Static Fluid Pressure

The pressure in a static fluid arises from the weight of the fluid and is given by the expression

The pressure from the weight of a column of liquid of area A and height h is

The most remarkable thing about this expression is what it does not include. The fluid pressure at a given depth does not depend upon the total mass or total volume of the liquid. The above pressure expression is easy to see for the straight, unobstructed column, but not obvious for the cases of different geometry which are shown.

Because of the ease of visualizing a column height of a known liquid, it has become common practice to state all kinds of pressures in column height units, like mmHg or cm H₂O, etc. Pressures are often measured by manometers in terms of a liquid column height.

Fluid Pressure Calculation

Discussion 讨论

Fluid column height in the relationship is often used for the measurement of pressure. After entering the relevant data, any one of the highlighted quantities below can be calculated by clicking on it. Pressure difference = density x g x height 压强差 = 密度 × g × 高度 If the fluid density is ρ = gm/cm3 = kg/m3 and the column height is h = m = x 10^ m h = ft then the pressure difference is ΔP = kPa ΔP = lb/in2 ΔP = mmHg= inches Hg ΔP = atmos ΔP = inches water= cm water 在关系中，流体柱的高度常用于压力的测量。输入相关数据后，点击下面突出显示的任一量即可计算。如果流体密度是ρ = gm/cm³ = kg/m³，而柱高是h = m = ×10^m h = ft，那么压力差是ΔP = kPa ΔP = lb/in² ΔP = mmHg= inches Hg ΔP = atmos ΔP = inches water= cm water 中文译文中的待填/计算数值依次对应：1：d 2：dk 3：h 4：hb 5：hp 6：hc 7：pk 8：pc 9：pm 10：pmc 11：pa 12：piw 13：pcw。实际数值以上方原输入框为准。

Note that this static fluid pressure is dependent on density and depth only; it is independent of total mass, weight, volume, etc. of the fluid.