A viscoelastic characterization method using low-velocity impact is experimentally studied. A steel ball is dropped from a certain height and impacts on an agar gel target with 1-4 m/s velocity. The motion of the impactor ball is captured by a high-speed camera. Instantaneous penetration depth, velocity, and acceleration of the impactor are computed from the high-speed video data. The obtained kinematic data are analyzed in terms of the equation of motion of the impactor. Specifically, we compute the impact viscosity and impact elasticity, assuming a simple impact drag force model. The impact drag force model consists of a linear viscous term, a linear elastic term, and a constant term. From the estimated impact viscosity, we confirm that the Reynolds number is relatively low (less than 10). This low Reynolds number is consistent with the simple linear viscous assumption. From the estimated impact elasticity, we can calculate the speed of sound and the strength of target agar gel. In order to examine the velocity dependence of the elasticity, we also perform very slow (less than 0.1 mm/s) penetration tests using the same agar gel samples. The comparison between impact elasticity and slow penetration elasticity reveals the weak velocity strengthening of agar gel. V C 2013 American Institute of Physics.

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In order to study magnetohydrodynamic behavior in electromagnetic pumps, electromagnetic flow meters, etc. for Liquid Metal Fast Reactors (LMFRs), a large eddy simulation method using an artificial wall boundary condition was developed. In this study, Spalding’s law of the wall and the eddy viscosity for uniform magnetic fields, which was proposed by Shimomura, was applied to Finite Element Method of Generalized Simplified Marker and Cell (GSMAC-FEM). We calculated MHD channel flow in various element sizes on the conditions of Hartmann numbers of 0, 52.5 and 125, whose Reynolds numbers based on the average velocity were all about 29,000. These results showed the average velocity profiles were in good agreement with both the experimental results by Brouillette-Lykoudis and the detail calculation results by Shimomura, although farther calculations were needed to verify the turbulence intensities.