Red vs Re: Clarifying an Equation Mystery

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SUMMARY

Re[SIZE="1"]d and Re refer to the Reynolds number, a dimensionless quantity used in fluid mechanics to predict flow patterns. The subscript "d" in Re[SIZE="1"]d indicates that the Reynolds number is calculated with respect to a specific characteristic dimension, such as diameter in pipe flow scenarios. In contrast, Re without a subscript may refer to a general Reynolds number applicable to various geometries. Understanding these distinctions is crucial for accurately analyzing fluid dynamics in different contexts.

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Kenny Lee
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Hi, this is going to sound very stupid.
Is Red the same as Re?
Its just that in some equations, I have Red, and then in others Re. It might not sound like much of a problem, but I'd really appreciate if someone could clear things up for me. Thanks!
 
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Reynolds number with a subscript usually pertains to the RE with respect to a particular characteristic dimension of an object. For example, in a lot of problems looking at flows past flat plates, you will see [tex]RE_x[/tex] for the RE along the length of the plate measured from the leading edge of the plate. Perhaps the usage in your case is the flow past a cylinder or sphere.
 
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ohh right. Diameter, that's what it stands for. Its pipe flow. Thanks!
 

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