Definition - What does Energy Gradient mean?
The energy gradient is equal to the height of the velocity head (the velocity of a fluid expressed in terms of the static pressure required to produce that velocity) above the hydraulic gradient – the distance water free flows downward from a height. In both open and pipe flow, the decrease of energy gradient for a given length of channel or pipe represents the loss of energy by friction. the energy gradient reflects the loss of energy by friction and the conversions between potential and kinetic energy.
Trenchlesspedia explains Energy Gradient
For uniform flow, the hydraulic gradient and the energy gradient are parallel to each other, with the energy gradient above the hydraulic gradient a distance equal to the height of the velocity. The hydraulic gradient is adequate to determine friction loss, since no potential energy is converted to kinetic energy. In accelerated flow, such as that from the outfall of a pump, the hydraulic gradient is steeper than the energy gradient, and in retarded flow – such as that caused by treatment plant baffles – the energy gradient is steeper than the hydraulic gradient. To properly analyze flow under either of these editions, consider both the energy gradient in the hydraulic gradient.