The Venturi effect is the rop in fluid pressure that results when an incompressible fluid flows through a constricted section of pipe. The Venturi effect may be derived from a combination of Bernoulli's principle and the equation of continuity. The fluid velocity must increase through the constriction to satisfy the equation of continuity, while its pressure must decrease due to conservation of energy: the gain in kinetic energy is supplied by a drop in pressure or a pressure gradient force.