Wind Tunnel Tests

03/23/17


In some wind tunnel tests, flow visualization techniques are used to provide diagnostic information. Visualization techniques include free stream smoke, laser sheet, or surface oil flow. The assumption is made that the flow visualization medium moves exactly with the flow. Shadow-graphs or schlierin systems are used to visualize the shape and location of shock waves in compressible flows. For low speed flows, tufts or surface oil indicate the flow direction along the surface of a model.(This is the method that I will use to test my models as it is the most practical one.)

In some wind tunnel tests, the model is instrumented to provide diagnostic information about the flow of air around the model. Diagnostic instrumentation includes static pressure taps, total pressure rakes, laser Doppler velocimetry, and hot-wire velocity probes. A diagnostic test does not provide overall aircraft performance, but helps the engineer to better understand how the fluid moves around and through the model. There are a variety of flow control devices that are employed to improve performance of the aircraft, if the local flow conditions are known. Depending on the type of instrumentation used in the experiment, steady state flow or unsteady, time-varying, flow information can be obtained. The engineer must use some experience when employing flow diagnostic instrumentation to properly place the instruments in regions of flow gradients or separations.

In some wind tunnel tests, the model is instrumented with pressure taps and the component performance is calculated from the pressure data. Total pressure measurement is the normal procedure for determining aircraft inlet performance. Theoretically, the aerodynamic force on an aircraft model could be obtained using pressure instrumentation by integrating the pressure times an incremental area around the entire surface of the model. But, in practice, pressure integration is not used because of the large number of taps necessary to accurately resolve pressure variations. Airfoil drag can be determined by integrating the total pressure deficit in the wake created by a wing model.

In some wind tunnel tests, the aerodynamic forces and moments on the model are measured directly. The model is mounted in the tunnel on a special machine called a force balance. The output from the balance is a signal that is related to the forces and moments on the model. Balances can be used to measure both the lift and drag forces. The balance must be calibrated against a known value of the force before, and sometimes during, the test.

Gas Section

03/22/17

I still have not gotten the materials yet for this section, but at the end of the post I listed what I need so you guys get a glimpse of the materials that I will be using in order to make this section.This step is essential to the tunnel since you need some kind of indicator to be able to see the approximate wind flow. The single most important tip I would give is to use dry ice and warm water if you have access to it.  The purpose of the water is to speed up the process of creating smoke since the cooler the temperature of the system, the less likely the ice wants to sublimate into CO2 gas.  It is also cleaner and doesn't clog up the tubing as much.  Only downside is that you need a water catcher under the tubing when the cold air condenses inside the tubing creating water.

~Materials
-Jar w/ lid
-Hand pump of some kind
-1+ ft of Airline tubing (fish tank)
-Hot Glue/ Water tight sealant
-Incense / Dry Ice + warm water

~Tools
-Drill w/ right bit for the tubing and pump head to fit into

Almost Finished

03/09/17

This post is going to be talking about the progress I have made onto my wind tunnel so far this week.

I am almost done with the wind tunnel as I have to just install the gas section and spray paint the whole wind tunnel in the colors of the space center. I talked to my on-site mentor, Jon Van de Water, and we are still  uncertain on whether we are going to use this one as a display or make another wind tunnel based off of this one. This wind tunnel turned out pretty good and we can still use it to test objects, so we are in a dilemma right now. If we decide to use this one then my work on making wind tunnels will be done and I can start to focus on making the display for the center which incorporates the wind tunnel. Otherwise, I have to help make another wind tunnel then focus on making a display which is just a lot of work as it took me about five weeks to just finish one out of cardboard. Another one with better material might take longer and I don't have that much time so we might just use this one in the display. I will get a lot of help on the other wind tunnel though as I would be working on it with people who work at the center. They used to be engineers so maybe it would be finished pretty quickly, but who knows exactly how long it would take. This is pretty much it for now and look down below for pics and videos showing how the wind tunnel looks right now.

How does it work?

03/02/17

Wind tunnels are used by engineers to test the aerodynamics of many objects, from jet wings to car windshields. Aerodynamics as a science studies the flow of air or gases around an object in motion. With a better understanding of the way air moves around (or through) objects, manufacturers can devise and create faster, safer, more reliable and more efficient products of all kinds.

Wind tunnels are simply hollow tubes; at one end, they have powerful fans that create a flow of air inside the tunnel. Some tunnels are desktop-sized and good for testing only very small objects. Other tunnels are massive structures in which engineers test full-size aircraft and cars. Although the test materials (usually) remain stationary, rapid airflow inside the tunnel makes it seem as though objects are moving.

Typically, there are sensors and instruments inside wind tunnels that give scientists hard data regarding an object's interaction with wind. And often, there are windows that let those same scientists observe experiments visually. With those data and observations, engineers grapple with variables of aerodynamics such as pressure, velocity, temperature and density. They gauge lift, drag, shockwaves and other conditions that affect planes and other contraptions that speed through the wind. In addition, these tunnels can help engineers figure out how wind interacts with stationary objects, such as buildings and bridges, and find ways to make them stronger and safer.

Measuring airflow is tricky as air is invisible, so how do you see whether a plane is performing well or badly inside the tunnel? There are three main ways. You can use a smoke gun to color the airstream white, then watch how the smoke shifts and swirls as it passes the plane. You can take what's called a Schlieren photograph, which makes variations in the air speed and pressure show up so you can see them. Or you can use anemometers (air-speed measuring instruments) to measure how fast the wind is going at different points around the plane. Armed with your measurements and lots of complex aerodynamic formulas, you can figure out how good or bad your plane is and whether it would really stay up in the sky.

Progress

03/01/17


This week so far has been really exciting as I am seeing it all come together. I am almost finished with the wind tunnel and it doesn't look that bad for my first time. I just need to finish the last section, the diffuser, then I am done. I already cut out the parts of cardboard for that section its just that I have to tape them all together. After that I need to install a gas section on top of the wind tunnel so that we can see the wind's effects on whatever we are testing.

Besides building the wind tunnel, I also take part in many activities at the center. I am learning more about the aerospace industry everyday as I am talking to people who work at Raytheon or Boeing which are some big aerospace companies. I have learned a lot about aerospace engineering by talking to many engineers who work at those companies as they tell me what they do on a day to day basis and how the job actually is. They tell me a lot about being an aerospace engineer like the problems they face and how they handle it. I am just happy that I am gaining a lot of experience here on my field of interest which is going to benefit me in the future. Everyone at the center has been really helpful as they check on me everyday and see my progress.
They are all so experienced at what they do so each conversation I have with them is like its own seminar on the aerospace industry. Its also cool to see that the center has many connections with NASA which is where I want to work eventually. I might even get to talk to some people at NASA in the near future which excites me the most as I have so many questions for the aerospace engineers who work there. These connections that I am making with various aerospace industry specialists has really been informative and helpful.

Schools from all over the Phoenix area take field trips here daily and sometimes I get to help the staff coordinate the field trips. The kids participate in these space missions and hypothetical scenarios in space. They also get to take part in various space simulations like the "Voyage to Mars" where the time frame of this mission is sometime in the not-too-distant future, when humans have established a permanent base on Mars. Crew members will serve as the first crew on Mars and the relief crew en route to the planet. While on the Martian surface, the team will have collected and analyzed a great number of planetary samples and data. This information is vital to scientists for a better understanding of the planet Mars. Crew members also will have gained an appreciation for the "luxuries" of planet Earth such as air, water and food as compared to a barren planet such as Mars.

These types of missions are for everyone and I have a lot of fun helping the kids out with these missions and other activities. Everyday I do something different like build my wind tunnel, help with the field trips, talk to people from the aerospace industry, or even help with the normal tours around the center. Overall, I am just really happy that I found the perfect internship for me that correlates with what I want to do in the future and I know for a fact that all these experiences and connections that I am making are going to definitely benefit me in the future.