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Collagen is known to play a key role in the fracture resistance of bone. Here, in situ synchrotron tomography during the mechanical testing of bone is combined with deep learning to mitigate radiation damage, revealing that a compromised collagen network lowers the efficacy of crack deflection.

In this study, vorticity dissipation phenomenon within a curved shear layer while Karman vortices are formed behind a body was investigated experimentally based on time variation of energy dissipation function distribution. The vorticity dissipation within a separated shear layer would be caused by viscous effect associated with shear strain in the process of pairing between two vortices formed by Kelvin-Helmholtz instability. Therefore, in this experiment, the vortex pairing phenomenon within a separated shear layer was reproduced within a centrifugally stable curved free shear layer. Time variation of velocity distribution in one period of vortex pairing process was obtained by means of L.D.V. and phase ensemble averaging technique. By differentiating the velocity distribution for each phase of pairing process, time varying distributions of vorticity, shear strain rate and energy dissipation function were obtained and investigated. As the results, it was found that the strong shear strain occurs and energy is dissipated significantly when the vortices are started to starch in the process of pairing. Also, it was found that the diffusion of vorticity from the vortices to surrounding irrotational fluid becomes significant after the vortices are fully stretched, instead of in the process of stretching. Moreover, it was found that the energy dissipation by shear strain is almost ended when the pairing vortices align vertically, that is defined as the "merging location."

In this experimental study, fluid dynamic response characteristics of wake galloping between two square prisms of same size in tandem and staggered arrangement to their relative position and free stream velocity were investigated. An immovable square prism of size d was fixed at upstream side and another vibratile square prism was placed at downstream side. The relative position of the vibratile downstream prism to the upstream prism was varied in the range from 1.6 d to 3.1 d in stream-wise direction, and in the range from 0.0 d to 2.1 d in cross flow direction. The vibratile prism at downstream side is elastically supported at it's both end and is ristricted to vibrate in only cross-flow direction. Instantaneous displacement of vibratile prism was measured by means of Laser Displacement Anemometer, and degree of vibration was evaluated by rms value of the fluctuating displacement. At first, response characteristics of wake galloping to relative position and flow velocity were investigated by free-vibration experiments in tandem and staggered arrangements using a wind tunnel. From the experiments, it was found that the response characteristics can be classified into three patterns in relation to relative positions and free stream velocities. Then the wake galloping phenomena occurred in the free-vibration experiments were reproduced by forced-vibration experiments in a water channel to conduct flow visualization. The visualization results well explained the phenomena observed in the wind tunnel experiment.