Viscosity measurement of Newtonian liquids using the complex reflection coefficient
Ediguer E Franco1, Julio C Adamowski, Ricardo T Higuti
1Escola Politecnica da Universidade de Sao Paulo, Sao Paulo, Brazil. ediguer.franco@poli.usp.br
Summary
This study introduces an ultrasonic shear reflectance method for measuring liquid viscosity. The technique accurately determines viscosity for Newtonian liquids and reveals non-Newtonian behavior in more viscous oils.
Area of Science:
- Materials Science
- Physical Chemistry
- Acoustics
Background:
- Accurate viscosity measurement is crucial for characterizing fluid properties.
- Traditional methods may struggle with non-Newtonian fluids or require large sample volumes.
- Ultrasonic techniques offer a non-invasive approach to fluid characterization.
Purpose of the Study:
- To implement and validate an ultrasonic shear reflectance method for viscosity measurement.
- To investigate the viscosity of Newtonian and non-Newtonian liquids using this ultrasonic technique.
- To compare ultrasonic viscosity measurements with a conventional rotational viscometer.
Main Methods:
- Utilized ultrasonic shear reflectance involving mode conversion between longitudinal and shear waves.
- Employed a measurement cell with an ultrasonic transducer, buffers, prism, and sample chamber.
- Measured the complex reflection coefficient (magnitude and phase) at a solid-liquid interface.
Main Results:
- Viscosity measurements for olive oil and automotive oils (SAE 40, 90, 250) were performed at various temperatures and frequencies.
- Ultrasonic results for less viscous liquids agreed with rotational viscometer data, confirming Newtonian behavior.
- More viscous liquids exhibited significant deviations, indicating non-Newtonian behavior not described by the Kelvin-Voigt model.
Conclusions:
- The ultrasonic shear reflectance method is effective for viscosity measurement of Newtonian liquids.
- The technique successfully identified non-Newtonian behavior in higher viscosity oils.
- Further model development is needed to accurately describe the observed non-Newtonian fluid dynamics.
Related Concept Videos
01:27Viscosity
Viscosity is a property of fluids that measures their resistance to flow. It is influenced by factors such as the surface area of contact, the gradient of flow speed, and the fluid's viscosity constant, called the coefficient of viscosity. The coefficient of viscosity, also known as dynamic viscosity, is denoted by the symbol η. It determines the proportionality between the viscous force and the gradient of flow speed.Newton's law of viscosity states that the viscous force on a faster-moving...
01:17Viscosity
When water is poured into a glass, it falls freely and quickly, whereas if honey or maple syrup is poured over a pancake, it flows slowly and sticks to the surface of the container. This difference in the flow of different kinds of liquids arises due to the fluid friction between the liquid layers and the liquid and the surrounding material. This property of fluids is called fluid viscosity. In this example, water has a lower viscosity than honey and maple syrup.
The SI unit of viscosity is...
The SI unit of viscosity is...
01:19Viscosity of Fluid
Viscosity measures the resistance a fluid offers to flow and deformation. It results from internal friction between layers of fluid moving relative to one another. Dynamic viscosity, denoted by the Greek letter mu (μ), quantifies the force needed to move one fluid layer over another. For Newtonian fluids like water and air, the relationship between the shearing stress and the rate of shearing strain is linear, meaning their viscosity remains constant regardless of the applied stress.
01:18Newtonian Fluid: Problem Solving
Newtonian fluids exhibit a constant viscosity, meaning their shear stress and shear strain rate are directly proportional. This property ensures a predictable and stable response to applied forces, maintaining a linear relationship between force and flow. Examples include water, air, and light oils, consistently demonstrating this proportional behavior regardless of external conditions.
A velocity gradient forms within the fluid when a Newtonian fluid is placed between two parallel plates, with...
A velocity gradient forms within the fluid when a Newtonian fluid is placed between two parallel plates, with...
02:57Surface Tension, Capillary Action, and Viscosity
Surface Tension
The various IMFs between identical molecules of a substance are examples of cohesive forces. The molecules within a liquid are surrounded by other molecules and are attracted equally in all directions by the cohesive forces within the liquid. However, the molecules on the surface of a liquid are attracted only by about one-half as many molecules. Because of the unbalanced molecular attractions on the surface molecules, liquids contract to form a shape that minimizes the number...
The various IMFs between identical molecules of a substance are examples of cohesive forces. The molecules within a liquid are surrounded by other molecules and are attracted equally in all directions by the cohesive forces within the liquid. However, the molecules on the surface of a liquid are attracted only by about one-half as many molecules. Because of the unbalanced molecular attractions on the surface molecules, liquids contract to form a shape that minimizes the number...
01:10Poiseuille's Law and Reynolds Number
Any fluid in a horizontal tube can flow due to pressure differences—fluid flows from high to low pressure. The flow rate (Q) is the ratio of pressure difference and resistance through a horizontal tube. The greater the pressure difference, the higher the flow rate. The flow resistance is expressed as: