Calculator · Fluid Mechanics
Dynamic Pressure Calculator
The dynamic pressure is the pressure a moving fluid would gain if it were brought to rest without loss. It is not a pressure you can measure with a static tapping, and it is not the total pressure either.
Inputs
Water is about 1000 kg/m³; air at sea level is about 1.225 kg/m³.
Results
Dynamic pressure q = ½ρV²
| Fluid density ρ | 1000 kg/m³ |
|---|---|
| Speed V | 4 m/s |
| Dynamic pressure q | 8 kPa |
| Dynamic pressure q (kPa) | 8.0000 kPa |
| Velocity head V²/(2g) | 0.81577 m |
Assumptions
- · Incompressible flow; the speed magnitude is used.
Explore in the Lab
The velocity head is the same quantity divided by ρg.
Technical reference
q = ½ ρ V²
V = √(2q/ρ)
velocity head = α V² / (2g)
- q
- dynamic pressure of the moving fluid[Pa]
- ρ
- density of the fluid[kg/m³]
- V
- speed of the fluid relative to the body[m/s]
- g
- gravity, 9.80665 m/s²[m/s²]
Dynamic pressure is a kinetic-energy term, not a static pressure. Total pressure is the static pressure plus q, and only in incompressible frictionless flow.
The relation is incompressible. For a gas at high speed a compressibility correction is needed, and that is outside this V1 scope.
The velocity head is q/(ρg): the same physical quantity expressed as a height of the same fluid.