Bernoulli Pressure LoweringThe linear drop in fluid pressure is according to Poiseuille's law, but the constriction produces and extra drop in pressure according to the Bernoulli Principle.
The liquid column height is a measure of the fluid pressure at that point in the flow tube. The vertical tubes act as manometers. The manometers show that the pressure is lowered at the constriction relative to what it would have been in a uniform tube. The pressure that drives the fluid through the tube is the static fluid pressure at the bottom of the reservoir. The resistance to flow represented by the tube causes a drop in pressure as you proceed along the tube.
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Index Bernoulli concepts | ||||||||
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Pressure Drop with LengthThe pressure drop as fluid flows from a container can be modeled by Poiseuille's law. The drop in fluid pressure is indicated by the liquid column heights.
The liquid column height is a measure of the fluid pressure at that point in the flow tube. The vertical tubes act as manometers.The pressure that drives the fluid through the tube is the static fluid pressure at the bottom of the reservoir. The resistance to flow represented by the tube causes a drop in pressure as you proceed along the tube. The pressure drop illustrated suggests that the tube continues for some distance to the right, and you could project the line of pressure drop to imply the location of the end of the tube. At the open end of the tube, you would imply that the gauge pressure is zero, implying that the only pressure on the fluid is atmospheric pressure. |
Index Poiseuilles law concepts | |||
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Pressure Monitoring for a Constricted TubeThis is a direct experimental observation of the Bernoulli effect. A high pressure air supply directs air through a glass tube which has a constriction about halfway along it. Pressure is indicated by three manometers in which the liquid level is a measure of the pressure above the liquid. The fact that the pressure in the tube past the constriction is slightly lower than the pressure before the constriction is a demonstration of fluid friction. This can be modeled by Poiseuille's law. |
Index Poiseuilles law concepts Bernoulli concepts | ||
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