Droplet Breakup and Weber Number: Compare Inertia with Surface Tension

Define the Process Model

The Weber number compares inertia with interfacial tension using We = ρv²L/σ. COMSOL’s dimensionless-number reference defines that relation. In a droplet application, the chosen velocity difference and characteristic size must describe the relevant local interaction. A bulk vessel speed cannot silently replace an across-droplet velocity scale.

Compare a Hypothetical Case

For an invented scale comparison, take ρ = 1,000 kg/m³, L = 100 µm and σ = 0.030 N/m. A selected local velocity scale of 0.10 m/s gives We ≈ 0.0333. Changing that scale to 0.20 m/s gives 0.133. The fourfold change follows the squared velocity; it does not establish that either droplet must break.

Complete the Engineering Review

Write the exact velocity definition, droplet-size basis and interface composition next to the number. Identify the breakup model, flow conditions and any critical value used. A threshold from one documented model should not be generalized to a different flow or viscosity ratio. Keep the measured size distribution separate from a dimensionless comparison calculated from assumed inputs.

For an emulsion-manufacturing discussion, obtain the actual process and geometry evidence. These figures are not HM droplet sizes or homogenization results. They help expose a mismatched scale before a breakup claim is used in a proposal.

Which inertial-to-interfacial stress scale is relevant to the proposed breakup region?

This blank worksheet is for your own project. It contains no H M machine trial result.

Customer Questions

Related Equipment References

Review the actual offered equipment and application separately from this educational example.

• emulsion-manufacturing discussion

Primary References

These references support the technical principles discussed in this guide. The worked examples and review questions are educational.

• COMSOL’s dimensionless-number reference
• emulsion-manufacturing discussion