Life at Low Reynolds Number (1976) [pdf]
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Life at Low Reynolds Number (1976) [pdf]
1–10 of 11 posts
Re: Life at Low Reynolds Number (1976) [pdf]
#2Beautiful illustrations!
Re: Life at Low Reynolds Number (1976) [pdf]
#3So this sent me down the wikipedia rabbit hole :D
One thing I never realised is how dramatically the viscosity of water changes with temperature. This is probably why you can recognise hot water from a cold water in a video.
Temperature (C) / Viscosity (mPa*s)
0.01 1.7911
10 1.3059
20 1.0016
25 0.89002
30 0.79722
40 0.65273
50 0.54652
60 0.46603
70 0.40355
80 0.35405
90 0.31417
99.606 0.28275
Re: Life at Low Reynolds Number (1976) [pdf]
#4So this sent me down the wikipedia rabbit hole :D One thing I never realised is how dramatically the viscosity of water changes with temperature. This is probably why you can recognise hot water from a cold water in a video. Temperature (C) / Viscosity (mPa*s) 0.01 1.7911 10 1.3059 20 1.0016 25 0.89002 30 0.79722 40 0.65273 50 0.54652 60 0.46603 70 0.40355 80 0.35405 90 0.31417 99.606 0.28275
I had the pleasure to measure that in a university lab, it's very apparent when measuring near 0°C takes roughly 2x longer than on room temp.
Re: Life at Low Reynolds Number (1976) [pdf]
#5So this sent me down the wikipedia rabbit hole :D One thing I never realised is how dramatically the viscosity of water changes with temperature. This is probably why you can recognise hot water from a cold water in a video. Temperature (C) / Viscosity (mPa*s) 0.01 1.7911 10 1.3059 20 1.0016 25 0.89002 30 0.79722 40 0.65273 50 0.54652 60 0.46603 70 0.40355 80 0.35405 90 0.31417 99.606 0.28275
[deleted]
Re: Life at Low Reynolds Number (1976) [pdf]
#6The author of this paper is Ed Purcell - https://en.wikipedia.org/wiki/Edward_Mills_Purcell
If you studied physics in college, you may have used the textbook he wrote, Electricity & Magnetism.
Re: Life at Low Reynolds Number (1976) [pdf]
#7So this sent me down the wikipedia rabbit hole :D One thing I never realised is how dramatically the viscosity of water changes with temperature. This is probably why you can recognise hot water from a cold water in a video. Temperature (C) / Viscosity (mPa*s) 0.01 1.7911 10 1.3059 20 1.0016 25 0.89002 30 0.79722 40 0.65273 50 0.54652 60 0.46603 70 0.40355 80 0.35405 90 0.31417 99.606 0.28275
I've sometimes thought that the sound of water in my shower changes as the water reaches max temperature. Perhaps that's why?
Re: Life at Low Reynolds Number (1976) [pdf]
#8So this sent me down the wikipedia rabbit hole :D One thing I never realised is how dramatically the viscosity of water changes with temperature. This is probably why you can recognise hot water from a cold water in a video. Temperature (C) / Viscosity (mPa*s) 0.01 1.7911 10 1.3059 20 1.0016 25 0.89002 30 0.79722 40 0.65273 50 0.54652 60 0.46603 70 0.40355 80 0.35405 90 0.31417 99.606 0.28275
I wonder how pressure affects that, particularly near boiling.
Re: Life at Low Reynolds Number (1976) [pdf]
#9So this sent me down the wikipedia rabbit hole :D One thing I never realised is how dramatically the viscosity of water changes with temperature. This is probably why you can recognise hot water from a cold water in a video. Temperature (C) / Viscosity (mPa*s) 0.01 1.7911 10 1.3059 20 1.0016 25 0.89002 30 0.79722 40 0.65273 50 0.54652 60 0.46603 70 0.40355 80 0.35405 90 0.31417 99.606 0.28275
Another interesting temperature dependence of water is the negative thermal expansion between 0°C and +4°C. The maximum density is at +4°C.
Therefore, between 0 and 4°C the usual law of natural convection (heat rises) is inverted and you get "heat falls" instead.
What this means is that in winter, the ice on top of water can be frozen but the water can be warmer further down and resist further heat transfer. Natural convection will not act to cool the water from above, and a stable stratified temperature gradient can form. This allows bodies of water to remain liquid in winter for longer than you'd expect in a "normal" liquid.
Re: Life at Low Reynolds Number (1976) [pdf]
#10Hmm, it looks like (TFA author) Purcell's "Back of the Envelope" AmJPhys column, paywalled for decades by AAPT, is currently available online.[1]
"a monthly feature [...] from January 1983 through July 1984. Three new "order-of-magnitude" problems were presented each month [...] there were 57 problems, the discussion of which fills something like 150 column-inches". Eg, the ratio of tide influence from Moon and Sun is 7/3, so what is the ratio of their mean density?
[1] https://www.aapt.org/Publications/AJP/Readers/back_of_the_en...