What Is the Capillary Number (Ca) Microfluidic Flow Calculator?
The Capillary number represents the relative importance of viscous forces versus surface tension forces acting across an interface between two immiscible fluids.
How Does the Capillary Number (Ca) Microfluidic Flow Calculator Work?
Multiplies dynamic viscosity by characteristic flow velocity.
Divides by interfacial tension σ.
Classifies the governing flow regime.
Capillary Number (Ca) Microfluidic Flow Calculator Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
Ca = (µ · v) / σ
Ratio of viscous hydrodynamic shear forces to interfacial capillary forces.
How to Use the Capillary Number (Ca) Microfluidic Flow Calculator
- Enter fluid viscosity in Pa·s.
- Enter velocity in m/s and surface tension in N/m.
Step-by-Step Example Calculation
Water Droplet Microchannel Flow
Input Values:
viscosity:0.001
velocity:0.1
surfaceTension:0.05
Worked Steps: Water flowing at 0.1 m/s with 0.05 N/m interfacial tension yielding Ca = 0.002.
Understanding Your Result
Ca << 1: Capillary forces dominate; droplets remain spherical.
Ca > 1: Viscous forces dominate; droplets stretch into filaments and break up.
Factors That Affect the Result
- Surfactant concentration (reduces σ, increasing Ca).
When Should You Use This Calculator?
- Droplet-based microfluidics, enhanced oil recovery (EOR), and coating flows.
Assumptions & Limitations
- Assumes laminar flow (low Reynolds number).
Frequently Asked Questions
Calculation Accuracy & Reference Note
Standard dimensionless fluid dynamics group.