Wind Tunnel Corrections and Data Reduction

Рет қаралды 9,149

Күн бұрын

This is the second of our 3 part series on wind tunnel testing. In this video, we discuss 11 different corrections and data reduction processes that are applied to raw wind tunnel data to transform it into data that more closely resembles full scale, free air flight.
Topics and timestamps:
0:00 - Introduction
4:20 - A. Indicated to actual q
22:32 - B. Balance interactions
56:58 - C. Tares: strut/fork, tare and interference
1:10:22 - D: Weight tares
1:20:25 - E: Moment transfers
1:27:31 - F. Blockage corrections
1:42:15 - G. Initial coefficients
1:45:41 - H. Flow angularity (upflow/crossflow)
2:09:01 - I. Wall corrections
2:36:58 - J. Final coefficients and corrected AoA
2:40:41 - Axis transfers
2:48:30 - References and conclusions
Lecture notes and code can be downloaded from github.com/clum/KZfaq/tree/...
All Wind Tunnel videos in a single playlist ( • Wind Tunnel Testing )
All Flight Mechanics videos in a single playlist ( • Flight Mechanics )
#FlightMechanics #WindTunnelTesting #UW
You can support this channel via Patreon at / christopherwlum or by clicking on the ‘Thanks’ button underneath the video. Thank you for your help!

Пікірлер: 72

@ChristopherLum 3 жыл бұрын

In case it is helpful, here are all the Wind Tunnel videos in a single playlist kzfaq.info/sun/PLxdnSsBqCrrEbjML0UneRVLn8YDoxql-i. All my Flight Mechanics videos in a single playlist are located at kzfaq.info/sun/PLxdnSsBqCrrEx3A6W94sQGClk6Q4YCg-h. Please let me know what you think in the comments. Thanks for watching!

@hrishikeshsivanandan9904 3 жыл бұрын

This is so much better than the lectures at TU Delft!!!

@ChristopherLum 3 жыл бұрын

@@hrishikeshsivanandan9904 I'm glad it was helpful, thanks for watching!

@zaneyosif 3 ай бұрын

AE512: Quite incredible how much steps there are to process wind tunnel data and spit out our beloved coefficients!

@WalkingDeaDJ 2 ай бұрын

Jason-AE512: An informative video that delves into the necessary adjustments needed to translate wind tunnel data to real-world applications. It systematically covers various corrections like blockage, flow angularity, and pressure adjustments, making complex concepts accessible.

@charlesharmon9065 2 жыл бұрын

Breaking the topic up into discrete sections made the time go by very quickly. Great lecture, and so interesting to compare and contrast with automotive aerodynamic testing that I've been involved with in the past. No flying cars just yet...

@philipcasey8361 3 ай бұрын

AE512: Thanks for the breakdown of each correction!

@boeing797screamliner 3 жыл бұрын

AA516 - great comprehensive lecture. During my undergrad wind tunnel experiments, most of these corrections were probably done for us so all we had to do was hit "run." Really interesting to see what's going on behind the scenes

@user-hw8di2xk7f 5 ай бұрын

AA516: Celeste Yuan. We are planning to go into the wind tunnel and rewatching this really helped me understand how we plan to post-process the data!

@bsgove Ай бұрын

AE512: There are clearly so many opportunities for error here when performing tests, acquiring data, and interpreting said data. It's amazing that significant meaning can be derived from the tests.

@Kumky605 5 ай бұрын

AA516: Forgot to comment on this when I watched it the first time but wish we had this explained to us this well in junior lab!

@nathanlipshutz3140 3 ай бұрын

AE512: I did not realize all the nuance involved in wind tunnel data reduction! Lots of correction factors and reference frames.

@petermay6090 5 ай бұрын

AA516: very thorough, thank you for the in depth explanation and resources!

@EomjiKim 5 ай бұрын

AA516: Thank you for clear explanation of each sections. Really helpful to understand on each elements applied for the wind tunnel test.

@sethwhittington28 2 жыл бұрын

AE512: Great intro to wind tunnel corrections. It makes sense that data collected from a wind tunnel has innacuracies from that of a real aircraft, but I hadn't thought about it before.

@liupeterw 5 ай бұрын

AA516 - I think this lecture was super interesting, as at first glance I wouldn't know what constraints and corrections to apply, but one by one could see how the model itself was eliminating uncertainties.

@rowellcastro2683 5 ай бұрын

AA516: Okay this was a lot of information to take in but it was a very interesting topic nonetheless. I remember when the KWT staff were explaining some of these corrections such as the inverted image and image fair in correction C. I kinda got the gist of it from their explanation but your explanation on all the corrections was more in depth and I feel that I learned a lot more as well as learned new things about data corrections, and specifically for the Kirsten Wind Tunnel. Thank you for this informative lecture proffesor!

@Colin_Baxter_UW 5 ай бұрын

AA516: Nice explanation of blockage ratio. Would be curious to see how close the results of the two methods would be.

@masontelander3847 2 жыл бұрын

AE512 Great video and really cool stuff. I wouldn't have thought it'd be as simple as a linear relation of the different testing orientations to work out strut and interference effects.

@ChristopherLum 2 жыл бұрын

Just note that this is how it is done at this particular facility. Personally, if the data really mattered for my application I'm not sure I would rely on a simple linear superposition argument, especially with such a complicated system like a wind tunnel test.

@tonymcdaniel6878 5 ай бұрын

AA516: Very cool that once I code these operations in matlab they are actually much simpler

@hasanhorata8381 2 жыл бұрын

AA 516 - A dense one, but a worthwhile one to watch. All this time I just thought you hit run on the wind and let the sensors do all the work

@chayweaver.2995 Ай бұрын

[AE512]: makes sense that there are so many corrections that have to be made in order to... well... correct for more realistic conditions the aircraft would be experiencing

@sunnysarkar7643 2 ай бұрын

AE 512: This video was great, but I was a little confused on how moments work as it has been years since I have last calculated a moment. Linking a video to that would be super helpful.

@ChristopherLum 2 ай бұрын

Which part of the moment calculation is confusing? Please remind me at office hours and I'd be happy to chat more about these.

@aimeepak717 3 ай бұрын

AE512: So many steps are needed to post process wind tunnel data!

@ChristopherLum 3 ай бұрын

I hope this gives us GNC engineers an appreciation of what the aerodynamics and S&C folks have to deal with before they hand us data to use in our models.

@ras22king 2 жыл бұрын

First of all, thank you for the beautiful lectures regards wind tunnel. I know it is difficult to match both Reynolds and Mach numbers in low speed wind tunnels therefore they use Reynolds number of 500000 to 750000 then extrapolate the results to the flight Reynolds number. Could you talk more about extrapolation techniques ?

@DB-zk3oq 3 жыл бұрын

This is really helpful thank you for sharing but How did drive the equations “delta_alpha_w” for the wall correction any ideas or if you could share sources about that please thanks 🙏

@leoschuhmacher1219 2 жыл бұрын

Your videos are extremely good and very visual explanations.This helps immensely, but one video I miss, there should be before the wind tunnel testvideos not perhaps one to the theoretical design of an aircraft in a program and the determination of all coefficients?

@ChristopherLum 2 жыл бұрын

Hi Leo, Thanks for reaching out. If you have questions or would like to request a video, I hope you'll consider supporting the channel via Patreon at www.patreon.com/christopherwlum. I'd love to have you as a Patron as I'm able to talk/interact personally with Patrons. Thanks for watching! -Chris

@_SpacemanSpiff 5 ай бұрын

AA516 - During weight tare, if I am just changing the yaw angle (keeping pitch angle at zero), will my rolling moment due to model weight change at BMC? From my understanding of geometry, it shouldn't change, if for imparting this yaw angle we are moving the complete support structure along with balance and the model. In this case the relative orientation between the balance and model does not change.

@vijayrathi7485 3 жыл бұрын

At 1:52:56 you mentioned about video - "angle of attack and angle of slideslip and relationship to body, stability and wind axes", but I am unable to find this mentioned video on your channel. Can you please provide the link of this mentioned video?

@_SpacemanSpiff 5 ай бұрын

AA516 - Why is it desired to have Ps2 close to 1atm? What are some other simulation parameters considered for a typical force measurement tests? Is it possible to maintain them when we fix our static pressure in test section at 1atm?

@rowellcastro2683 5 ай бұрын

AA516: 2:45:15 (AXIS TRANSFER: coeficient to Force). I would like to discuss more of this in office hours.

@ChristopherLum 5 ай бұрын

Yes, let's chat about this, please remind me.

@tilio9380 3 жыл бұрын

AA516 At the end when you rotated from stability axis to body axis, did you rotate it by the corrected AOA?

@ChristopherLum 3 жыл бұрын

Correct, you want to rotate by corrected alpha.

@christophervandenheuvel7563 3 жыл бұрын

(AA 516) I'm just wondering, for the final stage where the data is rotated to the stability frame: to avoid the confusion with the coefficient denormalization and renormalization, would it not be simpler to just record the forces and moments directly and then rotate those vectors? It seems like the same amount of data would be recorded, since the q measurements are needed anyway to transform the coefficients.

@ChristopherLum 3 жыл бұрын

Chris, you are correct, it is easier to deal with the force and moment vectors rather than the dimensionless coefficients. However 99% of the time you'll receive coefficient data that you'll need to manipulate so being comfortable with manipulating them is good practice.

@JushuaAbraham-sj2xl 6 ай бұрын

What about Reynolds number, shouldn't be the same for the model and the real aircraft especially in the subsonic regime?

@ojasvikamboj6083 Жыл бұрын

A A 516: Ojasvi Kamboj

@mohsenfazareh3384 Жыл бұрын

Hello every body Thanks for this video Does any body knows about the term "Center of reduction" what is it? where is it useful ?

@sakhralnakhlany5158 3 жыл бұрын

Cannot find the video you mentioned at 1:52:59 ..

@davidtelgen8114 3 ай бұрын

AE512: Do you think CFD will eventually be relied upon to replace some of the special wind tunnel testing configurations (no horizontal stabilizer run, etc), or will it always be cheaper/better to keep doing everything real world?

@ChristopherLum 3 ай бұрын

Currently it seems that CFD can be used in some circumstances and scenarios but a lot of people want to see real experimental data, especially for certification and validation

@timothylloyd1832 3 жыл бұрын

AA516: For the weight tare section, I can see how the three point tare method would yield us several equations and unknowns. I'm having trouble figuring out what those equations would be though. I'm trying to relate pitching and rolling moment to alpha, psi, and the distance from the BMC to the CG, but I can't figure out how I would back out the components of the vector (x,y, and z).

@ChristopherLum 3 жыл бұрын

Tim, I'm going to have the TA send you an excerpt from the solutions, hopefully that helps clarify some things. Let me know if you still have questions after that, thanks.

@jaziebart 3 жыл бұрын

Christopher Lum can you please send that to me as well if you get this in time? I have the same questions as Tim. Thanks!

@ChristopherLum 3 жыл бұрын

@@jaziebart Yes, I'll ask the TA to send it to you also.

@akarshshetty9262 Жыл бұрын

I'm confused as to why we can't move the Balance Moment Center to be positioned such that it coincides with the Center of Gravity of the Model, since C.G is something that is determined by the weight distributed in the model, but we do have the luxury of moving the Balance Moment center, right?

@ChristopherLum Жыл бұрын

Hi Akarsh, Thanks for reaching out, I'm glad you enjoyed the video. Unfortunately I'm unable to respond to questions on KZfaq due to the sheer volume of inquiries that I receive. That being said, I hope you'll consider supporting the channel via Patreon at www.patreon.com/christopherwlum or via the 'Thanks' button underneath the video as I'll be able to answer questions there. Given your interest in the topic, I'd love to have you as a Patron as I'm able to talk/interact personally with Patrons. Thanks for watching! -Chris

@binyulong5995 Жыл бұрын

AA516 How do aircraft engineers correct the difference between the coefficients of the model and the real airplane due to the Reynolds number difference? The smaller model has a flow field that is affected a lot more by viscous forces than the real one, and I imagine the difference is going to be even greater for turbulent flight conditions.

@ChristopherLum Жыл бұрын

Good point, there are many effects that are difficult to match between wind tunnel and free flight conditions. Mach, Re, and other effects need to be taken into account if you want to completely match conditions. Some tunnels are pressurized (ie the F1 ONERA tunnel) to try and better match these effects.

@zachsmith1973 Жыл бұрын

AA 516: Weight Tares -- curious how you actually go about finding cg location. I'm just using the definition of a moment and some trig, but still struggling to have things work out. Any tips?

@ChristopherLum Жыл бұрын

Yes, the trig can get a little nasty. I'd recommend using rotation matrices and a symbolic solver/manipulator like Mathematica.

@nathanlipshutz3140 3 ай бұрын

AE512: Why does lift not have angularity correction like Drag?

@ChristopherLum 3 ай бұрын

You can add this correction of you want but it is much smaller in proportion than the drag correction so often it is ignored