Double Wall Rheometer Apertures Reduce Surface Tension
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Solution Overview
Problem
Rotational rheometers face challenges in accurately measuring rheological properties due to surface tension effects at the free liquid interface and fluid pumping issues, which introduce errors in force measurements during orthogonal superposition tests.
Innovation Solution
The implementation of a double wall orthogonal superposition rotational rheometer with apertures in the cylindrical bob to minimize surface tension effects and openings in the inner wall of the double wall cup to reduce fluid pumping, allowing for simultaneous application of rotational and axial shear flows, thereby improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a traditional single-wall cup design is used, then the device structure is simple, but surface tension effects at the free liquid interface cause measurement errors
Solution Approach 1:
The cup is divided into an inner wall and an outer wall, forming a double-wall structure. The inner wall contains openings that segment the fluid path, allowing fluid to be drawn into the central chamber and reducing the free liquid interface area, thereby minimizing surface tension effects while maintaining structural integrity
Solution Approach 2:
The inner wall is nested within the outer wall, creating a concentric double-wall configuration. The openings in the inner wall allow fluid communication between the annular chamber and central chamber, enabling the nested structure to simultaneously reduce surface tension effects and maintain device simplicity
2Measurement precision
If the bob moves downwards during testing, then axial displacement measurement is achieved, but fluid pumping effects introduce errors in force measurements
Solution Approach 1:
The harmful fluid pumping effect is extracted and redirected by the openings in the inner wall. When the bob moves downward, fluid is drawn through the openings into the central chamber, removing the pumping effect from the measurement path and converting it into a controlled fluid flow that does not interfere with force measurements
Solution Approach 2:
The openings in the inner wall act as an intermediary mechanism between the annular chamber and central chamber. They mediate the fluid flow during bob displacement, allowing controlled fluid movement that eliminates harmful pumping effects while maintaining proper fluid communication
3Measurement precision
If apertures are added to the bob to reduce surface tension effects, then measurement accuracy improves, but the device complexity increases
Solution Approach 1:
Apertures are added only to specific locations on the bob (top and bottom surfaces), not throughout the entire structure. This localized modification reduces surface tension effects at critical interfaces while maintaining the overall simplicity of the bob design and minimizing additional complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances measurement accuracy by reducing surface tension effects and fluid pumping errors, resulting in improved precision for both higher and lower viscosity materials, with improvements ranging from 10% to 50% compared to prior art test modules.
Implementation Method 1
Surface tension effects at the top of the rheometer's double wall cup are minimized by apertures in the top portion of the bob that reduce effects of the free liquid interface in the gap on the force measurement
Implementation Method 2
Fluid pumping effects at the bottom of the rheometer's double wall cup are minimized by openings in the inner wall of the double wall cup that allow fluid to be displaced when the bob moves downwards
Data Source
Figure 1
Figure 2
Figure 3a~3d
AI summary
An orthogonal superposition rotational rheometer that applies a rotational torque and an orthogonal axial oscillatory stress to a fluid. The rheometer uses a cylindrical bob in a double wall cup to apply shear rotational and axial forces to the fluid. Openings in the top section of the cylindrical bob reduce surface tension effects on the force measurement. Fluid pumping effects at the bottom of the rheometer's double wall cup are minimized by openings in the inner wall of the double wall cup that allow fluid to be displaced when the bob moves downwards.