arXiv subjects

Masakazu Muto

Publications and source records attributed to Masakazu Muto.

6 recordsLinked to original sources

arXiv2026

Geometric control of powder jet dynamics and energy dissipation

Applying an impulsive force to a powder layer shaped with a concave surface generates a sharp powder jet. This phenomenon has been proposed as a method for evaluating the flowability of powders from small amount of samples. In this study, we systematically varied the radius of the initial concave shape as a controllable parameter and quantitatively examined the resulting jet dynamics, focusing on ejection velocity and maximum height. Our high-speed observations revealed that increasing the concave radius led to broader jets with significantly reduced velocity and maximum height. These dynamic quantities followed a scaling relation with drop height, while the scaling coefficient decreased with the concave radius, indicating that the surface geometry directly governs the extent of energy dissipation. Furthermore, a minimal mechanical model incorporating the sliding distance and velocity squared type dissipation of the powder flow reproduces the observed linear dependence of the jet height on the concave radius. These findings establish powder jets as a sensitive probe of dissipation in dynamic powder flow and provide a quantitative framework for comparing powder specific interactions such as humidity, particle size and particle shape.

cond-mat.soft↗

arXiv2025

Full-field rheo-optical analysis of wormlike and networked micellar structures under uniaxial extensional flow

The present study proposes a novel full-field extensional rheo-optical technique to investigate the relationship between the rheological properties and internal structural deformation of complex fluids under uniaxial extensional flow. Macroscopic viscoelasticity from rheological measurements and microscopic birefringence from optical measurements are integrated to evaluate the microstructural deformation and orientation of the fluids under extensional stress. The proposed technique integrates a liquid dripping method with a high-speed polarization camera to measure the extensional stress and flow birefringence simultaneously. In the liquid dripping method, temporal evolution images of the liquid filament diameter for fluids dripping from a nozzle are measured to obtain the extensional stress loading on the filament. These images are acquired using the high-speed polarization camera that captures full-field two-dimensional (2D) birefringence with high spatiotemporal resolution. Wormlike and networked micellar solutions of cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal) with varying concentrations of CTAB and NaSal are employed as the measurement targets. Consequently, we successfully visualized temporally developing images of the flow birefringence field of uniaxially extending micellar solutions induced by the orientation of micelles. Furthermore, the proposed technique supports investigating the conditions for establishing the stress-optical rule, which is the linear relationship between stress and birefringence. The stress-optical coefficient, which is a proportionality constant indicating the sensitivity of birefringence to stress, is analyzed from these measurements. The stress-optical coefficient under uniaxial extensional flow, obtained using the proposed technique, is confirmed to be comparable to that under shear flow.

physics.flu-dyn↗

arXiv2024

Examination of flow birefringence induced by the shear components along the optical axis using a parallel-plate-type rheometer

In this study, the concept of rheo-optics is applied that explores the flow birefringence caused by stress components along the optical axis of the camera since it is often overlooked in the traditional theories of photoelastic flow measurement. A novel aspect of this research is that it involved conducting polarization measurements on simple shear flows, specifically from a perspective in which a shear-velocity gradient exists along the camera's optical axis. A parallel-plate-type rheometer and a polarization camera are employed for these systematic measurements. The experimental findings for dilute aqueous cellulose nanocrystal suspensions demonstrates that the flow birefringence can be expressed as a power law based on the power of the second invariant of the deformation-rate tensor. This suggests that flow birefringence can be universally characterized by the coordinate-independent invariants and a pre-factor determined by the direction of polarization measurement. By adjusting the nonlinear term in the stress-optic law, its applicability could be expanded to include three-dimensional fluid stress fields in which the stress is distributed along the camera's optical axis.

cond-mat.soft↗

arXiv2024

Simultaneous measurement of extensional stress and flow birefringence field for uniaxially extending worm-like micellar solutions

The present study proposes a novel and simple rheo-optical technique to investigate the relation between the rheology of complex fluids and their internal structural deformation under uniaxial extensional flow. The macroscale results of viscoelasticity from rheological measurements and microscale results of birefringence from optical measurements are combined to evaluate the microstructural deformation and orientation state inside the fluids under extensional stress. The proposed technique combines a liquid dripping method with a high-speed polarization camera to measure the extensional stress and flow-induced birefringence field simultaneously. In the liquid dripping method, temporal evolution images of the liquid filament diameter for fluids dripping from a nozzle are measured to obtain the extensional stress loading on the liquid filament. These images are captured with a high-speed polarization camera connected to a micro polarization element alley, enabling high-speed imaging of the birefringent field. Worm-like micellar solutions of cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal) with varying concentrations of CTAB and NaSal are employed as the measurement targets. Consequently, we successfully visualized temporally developing images of the birefringence field of uniaxially extending worm-like micellar solutions induced by the orientation of micelles toward the extensional direction. Furthermore, the proposed technique supports investigating the conditions for establishing the stress-optical rule, which is the linear relation between stress and birefringence for complex fluids. The stress-optical coefficient, a proportionality constant indicating the sensitivity of birefringence to stress, is analyzed from these measurements. The stress-optical coefficient under uniaxial extensional flow is confirmed to be comparable to that under shear flow.

physics.flu-dyn↗

arXiv2024

Flow birefringence of cellulose nanocrystal suspensions in three-dimensional flow fields: revisiting the stress-optic law

This study systematically investigates the flow birefringence of cellulose nanocrystal (CNC) suspensions. The aim is to clarify the importance of the stress component along the camera's optical axis in the stress-optic law (SOL), which describes the relationship between birefringence, the retardation of transmitted polarized light, and the stress field. More than 100 datasets pertaining to the retardation of CNC suspensions (concentrations of 0.1, 0.3, 0.5, and 1.0 wt\%) in a laminar flow field within a rectangular channel (aspect ratios of 0.1, 1, and 3) are systematically obtained. The measured retardation data are compared with the predictions given by the conventional SOL excluding the stress component along the camera's optical axis and by the SOL including these components as second-order terms (2nd-order SOL). The results show that the 2nd-order SOL gives a significantly better agreement with the measurements. Based on the 2nd-order SOL, the retardation at the center of the channel, where the effect of the stress component along the camera's optical axis is most pronounced, is predicted to be proportional to the square of the flow rate, which agrees with the experimental data. The results confirm the importance of considering the stress component along the camera's optical axis in the flow birefringence of CNC suspensions at high flow rates, even for quasi-two-dimensional channel flow.

physics.flu-dyn↗

arXiv2023

Measurement of flow birefringence induced by the shear components along the optical axis using a parallel-plate-type rheometer

The present study investigated the flow birefringence induced by shear components along a camera's optical axis, which has been neglected in conventional theories of photoelastic measurements. Measurements were conducted for a wide range of shear rates from a direction perpendicular to the shear using a high-speed polarization camera and a parallel-plate-type rheometer. The measurement results obtained from a fluid with low viscoelasticity, specifically a dilute suspension of cellulose nanocrystals, showed that the birefringence increases monotonically as the stress components along the camera's optical axis increase. It was also found that the birefringence showed a power law with respect to the shear rate. This letter reports a key fact required for polarization measurements of shear rate (shear stress) in three-dimensional flows.

physics.flu-dyn↗