swansont

pi * diameter does not get you an area. Wrong units. A = pi * r^2 = pi * d^2/4

Wind tunnels literally have fans like this, but irrelevant if you are getting the same airflow from multiple fans. The air speed will be the same if you are moving the same amount of air through the same area. But if the air is moving slowly, it will not get sucked out of the top quickly. Here's where analysis comes into it, where you can avoid making potentially contradictory statements like this. Continuity matters in situations like this. You can't be moving more air in than you are moving out. Moving the air slowly is not in keeping with your desire to move air away from people quickly. Wild-Ass-Guess i.e. a proposal with no basis in modeling or analysis I suppose I was thrown by your statement in the OP where you said "You want the air to circulate so fast that if someone sneezes the water droplets will remain inside the room only a few seconds before it is sucked out the ceiling vent. " I've been basing my responses on what you said. Is this the scenario, or not?

Energy efficiency would seem to be orthogonal to the discussion. Airbrush seems to be implying that a large area of small fans somehow inherently gives rise to a different flow rate than a large fan "All I can say is if you have many vent fans sucking air out the ceiling, rather than one big fan that creates a wind tunnel, you distribute the motion and increase the area of the air moving up and out the ceiling." Changing the are will matter, but in the above quote it's not at all obvious that the example is changing the area (from the term "big fan" and that wind tunnels generally have a fan as big as the tunnel) It's the speed of the air that matters. The speed of the air being greater near a nozzle is only true near the nozzle, and it's not a given that there is any nozzle in this problem. Mainly what I want is Airbrush to present some science or engineering to back up a claim, rather than a WAG. This being a science discussion site and all. The scenario is proposing that air is only around for a few seconds, which sounds like you are getting 10 or so room changes per minute, instead of per hour. To do this, the air has to move faster, regardless of how you do it. My point is having the air move 60x faster is not an imperceptible change, as was claimed.

Changing the question doesn’t make the answer correct.

You said yourself a wind tunnel has a big fan. Where is the constriction? I ask again: how is one big fan vs lots of small fans different? (same area)

How is one big fan vs lots of small fans different? If you can’t model the behavior, how can you predict what happens?

How about some math/modeling to back up this claim

Most commercial places have ventilation systems that do up to 10-20 air changes per hour. A restroom might do 30. That means the air hangs around for minutes https://www.engineeringtoolbox.com/air-change-rate-room-d_867.html https://en.wikipedia.org/wiki/Air_changes_per_hour Which means that you need a flow rate that is much higher if you want air to only hang around for seconds. That's not "unnoticeably faster"

Retro-fit assumes you have a compatible geometry. What if the ductwork is in the walls?

How realistic is it to expect everyone to re-install their entire HVAC system? At best this would apply to new construction, in places where people don’t mind hanging out in a wind tunnel.

Claimed without support. Faster moving air means the virus can travel further before leaving the room, per the paper I linked to. Meaning you might infect everyone before getting a chance to filter the air. Hot air rises, so exiting through the floor isn't always the best option.

Not the problem described in the paper, which derives from in-room circulation. The air flow from the ventilation system assisted in getting the droplets to travel from table to table, before they would have had a chance to be filtered. We had a high-level person who insisted on stepping over the mats whenever he entered our lab. Grrr. (A tad like Pence not wearing a mask at the Mayo clinic) Anyway, I took to calling it admiral-paper. (And our visitors were referred to as sneetches, from the Dr. Seuss story)

I think even Iowa has cities.

Found this https://wwwnc.cdc.gov/eid/article/26/7/20-0764_article#tnF1 Strong airflow is alleged to be the culprit, since droplets travel further. Filtration doesn’t fix that. Some basis for the discussion, other than conjecture, is needed.

Not my burden of proof. But the scenario offered - nursing homes - has caretakers in close contact with multiple people on a daily basis. Has that been eliminated from being the prime suspect?

Clearly? What evidence is there to support this? What information do you have on air filtration removal of the virus? Can you reconcile your need for a high flow rate with this filtration/exposure plan?

Outside of my area of expertise, but unless the tissue is coated with whatever you’re trying to kill, I’d guess “no”

Inside the lungs even surface-level effects will be damaging. Radiation that only penetrates the top level of cells has been tested (this came up here or in a related thread) - it's in the deep UV. In one sense it's like alpha radiation. Externally not a problem because it's attenuated by the top layer of cells, but very damaging if ingested/inhaled. You would, in effect, be getting a sunburn inside your lungs.

What have the countries which have had the most success done?

Yeah, about Sweden... "Sweden: 22 Scientists Say Coronavirus Strategy Has Failed As Deaths Top 1,000" https://www.forbes.com/sites/davidnikel/2020/04/14/sweden-22-scientists-say-coronavirus-strategy-has-failed-as-deaths-top-1000/#1f42483e7b6c

It's kinda like the Stockholm syndrome in that regard. I didn't recall the name, either. I was double-checking which bias it was (wasn't sure if it fell under confirmation bias) and it popped up.

Then it's not a good example for the situation of a place that hasn't been able to get ahead of the spread of the virus (not that Sweden is doing great), and one should note that they are saying they are still a month away from herd immunity - in the capital. We don't know if/how well their strategy is going to work. As a counterexample, one can look at Singapore. Or look at the 1918-19 flu pandemic. The "second wave" was worse than the initial wave.

It's called the Baader-Meinhof phenomenon (frequency bias). Coupled with confirmation bias.

Try it in your country, and have someone report back.

How can a single entity be in equilibrium? That's like asking "what's the difference between a duck?"