Classify internal pipe flow using a specified water-like liquid property set. Density and viscosity are fixed example inputs, not a claim that both describe water at one exact temperature.
1. Calculator Inputs
Select the units below before entering the numbers. These are fixed benchmark inputs for checking the calculator.
| Calculator field | Value | Unit / setting |
|---|---|---|
| Viscosity input | Dynamic viscosity + density | |
| Velocity | 6 | ft/s |
| Characteristic diameter | 2.067 | in |
| Density | 62.4 | lbm/ft³ |
| Dynamic viscosity | 1 | cP |
2. Step-by-step Math
Convert all quantities to consistent units
V = 6 × 0.3048 = 1.8288 m/s D = 2.067 × 0.0254 ≈ 0.0525 m ρ = 62.4 × 0.45359237 / 0.3048³ = 999.5521145 kg/m³ μ = 1 cP ≈ 0.001 Pa·s
Using SI for the intermediate calculation avoids mixing lbm-based viscosity with SI density. No gravitational conversion factor belongs in this Reynolds-number equation.
Calculate Reynolds number
Re = ρVD / μ Re = 999.5521145 × 1.8288 × 0.0525018 / 0.001 Re ≈ 96,000
The units cancel. The calculator classifies this result as turbulent because it exceeds 4,000.
Cross-check with kinematic viscosity
ν = μ / ρ = 0.000001000448086 m²/s ν ≈ 1 cSt Re = VD / ν ≈ 96,000
Switch Viscosity input to Kinematic viscosity and enter 1.000448086 cSt, keeping the same velocity and diameter. The Reynolds number should agree within display rounding.
3. Compare Your Answers
Keep full precision during the calculation. The calculator may display fewer digits; compare answers rounded to three significant figures; retain unrounded intermediate values.
| Result | Expected answer | Your answer |
|---|---|---|
| Reynolds number | 96,000 (approximately) | __________ |
| Flow regime | Turbulent | __________ |
| Equivalent kinematic viscosity | 1 cSt | __________ |
Second check
For a laminar check, return to Dynamic viscosity + density and change viscosity to 100 cP. Reynolds number falls by a factor of 100 to 960, and the regime becomes Laminar.
4. Assumptions and Method
The classification applies to conventional internal pipe flow: laminar at Re ≤ 2,300, transition between 2,300 and 4,000, and turbulent at Re ≥ 4,000. These are practical boundaries. Non-Newtonian fluids may need a different definition.
Equation definitions and implementation: Reynolds Number Calculator. See also calculation methodology and other worked examples.