Calculate velocity from pressure: enter dynamic (velocity) pressure in Pa, psi or inH₂O and pick air or water to get flow speed, or solve the reverse.
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Pressure to Velocity Formula
The following formula is used to calculate a velocity from dynamic pressure.
- Where V is the velocity (m/s)
- q is the dynamic pressure (pascals)
- p is the fluid mass density (kg/m^3)
To calculate velocity from pressure, multiply the dynamic pressure by 2, divide by the fluid mass density, then take the square root of that result.
| Dynamic Pressure (Pa) | Velocity (m/s) |
|---|---|
| 10 | 0.141 |
| 20 | 0.200 |
| 50 | 0.316 |
| 100 | 0.447 |
| 200 | 0.632 |
| 300 | 0.775 |
| 400 | 0.894 |
| 500 | 1.000 |
| 750 | 1.225 |
| 1000 | 1.414 |
| 1500 | 1.732 |
| 2000 | 2.000 |
| 3000 | 2.449 |
| 4000 | 2.828 |
| 5000 | 3.162 |
| 7500 | 3.873 |
| 10000 | 4.472 |
| 15000 | 5.477 |
| 20000 | 6.325 |
| 50000 | 10.000 |
| * Rounded to 3 decimals. Assumes fluid density ρ = 1000 kg/m³ (water). Formula: v = √(2q/ρ). Units: q in pascals (Pa), v in meters per second (m/s). | |
Pressure to Velocity Definition
Calculating a velocity from a dynamic pressure requires that you also know the density. Dynamic pressure arises from the movement of fluid through a volume.
Pressure to Velocity Example
How to calculate velocity from pressure?
The first step in calculating a velocity from pressure is to determine or measure the dynamic pressure that happens as a result of the fluid flow through the pipe.
In this example, the dynamic pressure is found to be 200 pascals.
The next step is to determine the density of the fluid. In this case, the density is measured to be 1.225 kg/m^3.
Finally, calculate the velocity from the dynamic pressure and density using the formula above:
V = Sqrt [ (2*q/p) ]
V = Sqrt [ (2*200/1.225) ]
V = 18.07 m/s.
FAQ
What is dynamic pressure?
Dynamic pressure is q = ½ρv². Under suitable incompressible measurement conditions, it equals total pressure minus static pressure.
What is the relationship between pressure and velocity in fluid dynamics?
Bernoulli’s equation describes the relationship between pressure and velocity in fluid dynamics.
For steady incompressible flow along a streamline, static pressure, kinetic energy per unit volume and elevation energy balance when pumps and losses are absent.
How does pressure change with velocity in a fluid?
Static pressure is not inversely proportional to velocity. At constant density, dynamic pressure is proportional to velocity squared.
At equal elevation and constant total pressure in the ideal model, increasing speed reduces static pressure. Dynamic pressure increases with speed.
What is Bernoulli’s equation used for?
Bernoulli’s equation describes the relationship between pressure, velocity, and height in a fluid flow system.
It is commonly used in various fields such as aerodynamics, hydrodynamics, and mechanics to analyze the flow of fluids.
Why does the pressure decrease with velocity in a fluid flow?
For ideal flow at equal elevation and constant total pressure, static pressure decreases as speed increases.
Elevation changes, pumps, friction and compressibility can change this relationship.
What is the difference between dynamic pressure and static pressure?
Dynamic pressure is the kinetic energy per unit volume associated with fluid motion. Static pressure is the local thermodynamic pressure and exists in moving fluids as well as fluids at rest.
Dynamic pressure is proportional to density and speed squared. Static pressure depends on the flow and boundary conditions; density and height alone describe only a specified hydrostatic pressure difference.
How is pressure affected by the velocity of a fluid?
The velocity of a fluid affects pressure by changing the dynamic pressure of the fluid.
Increasing speed raises dynamic pressure at fixed density. A corresponding static-pressure decrease requires the stated ideal-flow conditions.
What is the effect of temperature on the pressure in a fluid?
Temperature can affect density and pressure; the relationship depends on the fluid, constraints and thermodynamic process.
There is no universal rule that heating a fluid reduces its pressure. For an ideal gas in a rigid closed volume, heating increases pressure.
At fixed pressure an ideal gas expands when heated; liquid behavior also depends on thermal expansion and confinement.
How does fluid velocity affect the pressure drop in a pipe?
Pipe friction loss depends on geometry, roughness, density, viscosity and flow regime. Dynamic pressure alone is not the inlet-to-outlet pipe pressure drop.
At otherwise fixed conditions, greater flow generally increases frictional pressure loss; a pipe-flow model is needed to quantify it.
How does the viscosity of a fluid affect the relationship between pressure and velocity?
Viscosity produces flow resistance and affects the Reynolds number and friction factor.
At a specified flow rate, higher viscosity can require a larger pressure difference. At a specified pressure difference, it can reduce flow; no universal absolute-pressure comparison follows.
