# Velocity

The flow of a gas-liquid multiphase system may cause erosion if velocities are high. This article presents an empirical relationship for estimating whether erosion will occur in a system at a certain velocity.

The transport of fluid under gravity is often achieved using partially filled pipes, channels, flumes, ditches and streams. To determine the slope and elevation change required or the flow rate that is achievable one must be able to calculate the head loss and friction factor. This article provides relationships for the calculation of head loss and friction factor for fluids flowing via these conduits.

This article presents Torricelliâ€™s law, a simplified method of estimating the velocity of fluid passing through an open orifice under static pressure.