post above, of course, is make the smallest (easiest/fastest) model you can get away with!

Not a professor, a teacher -- I'm in high school, a senior. Another semester really isn't an option ;)

 

[Vale-46]

He didn't say in particular, but have a quick look at these papers - they might answer your question:
http://74.125.155.132/scholar?q=cac....com/+cfd+submerged+bridge&hl=en&as_sdt=2001"
http://74.125.155.132/scholar?q=cac...+cfd+submerged+deck+bridge&hl=en&as_sdt=2001"

 

[Gordy]

I'm in high school

And as such, what I would consider an 8 in difficulty, you (graduate/masters) would most likely consider a two or three -- I have pretty much no engineering backgound, apart from some regional bridge-building competitions (1st place, built in 16 hours) and AP Physics/Calculus

 

[Cyrus]

Not a professor, a teacher -- I'm in high school, a senior. Another semester really isn't an option ;)

Ahhhhhhhhhhhhhhhh. I thought you were a college junior or senior. In that case, don't worry. You'll be fine! :)

Learn as much as you can when you are the WT and ask them to show you everything that goes on there.

 

[Gordy]

when you are the WT

*ahem*

Anyways, I'm interested in possibly working on a project involving the Tacoma Narrows Bridge (the black-and-white video of the bridge that looks like it's made of rubber, everyone's seen it). http://www.ketchum.org/billah/Billah-Scanlan.pdf" attributes that flutter to a specific vortex caused by the bridge's design. It's a really interesting topic that doesn't seem to go too far above my head (I understand everything apart from the actual computations), but I'm not sure how I can wrangle a project out of it.

Again, I have no background in computational fluid mechanics, or anything of the sort, but I'm definitely going for more than a baking soda-vinegar volcano here.

 

[xxChrisxx]

Anyways, I'm interested in possibly working on a project involving the Tacoma Narrows Bridge

I was acutally waiting for this to come up, it was simply inevitable. Any discussion on bridged inclused a Tacoma bridge video clip.

 

[Vale-46]

I was acutally waiting for this to come up, it was simply inevitable.

Lol. We got shown the videos across multiple subjects with every professor seeming to think they were the first ones to show it to us.

 

[Gordy]

I know, I really don't need to see it again. The point is that it still isn't fully understood, so it's a possible working area for me. Does anyone else have suggestions?

 

[xxChrisxx]

Going back to earlier, to suggest a suitable project we need to know the aims.

So for example, is it an investigative project? Do you have to try something and see what happens. Is it a demonstration project, so you know what will happen you need to gather data and explain why?

You should have at least been given a vague specification for the goals you have to achieve. They will not be related to anyone project but will outline what you have to do.

The Tacoma collapse if fully understood amongst civil engineers. You can't realistically gain anything useful from trying to recreat the circumstances and discover why it collaped in 2 weeks at a high school level. You are aiming at a level of detail not possilbe the complete in 2 weeks to any level of accuracy.

 

[Gordy]

Going back to earlier, to suggest a suitable project we need to know the aims.

So for example, is it an investigative project? Do you have to try something and see what happens. Is it a demonstration project, so you know what will happen you need to gather data and explain why?

You should have at least been given a vague specification for the goals you have to achieve.

No, no specifications, just a research project with data gained from experimentation, they're pretty much the most broad guidelines humanly possible. Yes, I'm going to be presenting it, so I need a hypothesis. Seriously, it doesn't get much more broad than this. I'll take just about anything.

 

[xxChrisxx]

No, no specifications, just a research project with data gained from experimentation, they're pretty much the most broad guidelines humanly possible.

I know the type of thing, the aims for the markers are to see if you can design a fair experiment and conduct it in a wat that you get meaningful results. You are basically demonstrating that you can think analytically and critically about something.

Always remember this, don't be overly ambitious. Abition is good but you need to know your limits and time constraints. A simple to medium difficulty project done very well will always be better than a very hard project done badly.

As an engineer part of what I do is to make an assesment of the maximum level of complexity of a simulation/experiemnt possible given the time/budget/manpower/skill set constraints.

 

[Gordy]

Ambition is good but you need to know your limits and time constraints. A simple to medium difficulty project done very well will always be better than a very hard project done badly.

As an engineer part of what I do is to make an assessment of the maximum level of complexity of a simulation/experiment possible given the time/budget/manpower/skill set constraints.

Yes, this is exactly what I learned from my previous failure (oh, yeah, I can learn fluid mechanics in a couple months, I'll just work REAL hard. No, did not work.)

 

[Gordy]

You are basically demonstrating that you can think analytically and critically about something.

And this is an area in which I really excel, so I'm just looking for a way to demonstrate it. Even just re-creating a previously done experiment would suffice (not plagiarism, of course, I'd specifically say that I was re-creating it)

 

[Gordy]

Once I can actually figure out a topic, I know that I'll enjoy moving forward with it, but this is just the most agonizing part.

 

[Cyrus]

You could look at how various bridge loadings affect the aerodynamics. Empty bridge vs bridge full of morning bumper to bumper traffic.

Or, you could vary the spacing of cables on a bridge.

 

[Gordy]

A few hours of The Google has given me a thought: Investigating air flow over bridge structures using Schlieren photography. Feasible?

 

[Cyrus]

Schlieren is used when you have density variations in the flow. For what you are trying to do, you won't get any clean pictures. For flow viz of this type, you would typically use propylene glycol and a wand.

 

[Gordy]

Is that (propylene glycol) a road I can practically move down, or does it get really complex really quickly?

And wouldn't the compression caused by the stream hitting the bridge components affect the air's density? All of the Schlieren imaging I have seen has been heated-based, so of course I'm skeptical.

 

[Cyrus]

Is that a road I can practically move down, or does it get really complex really quickly?

Easy as dirt. They should have a smoke wand for you to use at the tunnel. When you call them up tomorrow just ask.

 

[Gordy]

Fabulous, seriously (Good God, thank you Cyrus). Now, I have three possible directions to move (At least, that's how I see it):

1. Place multiple common types of bridge span in wind tunnel, observe how they interact with flow, and isolate features in each that contribute to stability. (Possibly combine into new span design?)

2. Choose only one span type and observe how different weight distributions/traffic presences affect flow (This might lead to some interesting places involving controlling traffic flow during wind events instead of shutting a bridge down altogether, but that seems doubtful)

3. Work with modifying the actual imaging method (?)

 

[FredGarvin]

Smoke wands and tassels are most likely all you're going to get. Like Cyrus mentioned, low speed stuff will not show up well in other forms of imaging because you don't get very large density differences (plus it is time consuming and pricey to set up). If the tunnel has it, you may ask about high speed video. That can be very helpful, especially when looking at wakes.

The thing that is going to eat up a lot of time is your proof that your model is not going to harm the tunnel at the flows you expect. In some cases I have worked, we had to design for a case that was not even physically possible. Again, this is another point to bring up with the tunnel folks.

Do you have to stick with bridges? That seems like a tough model to make accurately. Can you switch it to something easier like smoke stacks? Then you could really get into shape variations easily and you could see real Von Karman vortex shedding in action.