A new portable field rotational viscometer for high-temperature melts.

Area of Science:

• Geophysics and materials science
• Rheology of geological materials
• High-temperature fluid dynamics

Background:

• Laboratory viscometers characterize melts but are confined to controlled environments.
• Measuring viscosity of large volumes of high-temperature melts in situ (e.g., active lava flows) is challenging.
• Existing methods lack portability and real-time analysis for field conditions.

Purpose of the Study:

• To introduce a novel, portable instrument for measuring the viscosity of high-temperature liquids and suspensions.
• To enable in-situ rheological characterization of materials like lava under natural conditions.
• To facilitate the study of geological melts and industrial high-temperature fluids.

Main Methods:

• A portable viscometer featuring a torque sensor and a motor-driven stainless-steel shear vane.
• Integrated thermocouple for real-time melt temperature measurement.
• Onboard microcomputer for simultaneous recording of torque, rotation rate, and temperature.

Main Results:

• The instrument was calibrated using viscosity standards across a wide range of conditions (10-650 Pa·s, 0.1-27.9 s⁻¹, 30-3870 Pa).
• Successful high-temperature tests were conducted with approximately 25 liters of lava between 1000°C and 1350°C.
• The device demonstrated capability for real-time rheological flow curve characterization as a function of temperature and strain rate.

Conclusions:

• The developed portable field viscometer is suitable for measuring the viscosity of geological melts at relevant temperatures in their natural state.
• The instrument's design allows for easy operation and high mobility, making it ideal for field deployment on volcanoes.
• Potential applications extend to industrial settings requiring high-temperature fluid viscosity measurements.