I hope you all are pursuing your interests and attempting to satisfy your curiosity. With many other good things, it is fun and rewarding, but can take hard work. Alright, in our wind tunnel project our next piece of construction takes us to the diffuser! Recall our general wind tunnel design (in blue), appropriately drawn on the back on an envelope, You can see the diffuser on the right of the test section, it is long and expands to larger than the fan, in order to house it:
We return to wind tunnel construction. Our extended absence in construction is unfortunate, but this is a lesson in many pursuits which are not our day job. These evening and weekend tasks often hit delays and sometimes we can’t return to them for a while. However, don’t give up. We may get discouraged and think our goals not worth attempting. Don’t believe this, have patience and return when the opportunity arises again. With diligence life often has enough little opportunities and breaks, so that after a few years of intermittent work, we can look back and be surprised at how much we’ve accomplished. So it is with basement science, and now we return to constructing the wind tunnel
Ever wonder why textbooks are so long? Well, I figured it out! Its because there is a lot of information out there to learn and it takes quite a few pieces of paper to fit it all. Well, this blog post is a little longer, though not quite textbook length, because there is a lot of information required in applying that textbook knowledge to building our wind tunnel.
Its time for another day in the lab (basement). Lets review our situation: We built the tunnel, legs for the tunnel, and finished the bell mouth including the honeycomb. Before we go on to the fan and diffuser, we can’t forget the minor detail of accessing the inside of the wind tunnel once it’s built. We must have an opening so we can put our specimens into the wind tunnel. Otherwise we would have a very fancy and long fan. I was hoping for more than that.
Here we are, placing the last finishing touches on the entrance to the wind tunnel. This is pretty exciting! We are discussing today what is known at the honeycomb. I very briefly mentioned this part of the project in Wind Tunnel Design Overview, but now we will discuss its purpose and construction.
So, if you remember, the purpose of the bell mouth entrance is to reduce all the whirly-twirly turbulence coming into the test section. Reducing this turbulence increases the accuracy and consistency of lift and drag measurements. Well, believe it or not, despite all our valiant efforts on the bell mouth, there is still turbulence in the flow. Bummer! Well, no worries because we can simply install a honeycomb to help us out (as a note, there is always some turbulence in this flow, we are just reducing it as much as possible). A honeycomb consists of lots of little tubes. These tubes kill turbulence because there can’t be big swirls in a little tube. Here is a highly technical drawing laying out the details of this complicated phenomenon:
I am sorry, but of late I have been absent. This is due to what is commonly known as moving. It was a lot of work, but now we are back.
For those concerned, I did move the wind tunnel! It required care and thought of how to pack it, but it is here and in its new location. With honesty in mind, I must admit that it is no longer in a basement. Hmm, what to do? Should I relocate to a living quarters with a basement? Should I stop investigating because I no longer have a basement to conduct it? No! I shall make do with what I have and continue in the spirit of basement science! Our name shall remain because the spirit endures. Just because our laboratory is now above ground does not change our goals or opportunities. Thanks be to God. Let’s begin again.
Wind Tunnel construction had taken a little break for our adventure into the world of interesting photos, but its time to meander back to our basements. Last time we planned the construction of the bell mouth so now we shall execute our plan. This part of the wind tunnel construction is a little more detailed oriented, which makes it more difficult, but the joy seeing it completed is even greater! There is unspeakable satisfaction when I behold on the table what I pictured in my mind.
Dear Fellows of the Basement Science Research Consortium,
For those new to the field, it is an important lesson to learn that the longer and more complicated the organization name, the more prestigious and talented the group. Therefore, we are part of a very important research group!
Our next task is to build the bell mouth. An overview of this was explained herea little earlier. I was trying to think of a good way to construct this as I was wandering though
Here we are, on to more construction. You may say, “What, I thought this was science not wood shop class!” Well, to conduct experimental science you have to build stuff. So, that is what we continue to do, building stuff to conduct our experimental science. Also remember, you have to build stuff right in order to get any good results.
Where we stand now is we have our “tunnel” and our measurement/test stand. We need to complete construction of our tunnel. Let’s now review the few basic remaining parts of a wind tunnel. Please refer to my highly technical drawing below which lays out our plan. The main drawing is in blue, the rest are a few dimensions I was working out.
This section is a lot more theory than construction, which is good because if there was no theory in this basement we couldn’t call this science.
For our force measurement we are going to use springs as discussed earlier. I explained in “Lift and Drag Measurement Gauge” a little about linear springs. But here is a little refresher. Your common daily use springs are pretty closely defined as linear springs. This means that the force exerted by the spring varies linearly with the length stretched by the springs. This idea is captured by the equation F=-k*x. Force equals the negative of the spring coefficient, k, times the length stretched, x. There is a negative because if you pull it to the right, it pushes to the left. Not all springs are linear and even your common springs are not exactly linear, but it is close enough. As you dig into science, you will find that many of the things you learn are not exact but pretty close. Maybe that is more true for engineering than science.