Knowledge points of the relationship between fluid pressure and flow velocity

The knowledge points of the relationship between fluid pressure and flow rate are as follows:

When the velocity of the fluid increases, the pressure on the interface between the object and the fluid decreases, and vice versa. To commemorate this scientist's contribution, this discovery is called "Bernoulli effect". Bernoulli effect is applicable to all fluids, including gas, and it is one of the basic phenomena when the fluid flows stably, reflecting the relationship between the pressure and flow rate of the fluid.

P+ 1/2ρv2+ρgh=C, which is the so-called Bernoulli equation. Where p is the pressure at a certain point in the fluid, v is the velocity of the fluid at that point, p is the density of the fluid, g is the acceleration of gravity, h is the height of that point, and c is a constant. Bernoulli equation reflects the relationship between speed and pressure. The greater the fluid velocity, the smaller the pressure, and the smaller the fluid velocity, the greater the pressure.

Bernoulli equation can also be expressed as p1+1/2pv12+pgh1= p2+1/2ρ v22+pgh2. This is the basic principle adopted by hydraulics before the establishment of the theoretical equation of fluid mechanics continuum, and its essence is the conservation of fluid mechanical energy. Namely: kinetic energy+gravitational potential energy+pressure potential energy = constant. Its most famous inference is that when the flow rate is constant, the pressure will be low when the flow rate is high.

Because Bernoulli equation is derived from the conservation of mechanical energy, it is only applicable to ideal fluids with negligible viscosity and incompressibility. Bernoulli theorem is widely used in hydraulics and applied fluid mechanics. Moreover, because it is a finite relationship, it is often used to replace the differential equation of motion, so it is also of great significance in the theoretical study of fluid mechanics.

Expression of fluid pressure:

Pressure can be expressed and measured by different standards. For example, the pressure measured based on absolute vacuum (that is, zero atmospheric pressure) is called absolute pressure, which is the real pressure of the fluid. Pressure measured based on local atmospheric pressure is called gauge pressure or vacuum degree.

When the absolute pressure of the measured fluid is greater than the external atmospheric pressure, the pressure measuring instrument used is called a pressure gauge. The reading on the pressure gauge shows that the absolute pressure of the measured fluid is m higher than the local atmospheric pressure, which is called gauge pressure.