1. What is Critical Velocity of Fluid?

Definition: Critical velocity is the maximum velocity at which fluid flow transitions from laminar to turbulent flow.

Purpose: This calculation helps engineers and scientists determine flow characteristics in pipes, channels, and other fluid systems.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( V_c \) — Critical velocity (m/s)
• \( Re \) — Reynolds number (unitless)
• \( \eta \) — Dynamic viscosity (Pa·s)
• \( \rho \) — Fluid density (kg/m³)
• \( D \) — Characteristic diameter (m)

Explanation: The formula relates the dimensionless Reynolds number to the actual critical velocity using fluid properties and system dimensions.

3. Importance of Critical Velocity Calculation

Details: Knowing the critical velocity helps in designing efficient fluid transport systems, predicting flow behavior, and preventing unwanted turbulence.

4. Using the Calculator

Tips: Enter the Reynolds number, fluid viscosity, fluid density, and characteristic diameter. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical Reynolds number for transition?
A: For circular pipes, transition typically occurs around Re = 2300, but this can vary based on surface roughness and other factors.

Q2: How do I determine viscosity?
A: Viscosity can be measured experimentally or found in fluid property tables for common substances.

Q3: What is characteristic diameter?
A: For pipes, it's the inner diameter. For non-circular channels, use the hydraulic diameter (4 × area/perimeter).

Q4: Does this work for all fluids?
A: Yes, the formula applies to Newtonian fluids. Non-Newtonian fluids require more complex calculations.

Q5: Why is critical velocity important?
A: It helps determine when flow becomes turbulent, which affects pressure drop, mixing efficiency, and energy requirements.