How to replicate a realistic Reynolds number for an airfoil

[MattH150197]

Homework Statement

Hi I am doing a project of designing and testing a wing in a wind tunnel, the wing is based a cessna 172 skyhawk wing and I am trying to determine what chord length it should be to try and replicate similar reynolds numbers that a cessna 172 wing would experience in real life.

Homework Equations

https://www.physicsforums.com/file:///C:/Users/stc263/AppData/Local/Temp/msohtmlclip1/01/clip_image002.png

The Attempt at a Solution

I found that at 8000 ft the reynolds number ranges from 2 - 5.4 million Re for the aircraft, i found temp and pressure in wind tunnel to get density 1.24. I then put 5.4 million = 1.24*40(max wind tunnel speed) * L / 1.81x10^-5 (dyn viscosity) and worked out for L but i got a value of 1.8 m which is too big for my average chord length. Can anyone see that I am doing something wrong or can suggest how i can produce more similar reynolds numbers for the airfoil. Thanks

 

[KataKoniK]

Hello there,

As a fellow scientist, I would suggest considering the following factors in your design and testing process:

1. The type of wind tunnel you are using: Depending on the type of wind tunnel (closed circuit or open circuit), the Reynolds number may vary. Make sure to check the specifications of your wind tunnel and adjust your calculations accordingly.

2. The airfoil shape: The Cessna 172 wing has a unique airfoil shape that contributes to its Reynolds number. Make sure to carefully design and replicate the airfoil shape in your wind tunnel model.

3. Boundary layer effects: In real-life scenarios, the airflow over the wing is affected by the boundary layer, which can significantly impact the Reynolds number. Consider incorporating boundary layer effects in your wind tunnel design to get more accurate results.

4. Other variables: Apart from air density and viscosity, there may be other variables that can affect the Reynolds number, such as air temperature and humidity. Make sure to account for these variables in your calculations.

I hope these suggestions help you in your project. Good luck!