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Velocity Head
Dynamic pressure and velocity head
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Dynamic pressure in a fluid flow can be expressed as
pd = ρf v2 / 2 (1)
where
pd = dynamic pressure in fluid (Pa, psi)
ρf = density of fluid (kg/m3, lb/ft3)
v = fluid velocity (m/s, ft/s)
Head water column can be calculated by dividing dynamic pressure with specific weight of water like
hw = pd / γw
= (ρf v2/2) / ρw g
= ρf v2/ 2 g (2)
where
hw = head water (m Water, ft Water)
γw = ρw g = specific weight water
where
ρw = density of water (kg/m3, lb/ft3)
g = acceleration of gravity (32.174 ft/s2, 9.81 m/s2)
Air Flow - Velocity and Dynamic Head Chart
Charts based on air density 1.205 kg/m3 and water density 1000 kg/m3.
Water Flow - Velocity and Dynamic Head Chart
Heads at different velocities are indicated in the table below:
| Velocity - v - (ft/sec) | Velocity Head - v2/2g - (ft Water) |
| 0.5 | 0.004 |
| 1.0 | 0.016 |
| 1.5 | 0035 |
| 2.0 | 0.062 |
| 2.5 | 0.097 |
| 3.0 | 0.140 |
| 3.5 | 0.190 |
| 4.0 | 0.248 |
| 4.5 | 0.314 |
| 5.0 | 0.389 |
| 5.5 | 0.470 |
| 6.0 | 0.560 |
| 6.5 | 0.657 |
| 7.0 | 0.762 |
| 7.5 | 0.875 |
| 8.0 | 0.995 |
| 8.5 | 1.123 |
| 9.0 | 1.259 |
| 9.5 | 1.403 |
| 10.0 | 1.555 |
| 11.0 | 1.881 |
| 12.0 | 2.239 |
| 13.0 | 2.627 |
| 14.0 | 3.047 |
| 15.0 | 3.498 |
| 16.0 | 3.980 |
| 17.0 | 4.493 |
| 18.0 | 5.037 |
| 19.0 | 5.613 |
| 20.0 | 6.219 |
| 21.0 | 6.856 |
| 22.0 | 7.525 |
- 1 ft (foot) = 0.3048 m = 12 inches = 0.3333 yd
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Related Topics
- Fluid Mechanics - The study of fluids - liquids and gases. Involves various properties of the fluid, such as velocity, pressure, density and temperature, as functions of space and time.
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Related Documents
- Pitot Tubes - Pitot tubes can be used to indicate fluid flow velocity by measuring the difference between the static and dynamic pressures in fluids
- Static Pressure and Pressure Head in Fluids - Static pressure and pressure head
- Total Pressure or Head Loss in Pipe or Duct Systems - Major and minor loss in pipe, tubes and duct systems
