UPDATE #8 - January 23, 1998
We have some fun things coming up. Maybe you can squeeze them into your lesson planner! Chat with Mina Cappuccio who is planning a test on the propulsion airframe integration for the high speed civil transport- the airliner of the future! January 26, 1998 from 12 - 1 PM Pacific time. Read her bio at http://quest.arc.nasa.gov/aero/team/cappuccio.html To attend chats you register by filling out a form online to ensure a reservation. (So far there's been plenty of room in our chats!) To register go to http://quest.arc.nasa.gov/aero/chats/#chatting On Thursday, January 29, 1998 10 - 11:30 PM Pacific a live lecture and Web chat with the "Aerodynamics in Sports Technology" Project Research Team http://quest.arc.nasa.gov/ltc/special/cislunar/ On Thursday, February 5, 1998 at 9-10:30 AM Pacific We are planning a live event with Brent Wellman. There will be real media (streaming video and audio) over the Internet and Brent will demonstrate some discrepant events about generating lift with odd shaped airfoils. These tricks can be easily duplicated in your classroom!This broadcast will last 45 minutes and be followed by a Web chat. Check Special Events early next week for a link to information about attending this one time live event. http://quest.arc.nasa.gov/aero/events
Has your class been doing some airplane drawings or flying paper planes lately? Send us photos, jpegs or gifs. We can post them on the Aerospace Team Web site in the Kids' Corner under the Student Gallery. Rumor has it that kids like to see their work on the web. http://quest.arc.nasa.gov/aero/kids/
[Editor's Note: Robyn Gottheiner is a high school intern at Ames Research Center and as part of her experience she interviewed Mina Cappuccio, Aerospace Engineer. Robyn made a Web page about Wind Tunnels at http://quest.arc.nasa.gov/aero/teachers/windtunnels.html]
A DAY IN THE WIND TUNNELS
January 23, 1998
As a senior at Palo Alto High School, I had the option of taking a class called Science Research. This class places students with a mentor who works in a field that interests the student. I chose to study at NASA with Susan Lee who works on the Aerospace Team Online Web Site.
One opportunity Susan provided me with was to visit with Mina Cappuccio. Mina deals with models of high speed planes, and she tests them in the wind tunnels.
My visit with Mina turned into an amazing educational experience. Not only did I learn about such terms as Reynolds Number and what functions each Wind Tunnel specializes in, but I got the chance to see two of the many wind tunnels at Ames!
The wind tunnels at NASA have always intrigued me. As a child I would always stare at the huge building with amazement as I passed by on Highway 101. I would fantasize about what went on inside these wind tunnels. I pictured researchers in big space suits calculating information as they watched some mind-blowing spectacle.
Well, to tell you the truth, I wasn't too far off (except for the space suits!). As we entered the 11 by 11 foot Transonic Wind Tunnel, Mina unlocked the safety door that leads to the main floor. (Transonic means that the air inside the tunnel can travel at speeds that range from high subsonic to low supersonic speeds.) The huge room had a large cylinder-shaped object that stretched the whole length of the room. Mina explained that the tunnel went in a circular shape, and that we were only looking at a small portion of the Wind Tunnel. I didn't understand why this huge facility was called "11 by 11 foot". But quickly, it was brought to my attention that this dimension referred to the height and width of the tunnel where the model is placed (this piece of the tunnel is called the "test section"). So, basically, the model of the airplane that they are testing has to fit in an 11 by 11 foot area.
The reason they chose this dimension for this Transonic Wind Tunnel is so the researchers can study the model at Mach numbers between 0.4 -1.5, at a Reynolds Number of 1.26 -9.4 x 106 per foot. I learned that each Wind Tunnel specializes in different Mach and Reynolds Number ranges, densities, pressures, forces, and many other conditions. So, the model is placed in a sturdy holder that is downstream from the model (this is so the holder doesn't interfere with the airflow around the model). The standing air is pushed through the circuit using a very large compressor with the model in the test section of the circuit.
The researchers sit in a room near by, where they watch the model on many video screens and calculate really important information for improving the plane (or whatever the company is building). It is necessary for the technicians and researchers to be in a separate room because of safety precautions. If there was a crack or mishap in the tunnel, people could potentially be sucked into the Wind Tunnel. This is why these tests in the Wind Tunnel tend to be limited to people involved in each experiment.
After seeing the 11 by 11 foot Transonic Wind Tunnel, Mina took me to see the 9 by 7 foot Supersonic Wind Tunnel (Supersonic means that the air travels at speeds faster than sound). The area the model sits in this tunnel is obviously much smaller than the previous tunnel. This Wind Tunnel also deals with higher Mach Numbers, lower Reynolds Numbers, a different range of pressures, and many other conditions. Mina explained that this, as well as other Wind Tunnels in the NASA facility, were temporarily out of use because they were being equipped with high tech computers for data, and the actual tunnels were being repaired too. She said that they were originally built in the 1950's and that NASA hoped to reopen these Wind Tunnels for tests within the next few years.
Because the Wind Tunnels are being repaired, this means that Mina and other researchers have to travel to other places to test in Wind Tunnels. I was surprised to learn that there are tons of other Wind Tunnels all throughout the country. But, the biggest in the world is right at NASA Ames in Mountain View!
Even though I didn't visit the biggest Wind Tunnel, I still feel privileged to have had the opportunity of seeing two smaller tunnels. I learned a huge amount about the purpose of Wind Tunnels and how they help technology. I hope that I have been able to relay some of the exciting and educational information that I encountered in this adventure.
As I continue to work with NASA until the end of the school year, I am learning one really big lesson. The basics that students are taught in school, like Physics and Math, are the keys to all the interesting technological work at NASA and all over the world. I have been able to value what I learn in school, because I know almost all the theories and calculations will be applied in whatever I do later in life.
ONE WEEK TO GO! - FLOW VISUALIZATION
By Fanny Zuniga
January 14, 1998 This week the test team and I are busy trying to solve a new mystery. The balance has been calibrated and it looks good. But when we plugged the balance into our computer we didn't get a very good signal. There are some electrical components between the balance and the computer (like amplifiers and signal conditioners) and we don't know where the problem is yet. The big worry is that we can't do a final check of the balance with our computer until we've solved this problem. Some of our team members from Boeing are showing up here this week, so with the extra help we should still be able to start our test on time. We are supposed to start putting our model in the tunnel on January 20. At that point the model, balance, instrumentation, and software have to be ready. On another front, the software group chose this week to make a major upgrade to the wind tunnel software. This means the people who were working on my test's particular software are busy. Some of the calculations I want in our software may not be available until after our test starts. Also, we found those accelerometers I mentioned before, but now we can't find the cables and power supplies. If it isn't one thing, it's another. Lastly, we are also refining our plans and preparations for using those techniques I mentioned before which help us understand how the air flows around the model. You may recall I mentioned one way we were going to do this is with colored oil that flows on our wings while the tunnel runs. The problem with oil is that we can only get a picture of the airflow for a few conditions because it takes so much effort and time. The other methods of "flow visualization" we will use are tuft photos and Pressure Sensitive Paint, so I want to describe them for you. This week we decided when in the test we would use these different methods. The first method is to put really fine threads, or tufts, all over the model. These tufts are so fine that they don't change the airflow on the model, but they do show which way the air is going. We take a picture in Ultraviolet light (UV, or Black Light) because the tufts are florescent. We have to use high powered UV strobe lights so that we can "freeze" the tufts because they tend to wiggle a bit (the airflow in our tunnel is not perfectly steady) and we don't want a blurry image. So all we have to do is mount special UV strobe lights above a clear window in the top of the test section and take pictures. What's neat about this is we don't have to stop the tunnel and reapply oil for each condition we want to study, if the airflow changes at a new model attitude or tunnel speed, we just take another picture. It takes time to stick the tufts on the model and install the cameras, but after that we can get a lot of information without slowing down our test too much. The other method we plan to use is to paint the model with Pressure Sensitive Paint, or PSP. This is a neat method of recording pressures on the surface of the wings. Basically, we use a special paint that glows in UV light. How bright it glows depends on the air pressure. We take video images of the painted model using UV lights in the top of the test section, and then process the images with a computer. PSP is a lot like using the tufts, it takes time to paint the model and install the cameras, but after that we don't have to stop the tunnel and repaint it for each condition like we do with the oil. After it is applied, the paint for PSP only lasts for a few weeks before it ages and quits working. We are using one more method to understand the aerodynamics of our model. You see, one problem we have is that the wings bend, or deform, slightly under high lift loads. What this means is that the shape of our model will actually change slightly with different loads and conditions. This means it is hard to compare Lift and Drag from one condition to another because the model itself has changed. We use a neat video system, mounted in a side window of the tunnel, which records images of some reflective spots on the wing tip and then computes how much the wing is bending and twisting. So, the big decision we had to make this week was when we would conduct the oil flow study, and when we would paint the model for PSP. Yes, we are still refining our run schedule! We decided to put both of these activities near the end of the test. Basically, we want to put things that are either risky or time consuming near the back of the test so that we can assure we collect our most important data (like Lift and Drag force measurements) first. As I mentioned, the oil flow photos are time consuming. As for PSP, since the paint doesn't last very long we have to paint inside the tunnel in the middle of our test. The tradeoff here is that after we paint the model we have to change the model back to some configurations we will have already tested. If we painted the model during the first week, say, then we could get PSP information anytime during the test until the paint got old. Then we'd have to repaint it which takes more time.
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