Notation in fluid dynamics: A circle with a horizontal bar inside

AI Thread Summary
The notation of a circle with a horizontal bar inside, encountered in discussions of the Venturi effect, represents the distinction between measured values and actual physical quantities due to measurement interference. This notation indicates that the pressure measurement affects the values of temperature, pressure, molar mass, density, and concentration in the fluid. The confusion arises from the way these quantities are presented in literature, particularly in the context of pressure-based meters. Additional resources, such as an engineering article on pressure-temperature compensation, may provide further clarity on this topic. Understanding this notation is crucial for accurate interpretation in fluid dynamics.
Leo Liu
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I came across this notation when reading the wiki article on Venturi effect, which baffled me. Can someone please tell me its meaning?
 
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It is actually explained in a confusing way. The act of pressure measurement itself is interfering with the actual values of temperature T, pressure P, molar mass Μ, density ρ and concentration C of the liquid. Hence these physical quantities around the pressure-based meter have different values which are denoted with this "funny" notation.
 
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