btrettel

92 ms·

901.
by btrettel 8y ago
I don't know much about high speed flows, but I imagine the answer is no. While the gas temperatures would be higher due to viscous heating, which would increase the viscosity of the air, the increase in viscosity is much lower than th
902.
by btrettel 8y ago
Glad to help. Here's some additional comments you or some other reader might find useful: Dimensional homogeneity is the most important constraint I think most machine learning folks would miss. It's not really an "inductive
903.
by btrettel 8y ago
Fluid dynamicist here. Short version: Scale models (like wind tunnels) are useful because the most accurate simulations are extremely computationally expensive or computationally intractable, and the faster less accurate simulations are oft
904.
by btrettel 8y ago
Thanks for the interesting example. You're right that this is unlikely to redeem a scaled up dandelion, but I thought it was still worth mentioning as it's often overlooked. I work in internal and multiphase flows, and changing th
905.
by btrettel 8y ago
You're most likely right, but there is at least one caveat which might be able to help if we're lucky. (I'm a fluid dynamicist, though not an aerodynamicist.) The Reynolds number is only part of the picture. You also need a m
906.
by btrettel 8y ago
Is there a better introduction to these ideas than Wikipedia? It makes intuitive sense, but I'd like to see the proof of this statement. Wikipedia mentions a "good regulator theorem", but the citation is pretty bad: "Con
907.
by btrettel 8y ago
Thanks, I was hoping someone would be able to point me towards a similar file manager!
908.
by btrettel 8y ago
I used to use an old Linux file manager called DFM back in 2002 to 2006 or so. Doesn't seem to be online any longer, but this looks like a copy of the original website sans graphics: http://distro.ibiblio.org/amigolinux
909.
by btrettel 8y ago
This is often more true than many believe. But in my experience few students get so far that they recognize the patterns and can respond in the way you describe. That might be the crux. I remember my undergraduate mechanical vibrations clas
910.
by btrettel 8y ago
Theoretical fluid dynamicist here. I solve a lot of not nice differential equations exactly or approximately. Whether numerical methods are viewed as the primary way forward is a bit of a self-fulfilling prophecy. If you don't think an
911.
by btrettel 8y ago
https://bicycleuniverse.info/bicycling-wastes-gas/ According to this a "typical" omnivore cyclist produces about 3 times less carbon than a "typical" driver. Vegan and vegetarian are about 4 times l
912.
by btrettel 8y ago
You're correct that much larger changes are needed. I don't claim my approach would solve the problem, just be one step towards a solution. I don't even know what a complete solution looks like, but I do know the changes I&#x
913.
by btrettel 8y ago
I was reading a blog post about problems in academia which said the following in the first paragraph: > There’s a narrative I find kind of troubling, but that unfortunately seems to be growing more common in science. The core idea is tha
914.
by btrettel 8y ago
It's both an infrastructure and driver behavior problem. As a daily transportation cyclist for about 10 years, I know from experience that much bike infrastructure in the US is more safety theater than actual safety improvements. Infra
915.
by btrettel 8y ago
Millennial here too and I agree. I want to add that "drop" is used only for music I don't listen to and that I never use the word drop to mean release in any context.
916.
by btrettel 8y ago
I don't think you are responding to what I wrote. I never suggested a one-size-fits-all approach. I don't think the 85th percentile rule is entirely bad, just not a "best practice", which sounds to me like "one-size
917.
by btrettel 8y ago
How common are the issues you mention? I hear a lot more complaints from drivers having to pay legitimate sounding speeding tickets than I do bogus tickets. In fact, I can't think of a single instance of anyone I know who got a speedin
918.
by btrettel 8y ago
I don't think following the rules of the road the vast majority of the time is that hard. Yes, you will make mistakes from time to time, but any reasonable system would recognize that. And sometimes following the law is less safe, but
919.
by btrettel 8y ago
Protected bike lanes in the US are far too often built in ways that increase risk. In Austin, I basically refuse to use the two most significant protected bike lanes near where I live and work because drivers far too frequently turn into th
920.
by btrettel 8y ago
Cycle commuting is probably at least a bit of a fad over the past decade, maybe a fading fad. I say this as a dedicated cycling commuter for about 10 years. So I think this might explain part of a decline, assuming it is statistically sign
921.
by btrettel 8y ago
Dimensional analysis, one of the topics in the book, is a favorite of mine. Unfortunately the more useful parts of the subject are not that well known. Fortunately, this book seems to have a fairly standard introduction to the subject. Most
922.
by btrettel 8y ago
That's a good strategy, but you should have other tools for non-linear problems in your toolbox too. I mostly want to push back against the idea that non-linear means unsolvable. My example transformed the problem to a linear one, but
923.
by btrettel 8y ago
I don't like that attitude. There are many non-linear problems which can easily be solved accurately numerically or exactly. So few people even try to solve problems exactly now that it seems like magic when someone does it. I can reca
924.
by btrettel 8y ago
"Model inadequacy", i.e., the model being wrong, is also a major source of error. In my training, it was basically assumed that floating point errors are negligible these days, so I'll check out your recommendation. If you&#x
925.
by btrettel 8y ago
If I were every to have input into the curriculum for an engineering program, I'd stress adding more about verification and validation of models, not adding more on numerical methods in general. All users of off-the-shelf models must d
926.
by btrettel 8y ago
Interesting paper. I work in fluid dynamics and tend to agree that computational power often is wasted. To elaborate on a point not discussed in the paper: Many methods used in practical engineering won't necessarily converge to the em
927.
by btrettel 8y ago
> The interesting thing is how people react to it. For some reason you are expected to provide a reason for why you don't drink. I don't smoke either but nobody asks me why. I've noticed also that it makes people uncomfort
928.
by btrettel 8y ago
> It's such an odd collective viewpoint that a vehicle which virtually always travels far below the speed limit should be allowed alongside vehicles that travel at the speed limit. Most cyclists are slower than the speed limit on mo
929.
by btrettel 8y ago
Reread my comment, as I don't know what you are referring to. I never said bikes are better in every way, or even more efficient. Actually, I think a well designed motor vehicle could easily beat a bike in efficiency, particularly for
930.
by btrettel 8y ago
> returning to the bicycle, an 18th century city technology, is regressive, not the way forward Just because something is old does not mean it is a bad idea. By the way, bicycles were first developed in the 19th century (not 18th) and ha

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