How fluid dynamics saved the Space Shuttle (w/ Dianna Cowern/Physics Girl) 

Thanks! It's more a matter of uncertainty than small margins of error. Because the physics is not well-understood, engineers have to overdesign things like the heat shield so that they can be confident they'll handle whatever unexpected thing (like gap fillers sticking out) that happens. In this mission especially, they were very cautious given what had happened with Columbia on the previous flight.

Yep. I tried to word things carefully there. You're right that laminar flow isn't always the best for keeping drag low overall - but that's a topic for a different video!

Same here. I couldn't resist slipping that footage in. I did, unfortunately, have to leave out the clips of the astronauts being ridiculous.

I would love to see that footage as well! Can you upload it separately maybe? :-) Or post a link to it?

Here's one of my favorite bits: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-gE9tLr31mJI.htmlm58s

+fyfluiddynamics yea, not bad, haha! Thanks :)

Just found the channel, it's amazing!, great work!. Any video about weather/environment with FluidDynamics :D

Gas is a fluid

Gases and liquids are both fluids. :)

Gas only moves as a liquid above a certain pressure, below that pressure it moves molecularly

Hi Abraham, thanks! If you check out my resources page over at FYFD, I have some recommendations for those interested in learning more about fluids: fuckyeahfluiddynamics.tumblr.com/links

Looks great your resources web page! , i already have a formation in calculus and fluid dynamics, but i dont feel comfortable with my math skills and knowledge... i already knew some of the resources there, i happen to have read the Anderson's book for the finite wing theory... I think i will stick with open calculus and the Anderson's book of aerodynamics for reinforce and master the math and physics of the subject... Thanks you very much!

I have to remark something about the video... its amazing, but it seems that it says that planes works under laminar boundary layer, and even its true that laminar boundary layer in general produce less drag than turbulent, it detach easly under adverse pressure gradients, badly damaging the aircraft performance (laminar separation bubble), thats why some sail planes induce early laminar to turbulent transition... and even there are some special airfoils that try to have a laminar boundary layer for most of the cord, for the adverse pressure gradient section they enforce the turbulent boundary layer, and in general comertial planes works mostly under turbulent boundary layer.... I'm almost sure you know all of this and more.. but i had to say it ;) ... good luck, and again, your channel its amazing!

Yes, you're right that turbulent flow (on part of the wing) can be helpful. There's a reason I phrased things carefully by saying laminar boundary layers caused less friction-based drag. But getting into the details of vortex generators, stall conditions, etc. was not the point of this video and I wanted to avoid confusing matters for viewers unfamiliar with those topics. Also, they're good fodder for videos of their own!

Thanks for clarifying that. I apparently missed it when you said "friction-based drag" and so started composing a comment asking this exact question.

Great questions all around, Chad! It turns out that at high Mach numbers laminar boundary layers are remarkably resistant to going turbulent (a least due to roughness). What generally happens during re-entry (ignoring roughness effects) is that the boundary layer under something like the Space Shuttle stays laminar until a critical altitude where the speed of the vehicle and density of the air is such that turbulence occurs. Typically, this doesn't occur until lower in the atmosphere, when the Shuttle has already lost much of its speed. The concern is that large roughness could cause a turbulent boundary layer at higher altitudes and Mach numbers, where the heating effects would be much worse. As for how people model compressible turbulence, that's very much an area of active research. As with incompressible turbulence, there are many models available to choose from. For simple geometries (like a flat plate), it's possible to do Direct Numerical Simulation and solve the governing equations exactly all the way down to the Kolmogorov scale. Obviously, that's not realistic to do for the full Space Shuttle, so NASA often uses a combination of models and methods. For example, they can combine high and low fidelity simulations, wind tunnel testing, and flight data from previous Shuttle missions to estimate the impact of a given piece of roughness. In fact, that's some of the info that went into the Boundary Layer Transition Tool NASA engineers used to try and predict the impact of those gap fillers. In the end, they didn't have enough certainty in their predictions to outweigh the risk, so they recommended pulling those two gap fillers. You can read all about it in their report: ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20060022549.pdf

Great question! Personally, I'm a big proponent of the metric system -- it's much easier, imo. However, as far as I'm aware, NASA uses English units, not metric. I assume this is due to being part of the federal government and being required to use the U.S. official system of measurement.

Thank you.

You're spot-on about the dimples on a golf ball causing turbulence. Because that roughness is going to help keep the boundary layer turbulent on both sides, the golf ball would spin like the football. The beach ball only sees the reverse Magnus effect when one side is turbulent and one is laminar. As long as both are the same (either both laminar or both turbulent), a ball will see the classic Magnus effect.

fyfluiddynamics ohhh i get it now. so i understood that video wrong. haha thanks Nicole.

No worries! It's a confusing concept that can take some time to wrap your head around. :)

What about a table-tennis ball? I always thought it had a very strong normal magnus effect, but it's small and relatively smooth so I wouldn't be surprised if it had laminar flow. On the other hand, table-tennis balls spin extremely fast and so perhaps will still create turbulent boundary layers on both sides. (Maybe I'll have to calculate me some Reynolds-numbers ...)

I don't know for certain, but I suspect ping pong balls usually have laminar boundary layers. But as long as the ball has the same boundary layer state on both sides (i.e. both laminar or both turbulent) then it will behave according to the classic Magnus effect. It's only when things are asymmetric - laminar on one side, turbulent on the other - that balls get the reverse Magnus effect.

Hi Aaron, While planets have boundary layers, they're generally very close to the ground. Earth's is on the order of hundreds of meters tall, but the atmosphere itself is tens of kilometers. What you see in the cloud layers of Jupiter is instead one of the outermost layers. When it comes to estimating wind speeds of the visible planets in our solar system, it's more likely that scientists are using those outer layers for estimation. In the boundary layer, by definition, the wind speeds will be lower due to the influence of the planet surface through friction.

@@fyfluiddynamics So.....yes?

@@aaronwilson9763 Nope. Planets have boundary layers, but that's not what you're seeing on Jupiter and it's not what scientists use to approximate wind speeds.

In fluid dynamics, most of our computational simulations start from the Navier-Stokes equations (which are basically Newton's laws written for a fluid). Those can be tough to calculate quickly, even for supercomputers, which is why we have to make simplifications that we refer to as models for parts of them. In the case of this Space Shuttle mission, NASA had tools that combined high-fidelity numerical simulations, wind tunnel data, and flight data to help them estimate what the effects of the roughness would be. In the end, they just didn't have enough certainty to take the risk, so they recommended pulling those two gap fillers.

I think that might be because lots of faucets have aerators in them. en.wikipedia.org/wiki/Faucet_aerator

Oh, that's what that thing is called. Everything makes sense now.

Apologies. Filming in a big echoing room is tough on the audio. I'm still trying to tweak settings to figure out what works best without picking up too much environmental noise.

It's not audiobooks, but I sometimes do dramatic readings for the Improbable Research podcast: www.improbable.com/category/the-weekly-improbable-research-podcast/ Here's one I did recently on a "Stress Analysis of a Strapless Evening Gown": www.improbable.com/2016/05/04/stress-analysis-of-a-strapless-evening-dress-podcast-62/

This is going to be awesome. If you do read an audiobook, please share in your RU-vid channel so I know the title of a book I'll want to buy next. Thank you!

It's not their voice it's the mic or some mistake in post processing Either way Great video

+Sharif Sircar i think she fucked up the editing....becouse Dianas footage on her channel is perfectly fine

They aren't using the same camera ,I think* Moreover,none of them are using the built in mic,both are using a external one