Fire Hose against a wall

[Rexone]

Since we're all into physics and thinky shit here's one for ya.
A fireman is standing 10 feet from a wall with a large firehose spraying water at full force. In fact it takes 2 fireman to hold the hose in place because of the horizontal force.
If you slide the wall away will the force against the firemen lessen?
:D :D

[bocco]

No.

[djunkie]

Just pay the man his phucking money already....... Ooops. Wrong thread. :jawdrop: :D :D

[HalletDave]

Since we're all into physics and thinky shit here's one for ya.
A fireman is standing 10 feet from a wall with a large firehose spraying water at full force. In fact it takes 2 fireman to hold the hose in place because of the horizontal force.
If you slide the wall away will the force against the firemen lessen?
:D :D
I don't think so.
:idea:
Maybe if somebody reduces the water pressure at the hydrant.;)

[Havasu1986]

Only if you turn down the water pressure. ;)

[ColeTR2]

No it will stay the same

[gramps]

Is the wall on a treadmill?

[clownpuncher]

ooh, ooh I know, I know.:D :D

[clownpuncher]

I don't think so.
:idea:
Maybe if somebody reduces the water pressure at the hydrant.;)
There we go again, bringing shit in to confuse everyone. BTW, we rarely, damn near NEVER fight fire with a hose fed from the hydrant;)

[Rock-A-Bye-Baby]

Does the wall take flight? Or does it slide away in reverse, thus inducing thrust, drag, and lift?

[Havasu1986]

There we go again, bringing shit in to confuse everyone. BTW, we rarely, damn near NEVER fight fire with a hose fed from the hydrant;)
Semantics. The fire hydrant has a 4" hose to the fire truck which has a smaller hose to the fireman.
:D

[Sotally Tober]

Nope!

[clownpuncher]

Semantics. The fire hydrant has a 4" hose to the fire truck which has a smaller hose to the fireman.
:D
Good word, I had to look that one :D up

[ratso]

Yes... I just tried it with a garden hose.

[Rexone]

I was hoping Tom Brown would offer his insight on this since it's widely known he's a hoser from way back.

[MADDOG355]

The force on the men remains the same.

[LAFD]

nope it will stay the same.

[photo chick]

The answer is yes!!
I'm just curious how many men it takes to slide a wall that's strong enough to withhold that much pressure!! :idea: :)

[RIPPINGNOLEGSKROKER]

In boating terms, a jetboat is no faster if it is roosting air or a wall.

[Strippoker]

no change that is 101 class

[R.A.D.man]

Just pay the man his phucking money already....... Ooops. Wrong thread. :jawdrop: :D :D
Fukkin Junkie. LOL.

[Cs19]

If you slide the wall away will the force against the firemen lessen?
:D :D
no, its all in the thrust created from water exiting the nozzle,what happens after that means nothing... same as a jetboat.

[riverroyal]

thats my final answer.When I used to race jetskies we had a race where we lined up against a seawall,It took less "throttle" for 2 guys to hold me,thus more force

[Riverkid]

thats my final answer,It took less "throttle" for 2 guys to hold me,thus more force
from your thread! :D

[MAINEVENT]

I don't think so.
:idea:
Maybe if somebody reduces the water pressure at the hydrant.;)
FYI... you can't Reduce the "Pressure" of water... Just the Flow/Volume...
And No it would not lessen...
K Folks Carry on... :eek:

[OverKill]

[SIZE="4"]I should know this (NO)
http://www.***boat.com/image_center/data/500/medium/0112.JPG

[fat rat]

This seems to be enjoying the thrust.
http://youtube.com/watch?v=eTslAcqDZu4

[boatsntoys]

Nope

[little rowe boat]

No, the wall has nothing to do with the pressure exerted at the nozzle, which is the nozzle pressure.The fire engine/ pumper is where the pressure on the nozzle is regulated. This is called engine pressure which takes into effect the length of the hose lay and the diameter of the hose both of which play a roll in determining the friction loss in the hose line, any gain or loss of elevation and finally the nozzle pressure itself.
Ex. a 200' hose lay through 2.5" hose pumping 200 gpm with a 100 psi nozzle pressure on level ground, figuring 10 psi of friction loss per 100' of hose will give you any eng. pressure of 120 psi.

[phebus]

A better question is, "Would it knock them out of their recliners"? :)

[3:30dirty]

No, the wall has nothing to do with the pressure exerted at the nozzle, which is the nozzle pressure.The fire engine/ pumper is where the pressure on the nozzle is regulated. This is called engine pressure which takes into effect the length of the hose lay and the diameter of the hose both of which play a roll in determining the friction loss in the hose line, any gain or loss of elevation and finally the nozzle pressure itself.
Ex. a 200' hose lay through 2.5" hose pumping 200 gpm with a 100 psi nozzle pressure on level ground, figuring 10 psi of friction loss per 100' of hose will give you any eng. pressure of 120 psi.
Must be an Engineer...:D Dont forget the friction loss of your appliance.:)

[little rowe boat]

Must be an Engineer...:D Dont forget the friction loss of your appliance.:)
:)

[Some Kind Of Monster]

The answer is no,
However, does the force increase if the hose becomes say, inches from the wall? For example it would be impossible for the firemen to make that hose nozzle touch the wall.
Good job of ruling that out of the question though. You deserve a sucker. :idea:

[ck7684]

The pressure against the wall or the firemen?

[OCMerrill]

Quite a few folks here on HB drive fire nozzles. As far as I can tell the only way to make them go is to squirt more water out the nozzle.
And with a diverter they can shoot about 90% if it in the air and still go forward at about the same rate.
So...my answer is....really a question;
Is the wall brick, common block, or slump stone? :D

[pw_Tony]

Damn it I read this yesterday, then last night in my dream I was trying to see what happen if I did it.... so in my Dream in made an affect, but does it? :D

[Froggystyle]

Yes, it does... but it has as much to do with the air pressure inside the cone of the hose as it does hydraulic pressure.
I am not sure of the exact physics of it, but a fire hose, focused to be approximately the same size as the outer edge of a doorway (6-8' diameter cone) from about 10' away moves more air through the doorway than you could possibly imagine. TONS more air than a blower or fan.
The hydraulic pressure of the water moving in a column is real too... if you had a straight stream, it would certainly decrease resistance at the hose.
You guys ever see the picture of the 8 hoses that lifted the car? Once it got a certain height up, it could climb no more, regardless of pressure.
In aviation it is called a ground effect I believe. You generate more lift close to the ground then you do further away from it.
I believe (not sure about this one...) that it takes more power to hover a helo at 200' then it does on the deck. Any aviators care to chime in on that one? From my understanding of it, the higher pressure air column underneath the helo increases lift essentially.

[Some Kind Of Monster]

In aviation it is called a ground effect I believe. You generate more lift close to the ground then you do further away from it.
I believe (not sure about this one...) that it takes more power to hover a helo at 200' then it does on the deck.
This is true. Very interesting. I have a battery powered heli that will only hover up to a foot off the ground when the battery gets low. :idea: I would argue that at 10 feet the wall makes little or no difference, but get closer??

[79Challenger]

So would the Space Shuttle be able to gain lift off if it were not on a launch pad?

[snake321]

I peed on the wall of my garage to test this theory and I only recieved 10% splashback on my shoes.
Can we move on now??

[Sleek-Jet]

In aviation it is called a ground effect I believe. You generate more lift close to the ground then you do further away from it.
I believe (not sure about this one...) that it takes more power to hover a helo at 200' then it does on the deck. Any aviators care to chime in on that one? From my understanding of it, the higher pressure air column underneath the helo increases lift essentially.
After doing a little more digging (and re-reading a favorite research paper), I'm going to retract the first few sentences... and send people here... http://www.allstar.fiu.edu/aerojava/airflylvl3.htm... I'm sure froggy has read it, pay attention to the ground effect paragraph at the end... now, back to our water hose... :D
Ground effect is usually noticed from a height of half the wingspan of the airplane. Airplanes will fly in ground effect that aren't able to climb out of it, some are even designed that way, and called ground effect aircraft. In Helos it's more of a cone shapped column of air at the top, but the same rule applies. It takes less energy (HP) to generate lift close to the ground.
All of this goes back to the Bernoulli/Newton argument on flight.
But, we are talking water and not air... Water does not compress... so it doesn't matter if the hose is 10 feet from the wall or spraying down the driveway, the force felt by the firefighters would be the same.

[spectras only]

In aviation it is called a ground effect I believe. You generate more lift close to the ground then you do further away from it.
When the Heli is on the ground the downwash from the rotor blades are deflected upwards and out , hence more lift generated close to the ground .
There is a lot of turbulence for the helicopter close to the ground , hence you can hover more stable higher up where you don't have this ground effect .

[ck7684]

If you move the wall far enough away, the water wont even be touching it, and there would be no pressure on it at all...

[little rowe boat]

But, we are talking water and not air... Water does not compress... so it doesn't matter if the hose is 10 feet from the wall or spraying down the driveway, the force felt by the firefighters would be the same.
Exactly.

[Froggystyle]

At some point I imagine I will be sick of cracking up at "experts" who just flat throw down the glove at what can and cannot happen... period.
But it isn't today... :D
The water, which is "uncompressable" as you describe it is moving in a column, and it has frictional characteristics against itself. A lot of it in fact. It is acting as a semi-solid column.
As an example, imagine if a steel rod was coming out of it, it would push the operator away.
The same thing is happenning, but with far less adhesion in the water column. The further away the wall gets, the less and less the attractive force the water retains to itself and the less likely the met resistance at the wall is to impact the operator.
You need to ask yourself this... does it work at 1'? Does it work at 1"?
If yes... then it works at 10', but to a lesser degree. It decreases rapidly after that as well...
You absolutely feel the difference. I have held a fire hose and hit a wall in front of me that I was firing over. HUGE difference in resistance.

[Froggystyle]

Exactly.
Your post here reminds me of Cal Naughton Junior from "Talledega Nights" when the kid says "My teacher asked me what the capitol of North Carolina was and I said Washington D.C." and Cal said "Bingo!"
:D

[spectras only]

I peed on the wall of my garage to test this theory and I only recieved 10% splashback on my shoes.
Can we move on now??
Next time you better stand far away to avoid that 10% splashback :)

[Sleek-Jet]

At some point I imagine I will be sick of cracking up at "experts" who just flat throw down the glove at what can and cannot happen... period.
But it isn't today... :D
The water, which is "uncompressable" as you describe it is moving in a column, and it has frictional characteristics against itself. A lot of it in fact. It is acting as a semi-solid column.
As an example, imagine if a steel rod was coming out of it, it would push the operator away.
The same thing is happenning, but with far less adhesion in the water column. The further away the wall gets, the less and less the attractive force the water retains to itself and the less likely the met resistance at the wall is to impact the operator.
You need to ask yourself this... does it work at 1'? Does it work at 1"?
If yes... then it works at 10', but to a lesser degree. It decreases rapidly after that as well...
You absolutely feel the difference. I have held a fire hose and hit a wall in front of me that I was firing over. HUGE difference in resistance.
OK... so at what point does the wall not have any effect??
It will change if you get really close the wall... after all that's how a hydraulic cylinder works, and incompressible fluid acting on an fixed surface.
But without knowing specifics of the column of water, you can argue both sides.

[little rowe boat]

At some point I imagine I will be sick of cracking up at "experts" who just flat throw down the glove at what can and cannot happen... period.
But it isn't today... :D
The water, which is "uncompressable" as you describe it is moving in a column, and it has frictional characteristics against itself. A lot of it in fact. It is acting as a semi-solid column.
As an example, imagine if a steel rod was coming out of it, it would push the operator away.
The same thing is happenning, but with far less adhesion in the water column. The further away the wall gets, the less and less the attractive force the water retains to itself and the less likely the met resistance at the wall is to impact the operator.
You need to ask yourself this... does it work at 1'? Does it work at 1"?
If yes... then it works at 10', but to a lesser degree. It decreases rapidly after that as well...
You absolutely feel the difference. I have held a fire hose and hit a wall in front of me that I was firing over. HUGE difference in resistance.
I have held many fire hoses on the drill grounds and on actual fires and there is no difference in the resistance or nozzle pressure that you feel, while holding the line.. It does not make a difference if you are firing down a drive way or at a wall. The nozzle pressure stays the same. The velocity of the water lessens the further away from the nozzle it travels. The water does have more velocity at the end of the nozzle and it decreases as it meets the forces working against it after it leaves the nozzle, gravity, wind, the friction of the air.( this is usually called point of breakover)
I have held a 2.5" hose line flowing 200 gpm at 100 psi nozzle pressure, pointing it straight up overhead, side to side and straight down at the ground.( When I came on the job this was part of our 1st 6 months probationary requirement) The nozzle pressure remains the same. No difference.

[Froggystyle]

I have held many fire hoses on the drill grounds and on actual fires and there is no difference in the resistance or nozzle pressure that you feel, while holding the line.. It does not make a difference if you are firing down a drive way or at a wall. The nozzle pressure stays the same. The velocity of the water lessens the further away from the nozzle it travels. The water does have more velocity at the end of the nozzle and it decreases as it meets the forces working against it after it leaves the nozzle, gravity, wind, the friction of the air.( this is usually called point of breakover)
I have held a 2.5" hose line flowing 200 gpm at 100 psi nozzle pressure, pointing it straight up overhead, side to side and straight down at the ground.( When I came on the job this was part of our 1st 6 months probationary requirement) The nozzle pressure remains the same. No difference.
Go try pointing that 2.5 at nothing, and side-step in front of a wall. Lean into it though... It will be dramatic.
The same thing happens exactly the same way with a garden hose. To test, run the hose at full blast and hold it back far enough on the hose to where the pressure coming out of it is supporting it up, but not far enough back where it is flopping around. Then put a piece of wood in front of it about 1-2'. The hose starts flopping all around wildly after taking a huge lurch backwards.

[boatsntoys]

Go try pointing that 2.5 at nothing, and side-step in front of a wall. Lean into it though... It will be dramatic.
The same thing happens exactly the same way with a garden hose. To test, run the hose at full blast and hold it back far enough on the hose to where the pressure coming out of it is supporting it up, but not far enough back where it is flopping around. Then put a piece of wood in front of it about 1-2'. The hose starts flopping all around wildly after taking a huge lurch backwards.
instead of spending hours on debate. Just went outside and tried it. Hose was laying clamly in the grass, high pressure was on, put a piece of plywood in front, and now I'm soaking wet!!! keep your ideas to your self:mad:

[little rowe boat]

Go try pointing that 2.5 at nothing, and side-step in front of a wall. Lean into it though... It will be dramatic.
I have the nozzle pressure remains the same. Believe me to hold a 2.5", you need to lean into it
The same thing happens exactly the same way with a garden hose. To test, run the hose at full blast and hold it back far enough on the hose to where the pressure coming out of it is supporting it up, but not far enough back where it is flopping around. Then put a piece of wood in front of it about 1-2'. The hose starts flopping all around wildly after taking a huge lurch backwards.
This doesn't matter you obviously have alot more expertise.:rolleyes:

[wright27]

Well when I am peeing on a wall, if I stand 4 feet back or 1 foot away the force is the same, but the splatter affect changes drastically.:D

[snake321]

Next time you better stand far away to avoid that 10% splashback :)
It really doesn't matter.
They weren't my shoes....

[Some Kind Of Monster]

But, we are talking water and not air... Water does not compress... so it doesn't matter if the hose is 10 feet from the wall or spraying down the driveway, the force felt by the firefighters would be the same.
It may not matter at 10 feet but what about 10 inches? Or a couple inches? It matters.

[Some Kind Of Monster]

I have held many fire hoses on the drill grounds and on actual fires and there is no difference in the resistance or nozzle pressure that you feel, while holding the line.. It does not make a difference if you are firing down a drive way or at a wall. The nozzle pressure stays the same. The velocity of the water lessens the further away from the nozzle it travels. The water does have more velocity at the end of the nozzle and it decreases as it meets the forces working against it after it leaves the nozzle, gravity, wind, the friction of the air.( this is usually called point of breakover)
I have held a 2.5" hose line flowing 200 gpm at 100 psi nozzle pressure, pointing it straight up overhead, side to side and straight down at the ground.( When I came on the job this was part of our 1st 6 months probationary requirement) The nozzle pressure remains the same. No difference.
Have you held that fokker 6 inches from a wall after side stepping into it like Froggy said?

[Sleek-Jet]

It may not matter at 10 feet but what about 10 inches? Or a couple inches? It matters.
The question said 10 feet.... it said nothing about 1" or 6" or .01"...

[Rexone]

Well when I am peeing on a wall, if I stand 4 feet back or 1 foot away the force is the same, but the splatter affect changes drastically.:D
I always pee on the weeds. Then the dogs do a follow up to make sure I got adequate coverage. Saves on Roundup.

[little rowe boat]

Have you held that fokker 6 inches from a wall after side stepping into it like Froggy said?
How about 6" off of the ground, pointing straight down at the ground? 100 psi nozzle pressure is 100 psi nozzle pressure.A 2.5" hose line flowing 200 gpm at 100 psi nozzle pressure can be alot to handle. If the nozzle pressure were to change/ or be greater because I was pointing it at a wall or even the ground 6" away then it should lift an average size person off of the ground. Which it does not.
How about advancing an 1.5" hose line into a structure which flows about 100 gpm at 100 psi nozzle pressure. There is very little visibility, but you can see fire through the smoke, so you open up the line and advance toward the fire, which is rolling up a wall and starting to lap overhead, as I advance toward the fire/wall the pressure on the nozzle is not getting any greater or when I point the nozzle at the ceiling which is directly overhead a few feet at most. The pressure does not get any greater. I have used the water velocity in a hose line to bring down drywall, which has to be done at a relatively close range because the water velocity at the end of the nozzle is greater than say 10' or 20' away but the nozzle pressure remains the same.

[little rowe boat]

Your post here reminds me of Cal Naughton Junior from "Talledega Nights" when the kid says "My teacher asked me what the capitol of North Carolina was and I said Washington D.C." and Cal said "Bingo!"
:D
Sorry, I never saw the movie.:)

[Some Kind Of Monster]

The question said 10 feet.... it said nothing about 1" or 6" or .01"...
Read the rest of my posts :rolleyes: :rolleyes: :rolleyes:
The answer is no,
However, does the force increase if the hose becomes say, inches from the wall? For example it would be impossible for the firemen to make that hose nozzle touch the wall.
Good job of ruling that out of the question though. You deserve a sucker. :idea:
This is true. Very interesting. I have a battery powered heli that will only hover up to a foot off the ground when the battery gets low. :idea: I would argue that at 10 feet the wall makes little or no difference, but get closer??

[Froggystyle]

This doesn't matter you obviously have alot more expertise.:rolleyes:
Trying to figure out which qualifies me more... the two years spent as an explorer scout at the Valley of the Moon Fire department or the subsequent years spent as a volunteer there. Wait, it could have been the major increase in resistance doing the seven minute hose lays that really brought it home...
Wait... I know... I think the thing that really set it in my head, was the drill we did while venting a doorway with a hose and was instructed to mind hitting the wall as it will knock you back in your boots...
One of them anyway...
I honestly think it had more to do with the air pressure in the cone then water pressure myself.