Does the discharge coefficient of an injector depend on the fluid?

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SUMMARY

The discharge coefficient, defined as the ratio of actual discharge to ideal discharge, is influenced by the orifice shape and the fluid Reynolds number. For instance, a rounded inlet orifice can achieve a discharge coefficient close to 1.0, while a square edge inlet orifice typically has a coefficient of approximately 0.61 at high Reynolds numbers. The discharge coefficient is not constant across all incompressible fluids; it varies based on fluid density and the specific characteristics of the orifice. Therefore, experimental measurements of the discharge coefficient using water will yield different values for other fluids.

PREREQUISITES
  • Understanding of discharge coefficient and its significance in fluid dynamics
  • Familiarity with orifice design and its impact on flow characteristics
  • Knowledge of Reynolds number and its role in fluid flow analysis
  • Basic principles of fluid density and its effect on discharge measurements
NEXT STEPS
  • Research "orifice discharge coefficient" to understand its calculation and applications
  • Study "Reynolds number" and its implications in fluid mechanics
  • Explore experimental methods for measuring discharge coefficients in various fluids
  • Investigate the impact of fluid density on discharge coefficients in practical scenarios
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Fluid dynamics engineers, mechanical engineers, and researchers involved in flow measurement and orifice design will benefit from this discussion.

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TL;DR
If one were to experimentally measure the discharge coefficient using water, would this value be constant for all incompressible fluids?
The discharge coefficient is the ratio of the actual discharge to the ideal discharge and can be measured experimentally. If one were to experimentally measure the discharge coefficient using water, would this value be constant for all incompressible fluids?

What does the discharge coefficient depend on, and is it unique to every fluid?
 
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The discharge coefficient is a function of the shape of the orifice and the fluid Reynolds number. An orifice with rounded inlet will have a discharge coefficient approaching 1.0, an orifice with a perfect square edge inlet will have the coefficient approximately 0.61 at high Reynolds numbers. Good search terms to learn more are orifice discharge coefficient and reynolds number. The image below shows the relationship between the discharge coefficient of a square edge orifice with the Reynolds number:
Discharge coefficient.jpg

The discharge coefficient of a specific orifice is unique to the exact shape of the orifice and the Reynolds number.
 
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