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Viscosity

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Related Experiment Video

Updated: Jul 17, 2026

Experimental Measurement of Settling Velocity of Spherical Particles in Unconfined and Confined Surfactant-based Shear Thinning Viscoelastic Fluids

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Published on: January 4, 2014

Linear dependence of surface drag on surface viscosity.

Coralie Alonso¹, Joseph A Zasadzinski

¹Departments of Chemical Engineering and Materials, University of California, Santa Barbara, California 93106-5080, USA.

Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics

|March 5, 2004

Summary

This study quantifies interfacial drag on air-water flows using a magnetic needle method. Results show a linear relationship between drag and surface viscosity for lipid monolayers.

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Area of Science:

Fluid dynamics
Surface science
Rheology

Background:

Interfacial flow is influenced by surface and subphase drag.
Measuring surface viscosity is crucial for understanding interfacial phenomena.
Existing methods for drag separation are limited.

Purpose of the Study:

To develop a method for separating interfacial drag contributions.
To measure the surface viscosity of lipid monolayers.
To establish a relationship between interfacial drag and surface viscosity.

Main Methods:

A magnetic needle was used to apply a constant force to a monolayer-covered air-water interface.
Needle velocity was measured to determine the drag coefficient.
Comparison with channel viscometry data was performed.

Main Results:

Needle velocity reached a terminal velocity dependent on the applied force and drag coefficient.
The drag coefficient was found to be linearly proportional to surface viscosity.
This relationship was validated for dipalmitoylphosphatidylcholine monolayers.

Conclusions:

The magnetic needle method effectively quantifies interfacial drag.
Surface viscosity significantly impacts flow dynamics at air-water interfaces.
This technique provides a new way to measure surface viscosity.