1. What is Reynolds Number?

The Reynolds number (Re) is a dimensionless quantity used to predict flow patterns in different fluid flow situations. It represents the ratio of 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:

Where:

• \( \rho \) — Density of the fluid (kg/m³)
• \( v \) — Velocity of the fluid relative to the object (m/s)
• \( L \) — Characteristic linear dimension (m)
• \( \mu \) — Dynamic viscosity of the fluid (Pa·s)

Explanation: The equation compares the relative importance of inertial forces (numerator) to viscous forces (denominator) in fluid flow.

3. Importance of Reynolds Number

Details: Reynolds number is crucial in fluid dynamics to determine flow regimes:

• Re < 2000: Laminar flow
• 2000 < Re < 4000: Transitional flow
• Re > 4000: Turbulent flow

4. Using the Calculator

Tips: Enter all values in consistent SI units (kg/m³ for density, m/s for velocity, m for length, and Pa·s for viscosity). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is characteristic length?
A: For pipes, it's typically the diameter. For objects in flow, it's often the length in flow direction.

Q2: What are typical viscosity values?
A: Water at 20°C: ~0.001 Pa·s, Air at 20°C: ~0.000018 Pa·s, Honey: ~2-10 Pa·s.

Q3: How does temperature affect Re?
A: Temperature changes viscosity (μ), which directly affects Re. Higher temperature generally decreases μ for liquids.

Q4: Can Re be used for compressible flow?
A: The basic Re calculation is for incompressible flow. Modified versions exist for compressible flow.

Q5: What's the practical significance of Re?
A: It's used in designing pipes, aircraft, ships, and predicting weather patterns, among many other applications.