What do dynamic pressure energy and static pressure energy mean?

This post was last edited by yunzhongzi112 on 2011-8-22 20:57: the flow rate increases while the pressure decreases. A simple example is a household faucet: the greater the pressure in the water supply pipeline, the higher the flow rate of water when it emerges from the faucet, and thus the greater the dynamic head. But the pressure is very low, at atmospheric pressure; in other words, the hydrostatic head is approximately zero

By creating a reduction in diameter at the pump outlet, that is, by making the diameter larger, the dynamic pressure energy decreases while the static pressure energy increases. This is generally done to reduce energy losses within the pipeline. When the diameter at the pump inlet is reduced, the dynamic pressure energy increases while the static pressure energy decreases

This post was last edited by yunzhongzi112 on 2011-8-22 at 20:58. Dynamic pressure energy is a function of velocity, while static pressure energy is a function of position. Similarly, as gravity does work, the object’s falling speed increases.

First, understand what dynamic pressure energy is and what static pressure energy is.

Dynamic pressure energy refers to the kinetic energy possessed by a fluid； Static pressure energy refers to the pressure potential energy possessed by a fluid ； Relevant discussions can be found in the following post: http://bbs.hcbbs.com/archiver/tid-515970.html

Dynamic pressure energy: (Kinetic energy) When a fluid moves at a certain speed, it possesses kinetic energy. Stagnation pressure: There is a certain stagnation pressure at any point within a stationary fluid. Any point within a flowing fluid also has a certain static pressure. For example, if a hole is made in the wall of a tube through which liquid flows, and this hole is connected to a vertical glass tube, the liquid will rise inside the glass tube. The height of the rising liquid column represents the static pressure of the flowing liquid at that cross-section. Since the liquid at this section has a certain pressure, work must be done on the fluid to overcome this pressure in order to push it into the system. Therefore, the fluid passing through the cross-section must enter the system with energy equivalent to the required work, and this energy possessed by the fluid is known as static pressure energy or kinetic energy. In the steady flow of an ideal fluid through a pipe with no external work input, the sum of the potential energy, kinetic energy, and static pressure energy per unit mass of fluid at any cross-section remains constant; this value is known as the total mechanical energy. Therefore, in the steady flow of an ideal fluid in a horizontal pipe, if the cross-sectional area of the pipe decreases at some point, the flow velocity increases and the kinetic energy increases as well. Since the total mechanical energy remains constant, the static pressure energy must decrease accordingly; that is, part of the static pressure energy is converted into kinetic energy, and vice versa.

Generally, ignoring energy losses, the total mechanical energy is equal to the dynamic pressure energy + static pressure energy + potential energy, with these three forms of energy converting into one another

Reply 1# sxf1028102800: Dynamic pressure energy is a function of velocity, while static pressure energy is a function of position

Reply to 10# loislrh: Hydrostatic energy has nothing to do with position, while potential energy is related to position!