Turbulent Flow Calculator

Reynolds Number Equation:

\[ Re = \frac{\rho \cdot v \cdot D}{\mu} \]

Density (ρ):

kg/m³

Velocity (v):

m/s

Diameter (D):

Viscosity (μ):

Pa·s

Reynolds Number (Re):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is Reynolds Number?

The Reynolds number (Re) is a dimensionless quantity used to predict flow patterns in fluid dynamics. It represents the ratio of inertial forces to viscous forces and determines whether flow will be laminar, transitional, or turbulent.

2. How Does the Calculator Work?

The calculator uses the Reynolds number equation:

\[ Re = \frac{\rho \cdot v \cdot D}{\mu} \]

Where:

\( Re \) — Reynolds number (unitless)
\( \rho \) — Fluid density (kg/m³)
\( v \) — Flow velocity (m/s)
\( D \) — Characteristic diameter (m)
\( \mu \) — Dynamic viscosity (Pa·s)

Flow Classification:

Re < 2000: Laminar flow (smooth, orderly)
2000 ≤ Re ≤ 4000: Transitional flow
Re > 4000: Turbulent flow (chaotic, mixing)

3. Importance of Reynolds Number

Details: Reynolds number is crucial for predicting friction losses, heat transfer rates, and flow behavior in pipes, channels, and around objects. It's fundamental in engineering applications from water supply systems to aerospace design.

4. Using the Calculator

Tips: Enter all values in SI units. Ensure density and viscosity are positive values. The calculator automatically determines flow regime based on standard Reynolds number thresholds.

5. Frequently Asked Questions (FAQ)

Q1: Why is Reynolds number dimensionless?
A: The units in the numerator (kg/m³ × m/s × m) cancel with the denominator (kg/m·s), resulting in a unitless quantity.

Q2: What's the characteristic diameter?
A: For pipe flow, it's the inner diameter. For non-circular conduits, use hydraulic diameter (4×cross-sectional area/wetted perimeter).

Q3: Can Reynolds number be negative?
A: No, since all parameters (density, velocity, diameter, viscosity) are positive physical quantities.

Q4: How does temperature affect Reynolds number?
A: Temperature affects viscosity significantly. Higher temperature usually decreases viscosity for liquids, increasing Re for the same flow conditions.

Q5: Is turbulent flow always undesirable?
A: Not necessarily. Turbulent flow enhances mixing and heat transfer but increases friction losses. The optimal flow regime depends on the application.