Fluid Dynamics (Bernoulli) Calculator

Bernoulli's equation alone has more unknowns (pressure, velocity, and height at point 2) than equations to solve them with, so a unique answer requires an assumption about which quantity stays fixed. The calculator reports pressure2SameV (assuming velocity is unchanged, useful for a constant-diameter pipe with an elevation change) and two velocity scenarios — one holding pressure constant and one assuming point 2 is open to atmosphere — rather than picking one assumption for you.

It's the velocity at point 2 if that point is open to atmospheric pressure (zero gauge pressure), computed from the full Bernoulli balance of point 1's pressure, velocity, and height difference. This is the classic Torricelli-type scenario — for example, fluid exiting a tank into open air — where the exit velocity depends on the driving pressure and elevation head rather than a fixed downstream pressure.

These three values decompose point 1's total energy per unit volume into its parts: static pressure is the input pressure directly, dynamic pressure (½ρv²) represents kinetic energy from the fluid's motion, and hydrostatic pressure (ρgh) represents potential energy from elevation. Comparing their magnitudes shows which effect dominates the flow at that point — for example, at low velocity in a tall tank, hydrostatic pressure will dwarf the dynamic term.

Bernoulli's equation assumes an ideal fluid — incompressible, non-viscous, and flowing steadily along a single streamline with no pumps, turbines, or friction losses between the two points. Real piping systems lose energy to wall friction, fittings, and turbulence, so actual pressures and velocities will be somewhat lower than this frictionless, ideal-case calculation predicts, especially over longer runs of pipe.