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Trails of COVID... dispersion behind a walking person

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Trails of COVID... dispersion behind a walking person

 
Old 12-15-20, 01:00 PM
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genec
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Trails of COVID... dispersion behind a walking person

This isn't good news... Studies have shown that the COVID laden droplets can hang in the air and follow a person... thus your following distance should likely be further... depending on indoors, outdoors and speed of travel. (this means drafting can be especially bad.)



Computational simulations have been used to accurately predict airflow and droplet dispersal patterns in situations where COVID-19 might be spread. In the journal Physics of Fluids, by AIP Publishing, results show the importance of the shape of the space in modeling how virus-laden droplets move through the air.

The simulations are used to determine flow patterns behind a walking individual in spaces of different shape. The results reveal a higher transmission risk for children in some instances, such as behind quickly moving people in a long narrow hallway.
https://scitechdaily.com/safe-social...d-individuals/
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Old 12-15-20, 02:17 PM
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I got COVID dispersal training years ago. While boatbuilding and working with chemicals that wreaked havoc with reactions, allergy-like symptoms,sinuses, etc. I developed reactions to many common substances. Tobacco was one. I learned to hold my breath anytime it was there to be smelled. Both the direct smoke and the exhales. Even their clothing. Very useful now. I know very well where not to be,
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Old 12-15-20, 02:29 PM
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Originally Posted by 79pmooney View Post
I got COVID dispersal training years ago. While boatbuilding and working with chemicals that wreaked havoc with reactions, allergy-like symptoms,sinuses, etc. I developed reactions to many common substances. Tobacco was one. I learned to hold my breath anytime it was there to be smelled. Both the direct smoke and the exhales. Even their clothing. Very useful now. I know very well where not to be,
In stores, I often like to hold my breath briefly while passing a person (don't breath in their face either). Then exhale once passed followed by breathing again.

Of course, that means a couple of deep breaths too.

Keep in mind that one or two virus particles generally won't cause an infection. One may need a few hundred of them. Thus a long period of contact without protection.
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Old 12-15-20, 02:34 PM
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Originally Posted by CliffordK View Post
In stores, I often like to hold my breath briefly while passing a person (don't breath in their face either). Then exhale once passed followed by breathing again.

Of course, that means a couple of deep breaths too.

Keep in mind that one or two virus particles generally won't cause an infection. One may need a few hundred of them. Thus a long period of contact without protection.
This also explains why you canít escape the accusation of passing gas just by walking away.
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Old 12-15-20, 02:58 PM
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We do need to thank the vapers and smokers for helping us learn a bit about particle flow in different environments.
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Old 12-15-20, 03:10 PM
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Originally Posted by CliffordK View Post
In stores, I often like to hold my breath briefly while passing a person (don't breath in their face either). Then exhale once passed followed by breathing again.

Of course, that means a couple of deep breaths too.

Keep in mind that one or two virus particles generally won't cause an infection. One may need a few hundred of them. Thus a long period of contact without protection.
I do the same thing, except I don't need to take in a deep breath afterwards. My secret: anaerobic training. Having a good aerobic base is good, but your cardio/pulmonary system isn't at perfect efficiency without anaerobic training. I'm very conscious of my breathing when around other people.

Since this pandemic, I've become amazed at how in shape this 56-y/OLD dude is
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Old 12-15-20, 03:27 PM
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This of course all goes to show that even with "social distancing," masks are still important... you could be walking right into a cloud of COVID you had no idea existed. And of course, wash your hands.
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Old 12-15-20, 03:39 PM
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Originally Posted by work4bike View Post
I do the same thing, except I don't need to take in a deep breath afterwards. My secret: anaerobic training. Having a good aerobic base is good, but your cardio/pulmonary system isn't at perfect efficiency without anaerobic training. I'm very conscious of my breathing when around other people.

I can swim 50m underwater but I still need deep breaths to recover.
Same with cycling, I hold breath and move 10ft into lane if I need to pass someone on the sidewalk, but I still need some deep breaths to recover.
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Old 12-15-20, 03:42 PM
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Originally Posted by noisebeam View Post

I can swim 50m underwater but I still need deep breaths to recover.
Same with cycling, I hold breath and move 10ft into lane if I need to pass someone on the sidewalk, but I still need some deep breaths to recover.
That's not the same as walking by someone holding your breathback at ya
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Old 12-15-20, 06:18 PM
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I'm suspicious of any of these particle simulations. I still remember the one from the summer that opined cyclists should stay incredible distances away from other riders (60 feet and the like). It had just enough of a kernel for people to jump on it and believe it, but as far as predicting disease transmission, sorely lacking. And it refused to go away, even after it was debunked.

I'll say this too. I know quite a few people riding in small groups, and know of no one who has been infected with COVID from an encounter on a bike, and I know of no one who has even heard of anyone being infected in that manner. Perhaps it is part of the beast of contract tracing under those circumstances, but I remain skeptical. Has anyone heard ... even third or fourth hand ... of such a thing?
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Old 12-16-20, 06:38 AM
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Originally Posted by Biker395 View Post
I'm suspicious of any of these particle simulations. I still remember the one from the summer that opined cyclists should stay incredible distances away from other riders (60 feet and the like). It had just enough of a kernel for people to jump on it and believe it, but as far as predicting disease transmission, sorely lacking. And it refused to go away, even after it was debunked.

I'll say this too. I know quite a few people riding in small groups, and know of no one who has been infected with COVID from an encounter on a bike, and I know of no one who has even heard of anyone being infected in that manner. Perhaps it is part of the beast of contract tracing under those circumstances, but I remain skeptical. Has anyone heard ... even third or fourth hand ... of such a thing?
That borders right on the edge of the classic COVID denial of "do you know anyone with COVID..."

Frankly... though, 60 feet seems like a long distance to separate. Gee how far away should one be from a car with a COVD driver and/or passengers? Or a Sturgis attending motorcyclist?
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Old 12-16-20, 08:46 AM
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Originally Posted by Biker395 View Post
I'm suspicious of any of these particle simulations. I still remember the one from the summer that opined cyclists should stay incredible distances away from other riders (60 feet and the like). It had just enough of a kernel for people to jump on it and believe it, but as far as predicting disease transmission, sorely lacking. And it refused to go away, even after it was debunked.

I'll say this too. I know quite a few people riding in small groups, and know of no one who has been infected with COVID from an encounter on a bike, and I know of no one who has even heard of anyone being infected in that manner. Perhaps it is part of the beast of contract tracing under those circumstances, but I remain skeptical. Has anyone heard ... even third or fourth hand ... of such a thing?
If you travel at 20mph, which is a very common pace for enthusiast group rides, you cover 60' in 2 seconds. Based on the picture at the start of this thread, the virus is very much still clumped together at 2 seconds when outside. Perhaps this is why its been difficult for some to let go of the suggestion and instead ride even closer than 60'.
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Old 12-16-20, 09:25 AM
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Two things strike me when I read this article.

1) It is about droplet dispersal patterns and is about the physics, it says nothing about infectious dose - it leaves that to the imagination.

2) It is about walking in narrow corridors inside.

It needs to be coupled with some research about infectious dose and the likelihood of infection, otherwise people just take it and run with it and start speculating and you end up with a bunch of nonsense.
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Old 12-16-20, 09:36 AM
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I am as cautious as any regarding masks and distancing for the past nine months +, but this seems like a good example of the "spherical cows" phenomenon.
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Old 12-16-20, 10:54 AM
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Originally Posted by skookum View Post
Two things strike me when I read this article.

1) It is about droplet dispersal patterns and is about the physics, it says nothing about infectious dose - it leaves that to the imagination.

...
+! The science of fluid flow is well known. Computer modeling of objects and flow work. Now when I was studying fluid flow in the early '70s, computer power and the algorithms weren't there yet. We had to build solid model and test them in wind or water tunnels. Now, fluid flow is a series of random events. (Millions of very small interactions of fluid particles, each governed by strict physical laws and a random starting point. The computer program is similar but will never be exactly the same. The starting point is not random but that which is modeled in by those coding the program and model.

It should be noted that it is the right hand diagrams that matter, not the left hand diagram of a person in a corridor. On the right, you can see that if we are going upwind and drafting in the usual manner, our mouth and nose are in the upper portion of the cloud almost the whole time. (I can vouch for that. Draft someone who has been smoking pot and you get to do a quality assessment.)

Those COVID models look to be done well. But what isn't nearly as well known is how much exposure matters. And here is where things get really messy. The same number of viable virus particles will infect one person and not another. I"m guessing that if a person picks up X number of particles "here", say on a group bike ride, then simply goes back to his safe home and quarantines, he may be fine but if he then goes out shopping (masked) and sees that many particles again, that might be enough to infect him (or make him an asymptomatic carrier but that is another can of worms).

Being in a living situation where if I become one of those asymptomatic carriers someone else dies has kept this quite real for me.
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Old 12-16-20, 12:15 PM
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I'm not criticizing the physics, I am just pointing out they are referring to a person walking in a narrow corridor inside.
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Old 12-16-20, 12:21 PM
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Originally Posted by skookum View Post
I'm not criticizing the physics, I am just pointing out they are referring to a person walking in a narrow corridor inside.
The right hand diagrams are of open spaces.
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Old 12-16-20, 01:01 PM
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Our own planet is now needed . after the crisis is over we can return to earth.
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Old 12-16-20, 03:00 PM
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Originally Posted by rossiny View Post
Our own planet is now needed . after the crisis is over we can return to earth.
That won't work. We will just bring this COVID along with us. New scenery, same problem.
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Old 12-16-20, 03:22 PM
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Originally Posted by Biker395 View Post
I'm suspicious of any of these particle simulations. I still remember the one from the summer that opined cyclists should stay incredible distances away from other riders (60 feet and the like). It had just enough of a kernel for people to jump on it and believe it, but as far as predicting disease transmission, sorely lacking. And it refused to go away, even after it was debunked.

I'll say this too. I know quite a few people riding in small groups, and know of no one who has been infected with COVID from an encounter on a bike, and I know of no one who has even heard of anyone being infected in that manner. Perhaps it is part of the beast of contract tracing under those circumstances, but I remain skeptical. Has anyone heard ... even third or fourth hand ... of such a thing?
Originally Posted by skookum View Post
Two things strike me when I read this article.

1) It is about droplet dispersal patterns and is about the physics, it says nothing about infectious dose - it leaves that to the imagination.

2) It is about walking in narrow corridors inside.

It needs to be coupled with some research about infectious dose and the likelihood of infection, otherwise people just take it and run with it and start speculating and you end up with a bunch of nonsense.
You all can wait for proper studies (that may never come) that prove or disprove your beliefs. I'll continue to avoid being in anyones dispersal zone... and hold my breath during the moments I can't.
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Old 12-16-20, 06:09 PM
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Originally Posted by genec View Post

Frankly... though, 60 feet seems like a long distance to separate. Gee how far away should one be from a car with a COVD driver and/or passengers? Or a Sturgis attending motorcyclist?
If I actually knew a rider in front of me had an active infection, I'd sure want 60 feet. And I'd turn at the next crossroad.
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Old 12-17-20, 04:13 PM
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Originally Posted by skookum View Post
Two things strike me when I read this article.

1) It is about droplet dispersal patterns and is about the physics, it says nothing about infectious dose - it leaves that to the imagination.

2) It is about walking in narrow corridors inside.

It needs to be coupled with some research about infectious dose and the likelihood of infection, otherwise people just take it and run with it and start speculating and you end up with a bunch of nonsense.

Yep And that is exactly what was said about that earlier study. It was based on particle physics ... not on any experimental data regarding infectious does or anything else. Bad "science."
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Old 12-17-20, 04:20 PM
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Originally Posted by genec View Post
That borders right on the edge of the classic COVID denial of "do you know anyone with COVID..."

Frankly... though, 60 feet seems like a long distance to separate. Gee how far away should one be from a car with a COVD driver and/or passengers? Or a Sturgis attending motorcyclist?
Yea, and more to the point ... if it were THAT contagious, we would all have been infected by now. Clearly not the case.
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Old 12-17-20, 04:25 PM
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Originally Posted by Biker395 View Post
Yea, and more to the point ... if it were THAT contagious, we would all have been infected by now. Clearly not the case.
Not yet.

From what I understand (and this changes almost daily) it is a case of exposure over time... So yeah, you are basically correct that a bit of distance should be OK... as long as you are not following an infected person for a long period of time. (Define "long..." I can't)

It seems to be an issue of accumulation... so a bit here, a bit there, not too bad, unless that is repeated over and over again in a short time. Further, the virus casing seems to be quite weak... so washing is a good way to keep it in check.
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Old 12-18-20, 06:00 AM
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Originally Posted by genec View Post
This isn't good news... Studies have shown that the COVID laden droplets can hang in the air and follow a person... thus your following distance should likely be further... depending on indoors, outdoors and speed of travel. (this means drafting can be especially bad.)





https://scitechdaily.com/safe-social...d-individuals/

No offense, but I don't see how any of this applies to drafting. This is all modeled on an upright average height person at walking speed, not a seated rider traveling at bicycling speed. The assumptions of both the positions and the airflow therefore have no resemblance to riding. I'd say drafting is a bad idea because we don't know whether it's safe, but this has almost no implications for that.
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