Turbulent Flow Rate & Reynolds Number Calculator
Determine flow regime and calculate volumetric flow rate based on pipe geometry and fluid properties.
Calculation Results
Reynolds Number (Re):
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Flow Regime:
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Volumetric Flow Rate (SI):
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Flow Rate (Metric):
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Flow Rate (US):
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Understanding Turbulent vs. Laminar Flow
In fluid dynamics, the flow of a liquid or gas through a pipe typically behaves in one of two ways: laminar or turbulent. Understanding which regime your system operates in is critical for calculating pressure drops, heat transfer rates, and pump sizing.
The Reynolds Number (Re) is the dimensionless quantity used to predict flow patterns. It represents the ratio of inertial forces to viscous forces within a fluid.
Flow Regimes Defined
- Laminar Flow (Re < 2300): The fluid moves in smooth, parallel layers with no disruption between them. Viscous forces dominate. This is common in high-viscosity fluids (like oil) or low velocities.
- Transitional Flow (2300 ≤ Re ≤ 4000): A mix of laminar and turbulent flow. The flow behavior is unpredictable and can fluctuate between the two states.
- Turbulent Flow (Re > 4000): The fluid undergoes irregular fluctuations and mixing. Inertial forces dominate. This is the most common regime for industrial water systems and HVAC piping.
Formulas Used in This Calculator
This calculator uses two primary equations to determine the system state:
1. Reynolds Number Equation
$$Re = \frac{\rho \cdot v \cdot D}{\mu}$$
Where:
- ρ (rho): Fluid Density (kg/m³)
- v: Fluid Velocity (m/s)
- D: Pipe Internal Diameter (m)
- μ (mu): Dynamic Viscosity (Pa·s or N·s/m²)
2. Volumetric Flow Rate Equation
$$Q = A \cdot v$$
Where:
- Q: Flow Rate (m³/s)
- A: Cross-sectional Area of the pipe (m²), calculated as $$\pi \cdot (D/2)^2$$
- v: Velocity (m/s)
Reference Values for Common Fluids
If you are unsure of the fluid properties, here are standard values at 20°C (68°F):
| Fluid | Density (kg/m³) | Viscosity (Pa·s) |
|---|---|---|
| Water | 998 | 0.0010 |
| Seawater | 1025 | 0.00107 |
| Air (at 1 atm) | 1.204 | 0.000018 |
| Motor Oil (SAE 30) | 917 | 0.29 |
*Note: Viscosity is highly dependent on temperature. Ensure you use the viscosity corresponding to your operating temperature for accurate turbulence calculations.