Pressure-wave formation and collapses of cavitation clouds impinging on solid wall in a submerged water jet

A high-speed water jet ejected into water forms a cavitating water jet accompanied with cavitation clouds in a periodic manner. A powerful impulsive force can be caused at the collapse of unsteady cavitation clouds at the same time when the cavitating water jet impinges against a solid wall. It is known that this force can be widely used in an industrial field such as cleaning, cutting, and peening. In the present experiment, cavitation clouds are observed to investigate the details such as impinging, dividing and collapsing behaviors using a constrained-type test section as well as an opentype test section. The constrained-type test section is used to quasitwo dimensionally observe the behavior of cavitation clouds in the near impinging wall region. The present purpose is to investigate about the behavior of cavitating water jet in the near impinging wall region as well as the relation of cavitation cloud collapse with the formation of pressure wave, the propagation of pressure wave and the cavitation impact. In order to estimate the high speed phenomena such as rapid and consecutive collapses of cavitation clouds and pressure wave formation, the frame difference method for cavitating flow is used in the present image analysis for cavitation cloud. The usefulness of the method is experimentally verified for the behavior analysis of high speed liquid flow accompanied with growth and collapse of bubbly cloud. As a result it is experimentally found that 1) the present image analysis method based on the frame difference method makes possible to grasp the motion of pressure wave propagation in cavitation cloud, 2) local cloud collapse causes a pressure wave which propagates toward the surrounding area and as a result causes secondary collapses in a chain-reaction manner, and 3) cavitation clouds on the impinging wall tend to be peripherally located in an annular zone at the final collapsing stage. The existence of the annular cloudy zone can be related to the ring-like cavitation erosion distribution and the chain-reaction-type propagation of cavitation clouds.http://deepblue.lib.umich.edu/bitstream/2027.42/84263/1/CAV2009-final66.pd

Random dynamical systems modeling for brain wave synchrony

A random dynamical systems model is studied\ud to understand coupled dynamics of auditory area and\ud motor area modulated by external force. We measure transfer\ud entropy of coupled oscillators with the presence of noise\ud to explain results of human brain wave experiments

Buckling Strength of Cold-Formed Circular Steel Column Subjected to Axial Load

In this study, the global buckling behavior of a cold-formed circular steel column was discussed with a focus on the effects of its mechanical properties and initial imperfections on the behavior. As the first step, the stress–strain curves of the column under tensile and compressive loads as well as its residual stresses were investigated. Subsequently, a finite element analysis was conducted to clarify if the analysis properly simulated the stub column behavior. The analysis results obtained using measured compressive stress–strain curves and residual stresses agreed well with experimental results. Finally, another finite element analysis was performed on the long column buckling to examine the effects of its mechanical properties and initial imperfections. It was shown that the global buckling strength was affected not only by imperfections such as residual stress and out-of-straightness but also by the anisotropic mechanical properties of the material

Surface Roughness Control Based on Digital Copy Milling Concept to Achieve Autonomous Milling Operation

AbstractIn order to develop an autonomous and intelligent machine tool, a system named Digital Copy Milling (DCM) was developed in our previous studies. The DCM generates tool paths in real time based on the principle of copy milling. In the DCM, the cutting tool is controlled dynamically to follow the surface of CAD model corresponding to the machined shape without any NC program. In this study, surface roughness control of finished surface is performed as an enhanced function of DCM. From rough-cut to semi-finish-cut and finish-cut operations, the DCM selects cutting conditions and generates tool paths dynamically to satisfy instructed surface roughness Ra. The experimental verification was performed successfully