alan
can we have it english please?
A Venturi meter is shown in a diagram, the pressure in "1" conditions is higher than "2", and the relationship between the fluid speed in "2" and "1" respectively, is the same as for pressure.
A Venturi meter is shown in a diagram, the pressure in "1" conditions is higher than "2", and the relationship between the fluid speed in "2" and "1" respectively, is the same as for pressure.The Venturi effect is a special case of Bernoulli's principle, in the case of fluid or air flow through a tube or pipe with a constriction in it. The fluid must speed up in the restriction, reducing its pressure and producing a partial vacuum via the Bernoulli effect. It is named after Giovanni Battista Venturi, (1746–1822), an Italian physicist.
A fluid passing through smoothly varying constrictions is subject to changes in velocity and pressure in order to satisfy the conservation of mass-flux (flow rate). The reduction in pressure in the constriction can be understood by conservation of energy: the fluid (or gas) gains kinetic energy as it enters the constriction, and that energy is supplied by a pressure gradient force from behind. The pressure gradient reduces the pressure in the constriction, in reaction to the acceleration. Likewise, as the fluid leaves the constriction, it is slowed by a pressure gradient force that raises the pressure back to the ambient level.
The limiting case of the Venturi effect is choked flow, in which a constriction in a pipe or channel limits the total flow rate through the channel, because the pressure cannot drop below zero in the constriction. Choked flow is used to control the delivery rate of water and other fluids through spigots and other valves.
In the diagram shown abovet, using Bernoulli's equation in the special case of incompressible fluids (such as the approximation of a water jet), the theoritecal maximum pressure drop in the constriction would be given by (ρ/2)(v12 - v22). For example, for seawater ρ = 1.023 g /cc; 1.5 inch diameter pipe with a 0.25 inch restriction flowing 5 gpm; v at the pipe is 28 cm/sec; v at the restriction would have to be 995 cm/sec; the pressure drop would be -51,000 Pascals or about ½ bar!
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