This model illustrates the principles of motion of an ideal incompressible liquid in a horizontal tube of variable cross-section. The hydrostatic pressure in the liquid is measured with manometric pipes that are located throughout the tube. |
Modify the diameters of the tube's segments, and observe the changes in the speed of the flow and in liquid pressure. Note that the pressure of the liquid is relatively greater in those regions of the tube where the flow speed is relatively smaller. This phenomenon is a direct consequence of Bernoulli's equation:
1/2ρv2 + ρgH + P = const
Bernoulli's equation is founded on the principles of energy conservation. The law of energy conservation is applied to a steady flow of an ideal (i.e. non-viscous) incompressible liquid.
Here, ρ is the density of the liquid, v is the velocity of the flow, H is the height of the observation point and P is the pressure at this point of the flow.
For a horizontal where pipe H = const, Bernoulli's equation assumes the following form:
1/2ρv2 + P = const
Therefore, the pressure of a liquid diminishes at those locations where the velocity of the flow is greater.