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:

Where:

• \( \rho \) — Fluid density (kg/m³)
• \( v \) — Flow velocity (m/s)
• \( d \) — Characteristic length (m)
• \( \mu \) — Dynamic viscosity (Pa·s)

Explanation: The equation shows the ratio of inertial forces (ρv) to viscous forces (μ/d). Higher values indicate more turbulent flow.

3. Importance of Reynolds Number

Details: Reynolds number is crucial for predicting flow regimes, designing piping systems, calculating drag coefficients, and modeling fluid behavior in various engineering applications.

4. Using the Calculator

Tips: Enter all values in consistent SI units. For pipes, characteristic length is typically the diameter. For other geometries, use appropriate length scales.

5. Frequently Asked Questions (FAQ)

Q1: What are typical Reynolds number ranges?
A: Laminar flow: Re < 2300, Transitional: 2300 < Re < 4000, Turbulent: Re > 4000 (for pipe flow).

Q2: How does temperature affect Reynolds number?
A: Temperature changes viscosity (μ) and density (ρ), which both affect Re. Higher temperatures typically decrease μ more than ρ, increasing Re.

Q3: What's the characteristic length for non-pipe flows?
A: For open channels, use hydraulic radius. For objects in flow, use length parallel to flow direction.

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

Q5: What's the significance of critical Reynolds number?
A: It's the Re value at which flow transitions from laminar to turbulent, important for system design.