Need info, water flow rates.

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Got this one plot of an isekai'd MC stranded somewhere like a bayou, very wet land formerly a ruined sunken castle. He gets a bucket or some container to "drain the swamp" so he can uncover something crucial plotwise. Assume the water is automagically stored or sent elsewhere for a time, and environment issues are not a problem otherwise.

Question. Regarding typical human strength, what rate of water flow could a say 15ish yr old boy withstand holding.

Better question. Assuming an above water flow rate, how long could the same person stand in one place, to "drain the swamp"? Er wait, should I estimate a swamp in thousands, millions, or even billions of gallons or liters of liquid?

I also might assume for a swamp (unnaturally placed, by will of a deity 4 centuries back) the ground beneath the water might still be uneven and I might only need to drain a particular "bowl-shape" area to get at a particular thingamabobber.
 

Fighterman481

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Hey, doing some math so it's going to be a few minutes, but would you mind elaborating on the physique of the boy? Athletic, scrawny, etc? It'll help me get a better picture while I'm doing this :)
 

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Common build, not so muscular but he was an office worker before. A 30yo man de-aged to 15 for a reason, right before a competing deity throws him into said swamp area. Probably more toward scrawny than thin, but in a backyard fight he'd stand his ground. (Edit: probably more willing to talk a way out of a fight than get physical though he'd do what's necessary. He knows to drain the area first is his way to survival, so he's motivated to withstand all he can.)
 
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Parts of a swamp I plan may be wading/knee deep; the key area is probably chest deep at center, 50 m wide by 200 m long as an elongated watercourse. But other water may more or less run in after the fact too; it's a matter of time issue. Don't know what water flow would do on its own without leaving the result to "magic factors".
 
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... or have I thus far written myself into a proverbial corner.

I saw somewhere the water pressure on city fire hydrants and didn't know if that could be used as a baseline. Water would be flowing into the bucket from the way he holds it into the swamp water. I presume until he gets his bearings or makes drainage progress, he'd pretty much hold it straight forward.
 

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Alright this is turning out to be longer than expected I'll have a TL;DR at the bottom but I'd recommend reading everything if you want the best picture of what's going on or want to tweak things yourself.

So, flow rate is area of the pipe or channel times the velocity of the liquid. Velocity of your liquid is going to depend on the angle you place the bucket (I think), but let's say it's flowing at roughly the speed of a river. That goes from around 0 m/s to 3.1 m/s according to google, so that's what we've got to work with. We can always bring it higher by saying the bucket has a sort of suction function, so if it turns out that we can go higher we can always do that. Or just make the thing bigger like you mentioned.

So, we need to get the amount of force a 15ish year old boy could handle. If we listen to an answer from stackoverflow, the force of moving water on a wall would come out to F = pAv^2, where p is density (for simplicity's sake we'll assume 1. It's a swamp so it's likely higher than 1 but I'm not finding any average densities of swamp water soooo), A is area, and v is velocity. And, since we control area and velocity we can make our force basically whatever we want.

Unfortunately, there isn't much information on how much a child can lift and hold, and I'm not exactly sure how to calculate that. So, I'm going to be doing some synthesis and guesswork and I can't guarantee accuracy of this next bit. I'm going to be going off deadlift standards and then, since we're assuming holding it in place for a while, I'll be subtracting a decent amount off of that to assume the amount that kid can keep in place.

Deadlift standards are, apparently, based off of body weight. I'm going to be doing all my calculations in metric units because it just makes the math a lot simpler not having to convert back and forth, so keep that in mind. The average weight of a 15 year old boy is 56 kg, but since we're assuming he's towards the scrawnier side, I'll just call it an even 50, which is roughly the average for a 14 year old. A man weighing 50 kg has a standard deadlift of 44 kg if they're an absolute beginner (which I'm going to assume since he was an office worker).

Let's bring that down to 35 kg to assume holding in place. That's 343.35 Newtons. Let's assume velocity is at that maximum of 3.1 m/s we saw earlier, so if we divide our force by that our target area would be 35.72 m^2, or a circular object with a radius of 3.3 meters, and that's kind of a yikes if we're looking at a bucket or something. So, we'll go ahead and bump up that 3.1 m/s, say double it. This brings our target area all the way down to 8.9 m^2, or a circular object with a radius of 1.68 m. That's still huge for a bucket, but if we assume some sort of large box or something we could do a square container with a side length of 2.9 m.

Of course, I think it's easier to increase flow rate and assume magic shenanigans, so let's just make it a solid 10 m/s. That's super fast, and brings our theoretical bucket radius down to 1.09 m. If you want a bucket with a more reasonable (but still pretty large imo) radius that's a flow rate of 20 m/s and a radius of .52 m.

That gives us a flow rate of 16.989 L/s. Let's assume a small key area of 100m x 100m with an average height of ~85 cm (half of the height of an average 15 year old boy). Assuming the swamp is a perfect cube (which it's not), which is an area of 8,500 L. That'll take almost 500 seconds even to drain, so honestly not that bad.

So, TL;DR:
Considering average weights, a teen boy could maybe hold a force of 343.35 Newtons for a decent while and if you want to utilize all of that, you either need a big container or some sort of suction power on it. Considering a suction making the speed 20 m/s that's a bucket with radius .52 m (which is still decently big imo. Roughly a foot and a half). It'd take just under over 8 minutes to drain a fairly small (100mx100m) chest-high swamp.

If you have any questions, please ask, I can explain more or do some more tinkering for you!
 

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Yes. The magic suction was what I intended. Thank you.

So if I just round to maybe 7 to 8 minutes of holding in place ... this will likely get me in the range.
 
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