Viscometer using drag force measurements

Area of Science:

• Fluid Mechanics
• Rheology
• Instrument Development

Background:

• Accurate viscosity measurements are crucial for understanding fluid behavior.
• Existing viscometers often require larger sample volumes, limiting their application.
• Developing precise instruments for small fluid volumes is an ongoing challenge.

Purpose of the Study:

• To present a robust and precise viscometer design.
• To demonstrate the device's capability with small fluid volumes (0.031 ml).
• To validate the viscometer's performance with Newtonian and non-Newtonian fluids.

Main Methods:

• Utilizing forces exerted by laminar flow within a small duct.
• Measuring force on a long cylindrical sensor immersed in the fluid.
• Testing two devices with volumes of 1.4 ml and 0.031 ml.
• Operating at shear rates from 0.3 to 2550 s⁻¹.

Main Results:

• Verified linear response for Newtonian fluids (viscosity 10⁻³ to 0.1 Pa·s).
• Achieved 90% agreement with commercial rheometers for Newtonian fluids.
• Successfully determined shear rate-dependent viscosity for non-Newtonian polymer solutions.
• Identified power-law behavior and rheological parameters for shear-thinning polymer solutions.

Conclusions:

• The developed viscometer is robust, precise, and effective for small fluid volumes.
• The technique accurately measures viscosity across a wide range of shear rates.
• The instrument is suitable for characterizing both simple and complex fluid rheology.