This study investigated the influence of the rheological and tribological parameters of a food bolus on the organ surface during swallowing. A swallowing simulator was developed based on a three-dimensional moving-particle simulation with a realistic human organ model. The simulator enables numerical comparisons using a standard human model based on food models with different rheological and tribological parameters. Through a parametric study, we can successfully characterize several aspiration patterns for low viscosity with high-density and high-viscosity food models. Our results revealed that the main cause of the before aspiration was the fast bolus arrival at the epiglottis and not the small particles. The results also revealed that to control the outbreak of the spray for aspiration restraints, it is important to control the lubrication of the bolus. This study is not a simple aspiration simulation. Moreover, it can contribute to building an evaluation system that connects the properties of a food bolus with the aspiration phenomenon without any medical radiation risks. Based on the results, we conclude that our swallowing simulator is a useful tool for estimating and evaluating the aspiration phenomena, including the relationship between human organ movement and rheological and tribological properties of the food and organ surface.

To utilize a super-hydrophobic tetradecane-adsorbed marshmallow-like gel as a phase-change material (PCM) as a carrier for latent heat transportation by mixing the gel particles with sodium carboxymethyl cellulose (CMC) solution, the dispersion characteristics and flow characteristics of a marshmallow-like gel slurry were investigated. To investigate the dispersion characteristics of the slurry, visual observation of the slurry under static conditions was performed while varying the concentration of CMC, and the apparent dispersion fraction was determined for quantifying dispersion characteristics. The apparent dispersion fraction stabilized within 2 h. At CMC concentrations of < 0.4, 0.6–2, and > 3 wt%, the apparent dispersion fraction increased, remained constant, and reached the complete dispersion state, respectively. At several concentrations, the viscosity of the liquid layer of the gel slurries was lower than that of the pure solution, coinciding with the range where the apparent dispersion fraction increased. Therefore, it was found that the adsorption of CMC onto the surface of marshmallow-like gel affects the dispersion characteristics of marshmallow-like gel slurry. To investigate flow characteristics, friction factor of CMC solution and marshmallow-like gel slurry against Reynolds number was measured. From the results, it was confirmed that the shear-thinning of the CMC solution affected the flow characteristics.

Flows of nanofluids with rod-like nanoparticles in a microscale channel having cylindrical micro pin heat sinks were numerically simulated to analyze the effect of the aspect ratio of the rod-like particles on the heat transfer and flow in the microscale channel. Furthermore, the optimal aspect ratio was investigated by examining the trade-off relationship between the pressure drop and the thermal efficiency. The Hamilton-Crosser model and Brenner’s model were used to describe the thermal conductivity and viscosity of nanofluids, respectively. The numerical simulations revealed that heat flux around the cylinders was more active in the upstream region and increased with increasing the inlet particle volume fraction ϕ_in and the particle aspect ratio s and that the effect of the aspect ratio tended to decrease gradually. Furthermore, it was found that the thermal efficiency improved with increasing ϕ_in and s but saturated above ϕ_in = 0.04 and s = 30, whereas the pressure drop increased further and the increase was more pronounced at large aspect ratios. These results imply that nanofluids with relatively low particle concentration and small particle aspect ratio are suitable as working fluids for heat exchangers.