Acoustic Waveguide for Liquid Viscosity and Temperature Measurement
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Solution Overview
Problem
Current methods for measuring physical and chemical characteristics of liquids and soft materials, such as highly viscous or paste-like mediums, face limitations in accurately determining properties like viscosity and temperature gradients due to the reciprocity of energy coupling between the acoustic waveguide and the medium, which affects the propagation of surface and volume sound waves.
Innovation Solution
The use of an acoustic waveguide with a thickness that allows concurrent propagation of Lamb or transition-type surface acoustic waves on both inner and outer surfaces, enabling efficient energy conversion between surface and volume sound waves, and the application of piezoelectric or non-piezoelectric materials with interdigital electrodes or wedge-shaped transducers to excite and receive these waves, allowing for precise measurement of properties like viscosity and temperature gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the waveguide is dipped into the medium or the medium is filled into the interior space of the waveguide, then the characteristics of the medium can be determined through acoustic wave coupling, but the energy coupling between the waveguide and medium affects the propagation of surface and volume sound waves, limiting measurement accuracy
Solution Approach 1:
The patent changes the physical parameters of the waveguide by using a thin-walled structure where the wall thickness is smaller than the penetration depth of the surface acoustic waves. This parameter change allows the waves to propagate through both the inner and outer surfaces simultaneously, creating correlated wave patterns that enable accurate determination of medium characteristics while minimizing energy loss through controlled coupling.
Solution Approach 2:
The patent replaces traditional bulk acoustic wave measurement methods with surface acoustic wave-based measurement. By using Rayleigh waves and Lamb waves that propagate along the surface of the thin-walled waveguide, the system achieves more sensitive detection of medium properties while reducing the harmful effects of energy coupling that plague conventional mechanical acoustic measurement systems.
2Use of energy by moving object
If surface acoustic waves are generated in the waveguide, then energy can be coupled into the medium for measurement, but the velocity mismatch between surface and volume sound waves limits the efficiency of energy coupling
Solution Approach 1:
The patent addresses the velocity mismatch by changing the geometric parameters of the waveguide, specifically using a thin-walled structure. This configuration allows surface acoustic waves with velocity cS to efficiently couple energy into volume sound waves with velocity cM in the medium, overcoming the velocity mismatch limitation and enabling effective energy transfer for measurement purposes.
3Measurement precision
If the waveguide wall thickness is reduced to enable surface acoustic wave propagation on both surfaces, then measurement sensitivity increases, but the structural strength of the waveguide decreases
Solution Approach 1:
The patent employs a thin-walled waveguide structure where the wall thickness is deliberately reduced to be smaller than the penetration depth of surface acoustic waves. This thin-walled design enables the waves to propagate through both the inner and outer surfaces, creating the correlated wave patterns necessary for sensitive measurements while maintaining sufficient structural integrity through appropriate material selection and design.
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 approach enables accurate determination of physical and chemical properties, including viscosity and temperature gradients, by measuring propagation delays and amplitudes of wave pulses along different paths, effectively overcoming previous limitations in energy coupling and wave propagation.
Implementation Method 1
If the external walls of the acoustic waveguide are made of a piezoelectric material, then metallic electrodes, such as interdigital electrodes, may be used as a transducer (sender) to excite surface acoustic waves upon application of an alternating voltage/alternating current.
Implementation Method 2
concurrent surface acoustic waves are propagating on both the inner and outer surface of a waveguide (accompanied by a concurrent displacement of surface atomic layers on both surfaces)
Implementation Method 3
If the external walls of the acoustic waveguide are made of a piezoelectric material, then metallic electrodes, such as interdigital electrodes, may be used as a transducer (sender) to excite surface acoustic waves upon application of an alternating voltage/alternating current.
Data Source
Figure 1~2
Figure 3A~3C
Figure 4A~4B
AI summary
The invention relates to a method and a device for determining characteristics of a medium in form of a liquid or a soft material, the method comprising the following steps: a) providing an acoustic waveguide defining an inner surface (11, 21) and an outer surface (12, 22) and delimiting an interior space (5) to be filled with the medium (L, L1, L2, LE) to be measured such that the inner surface (11, 21) of the waveguide forms an interface with the medium, b) providing a sender (3) for feeding acoustic wave energy into the waveguide, c) providing a receiver (4) for receiving surface acoustic waves propagating along the waveguide, d) exciting surface acoustic waves in the waveguide by means of the sender (3), e) converting at least a part of the energy associated with the surface acoustic waves (S1) into volume sound waves (S3) of the medium (L, L1, L2, LE), f) propagating both surface acoustic waves (S1, S2) and volume sound waves (S3) along a direction of extension (E) of the waveguide, g) reconverting at least a part of the energy associated with the volume sound waves (S3) into acoustic wave energy of the waveguide thereby generating surface acoustic waves (S1, S2), h) determining characteristics of the medium (L, L1, L2, LE) from a signal generated by the receiver (4) upon receipt of surface acoustic waves (S2); wherein a thickness (d) of the acoustic waveguide, defined as a distance between the inner surface (11, 21) and the outer surface (12, 22) of the acoustic waveguide, is such that concurrent surface acoustic waves are propagating on both the inner and the outer surface (11, 21; 12, 22) of the acoustic waveguide.