# Illustration Bernoulli's principle applied to a flowing liquid

A liquid (e.g. water, blood) of density $$\rho$$ flows through a pipe. As an example, a cross-sectional area of the pipe is considered. The static pressure $$\mathit{\Pi}_{\text{s}}$$ acts on this area, which is at the height $$h$$ above the ground. The fluid moves through the cross-sectional area with the average flow velocity $$v$$.
Bernoulli's principle states that the flow velocity $$v$$ increases when the pressure $$\mathit{\Pi}_{\text{s}}$$ decreases and vice versa.