Find downstream speed from Bernoulli’s equation at constant height for an incompressible fluid.
| v₂ (m/s) | – |
Use this calculator when pressure and speed change along a streamline at the same height, such as a venturi, a tap, or a tank emptying through a nozzle. Height change, viscosity, and compressibility are ignored.
Along a streamline, P + ½ ρ v² stays constant. Solving for the downstream speed gives v₂ = √(v₁² + 2(P₁ − P₂)/ρ). If P₂ is too high for the upstream energy, there is no real v₂.
P₁ (Pa): Upstream static pressure, in pascals.
v₁ (m/s): Upstream speed. Use 0 for the free surface of a large tank.
P₂ (Pa): Downstream static pressure, in pascals.
Density (kg/m³): Fluid density. Fresh water ≈ 1000, air ≈ 1.2.
v₂ (m/s): Downstream speed from the constant-height Bernoulli relation.
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