1. What is Reynolds Number?

The Reynolds number (Re) is a dimensionless quantity used in fluid mechanics to predict flow patterns in different fluid flow situations. It compares inertial forces to viscous forces and helps determine whether flow will be laminar or turbulent.

2. How Does the Calculator Work?

The calculator uses the Reynolds Number equation for US units:

Where:

• \( Re \) — Reynolds number (dimensionless)
• \( v \) — Velocity (ft/s)
• \( d \) — Diameter (in)
• \( \nu \) — Kinematic viscosity (cSt)

Explanation: The equation accounts for the relationship between flow velocity, characteristic length (diameter), and fluid properties (viscosity).

3. Importance of Reynolds Number

Details: Reynolds number is crucial for determining flow regime (laminar, transitional, or turbulent), designing piping systems, calculating friction factors, and predicting heat transfer coefficients.

4. Using the Calculator

Tips: Enter velocity in ft/s, diameter in inches, and kinematic viscosity in centistokes (cSt). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the significance of 7745.8 in the equation?
A: This is a conversion factor that accounts for the US units (ft/s, in, cSt) to make the Reynolds number dimensionless.

Q2: What are typical Reynolds number ranges?
A: Laminar flow: Re < 2300, Transitional: 2300 < Re < 4000, Turbulent: Re > 4000 for pipe flow.

Q3: When should I use this calculator?
A: For internal pipe flow calculations with Newtonian fluids in US customary units.

Q4: Are there limitations to this equation?
A: This form is specific to US units. For SI units, a different form is used. Also assumes circular pipe cross-section.

Q5: How does viscosity affect Reynolds number?
A: Higher viscosity (ν) decreases Re, making laminar flow more likely. Lower viscosity increases Re, favoring turbulent flow.