Hydrostatic Pressure

Bob Gagnon plumbing and heating

Can someone tell me what hydrostatic pressure would be exerted on the walls of a tank per foot of water height?

Thanks, Bob Gagnon

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bob_46

?

2.31 psi

Unknown

bob

Be careful here ;-),
1 PSI pressure will push water up vertically 2.31 feet.

Dave

bob_46

Duh

I should have said 1/2.31. Thanks Dave.

scrook_2

but

The hydrostatic pressure of the water an any point is the same regardless of directon, otherwise the water would flow from higher pressure to lower within the tank.

A tank with say 46.2' of water in it will, at a point 23.1 ft below the surface, see 10 psi of pressure on its wall; at the bottom (46.2' from the surface) 20 psi, at the top (0') 0 psi. etc.

1 psi only pushes the horizontal surface of the water vertically, if the vessel walls are not vertical the water also moves horizontally until it touches the walls!

Ron Gillen

On it's base

.433 PSI/foot of water on the base. Less as you move up the walls.

The Boiler Dr.

Wouldn't hydrostic pressure

also be determined by the size of the vessel - height and width - multiplied by the weight of the liquid

Unknown

hydrostic pressure

Width wouldn`t matter, only the height.
Depending on your sea-level of course ;-).
A divers depth gauge is the same on both sides of a lake.

Dave

The Boiler Dr.

What I was referring to

was that depending on the volume (cu ft/in)of the vessel the weight of the fluid would generate a greater hydrostatic pressure ... not?

Unknown

Not really,

speaking of water here,, it`s the added pressure we put on top of it that will add to the hydrostatic pressure below.

Dave

jp_2

think at extremes

sometime helps.

if a pool were 1 inch high and 1 inch wide, think of pressure against the wall.

now make that pool 1 inch high and a mile wide, pressure at bottom of both pools the same.

if you stood in both pools, does it make sense that you could feel different pressures on your feet?

Bob Gagnon plumbing and heating

Hydrostatic Pressure

Is that the pressure of water not moving. I am dealing with the local hydro plant operators and the height of the river above the height of the partially blocked intake pipes. Wouldn't that be fluid pressure because the water is moving? That may be harder to figure with flows and all, but if it were not moving a two foot difference in height would exert 4.62 psi on the sides of a vessel?

Thanks, Bob Gagnon

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Jamie Hall

Hydrostatic pressure

is determined solely by the density of the fluid and the height of the fluid above the point.

Now... if the fluid is moving, interesting things happen, and it can get really complicated. However, if the fluid is moving at a constant velocity, the pressure is the hydrostatic pressure. If you change the velocity, however, that's when it gets interesting. In open channel flow, say a steeper or shallower channel, or in full pipe flow, a larger or smaller diameter pipe, the static pressure will change to keep the total energy of the moving fluid constant. In open channel flow this shows up as a change in the depth of the water, for instance. Another way to change the velocity is to change the direction of flow without change the speed. Then a considerable pressure is found in the area where the direction of flow is changing -- say at a bend in a river, or in an elbow on a pipe. This pressure comes about because a force is required on the fluid to make it change direction (a change in momentum requires a force operating over time).

Can get messy...