I'm very happy to post here. This is where I've helped the most to build a wind tunnel. I could do it by looking at the results of many of the leading researchers here. Thank you, and I hope this wind tunnel will help those who hesitate to make it.

The most important thing in the pre-production stage is to understand the principles of the wind tunnel. If you search Google, you will get many images to help you understand. I think this layout is the fastest way to understand it.

Step 1: Materials

1.5L PET bottle

large-caliber straws

Insulated tape

Black color paper (A4 size is enough. The thickness is irrelevant.)

Styrofoam (to make airfoil, Of course, airfoil can be made of metal or other materials. Follow your plan)

Electric wires

1.5V batteries

LED strip (to lighten test section)

D.C. Motor and Propeller

2 switches

Dry ice(Got it from Baskin Robbins)

Nickel plated pins (replaceable with a needle, Needed to set up airfoil made of styrofoam.)

Box for putting the wind tunnel

Disposable plastic take-out cup

Cutter

Double-sided tape

Step 2: Create Working Section Using PET Bottle

Step 1 requires PET bottles and large-caliber straws, insulated tapes, black paper, cutter, double-sided tapes, and LED strips.

Cut the PET bottle. I used a 1.5L bottle of Milkis. Because there was no flexion and the width was constant.(I don't know if Milkis are common in your city, but it is at any mart in Korea) You can cut the size for your airfoil size. I just cut it to fit the dividing line of PET bottles. The cut is bumpy, so I put on insulated tape.

Cut large-caliber straws. I cut it to about 6cm. Each of the straws was fastened with double-sided tape.

*The straws keep the turbulence in the incoming air straight.

I bought LED strips online, but the wires and LED were separated, so I had to solder them.

Put a switch in the middle of the circuit and Connect to batteries. My LED strip is for 12V, but it's turned on enough at 9V.

Attach the LED strip to the inside of the PET bottle. It is recommended that the wires are well organized and the switch is pulled out.

Put black paper on the pet bottle. Don't put the whole thing on, just half it on. The reason for putting black paper is to see the flow of gas well.

Step 3: Make Fan With D.C. Moter

I bought the propeller in a slightly smaller size than the diameter of the PET bottle.

Insert the propeller into the motor and connect the wires. Like the LED strip, put the switch in the middle of the circuit.

I fixed the motor on a small paper cup. You can set the height to fit your PET bottle.

*Fan let the air pull through the tunnel.

Step 4: Design a Airfoil

My goal was to make a wind tunnel and study the flow of air by the angle of attack from the airfoil. So I could make one airfoil, so I just made airfoil using styrofoam simply. The shape and number of airfoil to be manufactured will vary depending on the individual's purpose of exploration. My little advice is, if you have enough time and money, make it from metal rather than Styrofoam. Styrofoam is bumpy and not very good at observing the flow of air. I put on Scotch tape to make the rough side smooth.

If you learn how to determine the shape of the airfoil, Designation of chord line, determination of camber line, determination of thickness distribution, determination of top surface, determination of same thickness distribution and bottom surface, final airfoil shape production stage, you can see that lift occurs depending on the position of the camber line. Therefore, the wind tunnel can be used to study the airfoil according to the change in the camber line.

Step 5: Ta-da!!

Attach the wind tunnel well onto the box using double-sided tape. If you plan to replace the airfoil (or the object you wish to experiment with), you should not attach the motor.

To observe the clear flow of gas, dry ice was sublimated. The disposable plastic cup was drilled to the height of the straw, and the dry ice was added and the water spilled so that sublimation could occur quickly.

Step 6: Experiment

I made a wind tunnel as part of my school project. As I said earlier, I wanted to conduct an experiment to explore the flow of air by the angle of attack from the airfoil.

More clearly than expected, the flow of the gas could be observed. It's been much simpler than planned in the very beginning, but I'm fully satisfied.

Airfoil, the investigation of fluid flow is quite interesting. I consider the greatest significance of this experiment to be "extended." You can always go to a more profound stage if you want to experiment a little more sophisticated and a little deeper. In that sense, I had the desire to further develop this experiment. I also want to study about the Lift coefficient according to the separation point of the airfoil and the angle of attack by obtaining data on the airfoil rising from zero degrees until stall attack angle exceeds.