How was the CierzScience Tunnel project born

The idea of this tunnel came to not having neither project nor tutor of thesis at the end of my career as aeronautical engineer. After having tried to develop a project proposed by a professor at the University and know that he was far above my knowledge , I decided to be I who chose the project and as I develop it.

My first idea was to build something physical related to my career and that it could be used in the future and not to be forgotten and useless, in the act I thought to build a wind tunnel.

After a brief search on the Internet I had an idea of how it would be my tunnel, but I note that, although there were many projects like that I wanted to make, there was nobody who had detailed step-by-step how to build a wind tunnel. In one they give you an idea of how to make the body or an idea of how to develop the electronic or the measurement of forces, but none so complete.

So I decided that my project was to build the most complete possible wind tunnel, and then be able to share it with the community. Even if the result will not be perfect and that it should be go refined, I hope that will serve as a basis or guide to someone who want to repeat it enter the changes that it seems that enhance the design.

At the same time I thought in the design I thought also in the name of the project. My city, Zaragoza, is characterized by a strong wind called cierzo and I wanted to make it a tribute and end up calling the project: CierzScience Tunnel .

How to design our own wind tunnel

To design our own wind tunnel, the first thing that we need to assess is the complexity that we want to give to the project that will have an impact on the quality of the results of the tests that we make in him. Second, the maximum size of the objects that we want to study that will have an impact on the size of the testing chamber and therefore in the rest of the tunnel. Third the speed of the air that we want to reach in the test chamber.

There are basically two types of wind tunnel depending on the air circulation in its interior, closed or open. With the first we have conditions thermodynamic stable and the study would be more precise but will be of a building more complex and take a larger space. With the second we will not have conditions thermodynamic as stable although the complexity of its construction and the space that deal will be lower. In this case we decided the second configuration. With regard to the other types of configurations we chose testing chamber closed, air aspirated and of course subsonic.

Our tunnel is thought, in the beginning, like a basically didactic tool that should allow us to visualize the flow lines about a body and to measure on him the forces to which it is submitted. The size that we think that it would be the correct one would be one that was occupying a volume of about 15 cubic cm. Later these bodies can be extrapolated to others of major size.

To carry out the design we have to predefine a speed of the air inside the test chamber that would allow us to carry out the studies. The speed of 70 km/h would be a speed that would allow us to realize them. To perform the calculations take the speed of 20 m/s.

In the case of the construction of the CierzScience Tunnel the first thing that we acquired was the fan of second hand that conformed to the features that we were looking for. The air flow that moved, its size, the structure on which was mounted and the price were the ideals for our project.

From the diameter of the structure of the air output of the blower, the flow rate that offers us the fan, the speed in the test chamber and the volume of the object of study, we will design the rest of the tunnel.

The flow that offers the fan is 8400 m3/h, 2.33 m3/s. Its section we estimate from the radio. Being the radius 0.25 m, the area of its section is of 0.196 m2.

Knowing that the flow is the result of the product of the speed and the section:

Q = S(2)*V(2) ; V(2) = Q/S(2) = 2,33/0,196...