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Fluid mechanics/heat transfer fundamentals: define the Reynolds number. Using symbols: ρ = density, V = characteristic velocity, l = characteristic length, μ = dynamic viscosity, ν = kinematic viscosity. Select the correct expression for the Reynolds number (Re).

Difficulty: Easy

Re = (ρ V l)/μ
Re = (μ V l)/ρ
Re = (k l)/h
Re = (ρ cᵖ V)/k

Correct Answer: Re = (ρ V l)/μ

Explanation:

DefinitionThe Reynolds number quantifies the ratio of inertial to viscous forces: Re = (ρ V l)/μ = V l/ν.

Why A is correctDimensions: [ρ]·[V]·[l]/[μ] → (kg·m⁻³)(m·s⁻¹)(m)/(kg·m⁻¹·s⁻¹) = 1 (dimensionless), as required.

Final AnswerRe = (ρ V l)/μ.

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