1. What is Stokes Law?

Stokes Law describes the settling velocity of small spherical particles in a fluid medium. It's fundamental in fields like sedimentology, wastewater treatment, and aerosol science.

2. How Does the Calculator Work?

The calculator uses the Stokes Law equation:

Where:

• \( v \) — Settling velocity (m/s)
• \( \rho_p \) — Particle density (kg/m³)
• \( \rho_f \) — Fluid density (kg/m³)
• \( \mu \) — Dynamic viscosity (Pa·s)
• \( g \) — Gravitational acceleration (9.81 m/s²)
• \( r \) — Particle radius (m)

Explanation: The equation shows that settling velocity increases with particle size and density difference, but decreases with higher viscosity.

3. Importance of Settling Velocity

Details: Settling velocity calculations are crucial for designing sedimentation tanks, understanding particle behavior in fluids, and analyzing airborne particulate matter.

4. Using the Calculator

Tips: Enter all values in SI units. Ensure particle radius is in meters (not micrometers). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What are the assumptions of Stokes Law?
A: Spherical particles, laminar flow (Re < 1), smooth surfaces, no particle-particle interactions, and constant temperature.

Q2: When is Stokes Law not applicable?
A: For non-spherical particles, turbulent flow, very small particles (where Brownian motion dominates), or concentrated suspensions.

Q3: What's the typical range of settling velocities?
A: From micrometers per second for clay particles to centimeters per second for sand grains in water.

Q4: How does temperature affect settling velocity?
A: Higher temperature reduces viscosity (increasing velocity for liquids) but may also affect density differences.

Q5: Can this be used for air particles?
A: Yes, but only for particles large enough that Brownian motion is negligible (typically >1μm).