External mouthpiece: pressure at vena contracta relative to atmosphere In a free-discharging external mouthpiece, the absolute pressure head at the vena contracta is ____ the atmospheric pressure head by approximately 0.89 times the height of liquid above the vena contracta. Choose the correct completion.
Mechanical Engineering
Hydraulics and Fluid Mechanics
Difficulty: Medium
Choose an option
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Aequal to
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Bgreater than
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Cless than
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Dindependent of
Answer
Correct Answer: less than
Explanation
Concept/Approach
- At the vena contracta of an external mouthpiece, the jet accelerates and the static pressure drops below atmospheric. Experiments show the pressure deficit is about 0.89h, where h is the liquid height above the vena contracta.
Final Answerless than