{"id":571,"date":"2022-10-08T10:14:33","date_gmt":"2022-10-08T01:14:33","guid":{"rendered":"https:\/\/lfc.media-creations.org\/?page_id=571"},"modified":"2022-12-07T15:08:40","modified_gmt":"2022-12-07T06:08:40","slug":"doc6-page-en","status":"publish","type":"page","link":"https:\/\/c-mng.cwh.hokudai.ac.jp\/lfc-me.eng\/Root\/research-project-en\/project-en\/doc6-page-en.html","title":{"rendered":"Development and application of USR"},"content":{"rendered":"\n
\u201cRheology is science of material deformation without considering fluid flows.\u201d Some researchers have explained so. This is because torque rheometer, which is the standard tool to evaluate rheological properties of fluids, assumes ideal shear conditions in a test fluid layer. To keep the conditions the layer is required to be thin enough, around 1 mm, but there are multiple factors that make the conditions to be unsatisfied in testing general materials, for example, slip on the sensing walls, shear banding, elastic instability, and heterogeneity of test materials.<\/p>\n\n\n\n
\u3000We, LFC researchers and students, have investigated bubble suspension rheology in the framework of studies on bubbly drag reduction, and noticed that there is no suitable tool to explore the bubble rheology. Idea of ultrasonic spinning rheometry (USR) was thus invented along our research philosophy. Velocity-profiling-assisted rheometer had been temporarily introduced to solve the problem of imperfect shear conditions in the torque rheometer, but USR completely stands apart from these methods.
Principle:<\/strong> USR utilizes an open top cylindrical container filled with a test fluid (see the figure below) in periodic oscillations with a certain frequency and an amplitude. The oscillation of the cylinder wall thus propagates toward interior of the test fluid depending on local rheological properties. Shear rate distributes in the radial direction of the cylinder, and thus time variations of instantaneous radial velocity profiles reflect the rheological properties. If we can assume ideal one-directional, axisymmetric flow in the azimuthal direction, for the fluid flow in the cylinder, the flow is dominated by Cauchy\u2019s equation of motion,<\/p>\n\n\n\n