228
P. Liu
Kj
K
Fr 1 of section before jump
Fig. 3.53 Relationship between hydraulic jump energy dissipation efficiency and
Froude number of cross section before jump
3.6 Unsteady Flow in a Pressure Pipeline
3.6.1 Overview
The unsteady flow of pressurized pipeline widely appears in water conservancy and hydropower, irrigation and water supply, energy and chemical
engineering, hydraulic transmission, and other projects, such as the pressurized water delivery system of hydropower station and pump station, water
supply pipe network, cooling water system of fire and nuclear power station,
natural gas and oil transportation pipeline, hydraulic device pipeline system,
etc. According to the time-varying speed of the hydraulic elements in the
pipeline, the unsteady flow in the pressurized pipeline can be divided into
water oscillation flow and water hammer phenomenon. If the water in the
pipeline is incompressible and the hydraulic elements change slowly with
time, it is called water oscillation flow, which is common in the water level of
U-shaped pipeline and the water level fluctuation of the pressure regulating
system of hydropower station, as shown in Figs. 3.54 and 3.55. Otherwise, the water is compressible, and the hydraulic elements change violently
with time, resulting in the evolution of water flow in the pipeline in the
form of pressure wave, which is called water hammer. This kind of situation often occurs in the pressure pipeline system. The working state of the
flow passage element of the pipeline changes suddenly, which makes the
P. Liu
Kj
K
Fr 1 of section before jump
Fig. 3.53 Relationship between hydraulic jump energy dissipation efficiency and
Froude number of cross section before jump
3.6 Unsteady Flow in a Pressure Pipeline
3.6.1 Overview
The unsteady flow of pressurized pipeline widely appears in water conservancy and hydropower, irrigation and water supply, energy and chemical
engineering, hydraulic transmission, and other projects, such as the pressurized water delivery system of hydropower station and pump station, water
supply pipe network, cooling water system of fire and nuclear power station,
natural gas and oil transportation pipeline, hydraulic device pipeline system,
etc. According to the time-varying speed of the hydraulic elements in the
pipeline, the unsteady flow in the pressurized pipeline can be divided into
water oscillation flow and water hammer phenomenon. If the water in the
pipeline is incompressible and the hydraulic elements change slowly with
time, it is called water oscillation flow, which is common in the water level of
U-shaped pipeline and the water level fluctuation of the pressure regulating
system of hydropower station, as shown in Figs. 3.54 and 3.55. Otherwise, the water is compressible, and the hydraulic elements change violently
with time, resulting in the evolution of water flow in the pipeline in the
form of pressure wave, which is called water hammer. This kind of situation often occurs in the pressure pipeline system. The working state of the
flow passage element of the pipeline changes suddenly, which makes the