Experimental study of perturbations modeled by a membrane in 2D and 3D boundary layers

The work is devoted to experimental studies of the dynamics of the development of perturbations introduced by a membrane under various conditions. The studies were carried out under conditions of a low and moderate degree of free-flow turbulence. It is shown that the impulsive motion of the membrane generates a localized longitudinal structure in the boundary layer, as well as wave packets at its fronts. A circular membrane generates wave packets consisting of forward and oblique waves, while a rectangular membrane generates predominantly forward waves. A moderate degree of turbulence inhibits the development of wave packets at the linear stage and intensifies at the nonlinear stage. The separation of the boundary layer stimulates an increase in the amplitude of the wave packets.

Impulsive Motion in a Cylindrical Fluid-Filled Tube Terminated by a Converging Section

The syringe in a subcutaneous auto-injector may be subjected to internal pressure transients due to the normal operation of the injection mechanism. These transients are similar to transients in fluid-filled pipelines observed during water hammer events. In this paper, the effect of an air gap in the syringe and a converging section is studied experimentally and numerically in a model system which consists of a fluid-filled metal tube that is impulsively loaded with a projectile to simulate the action of the auto-injector mechanism operation. The air between the buffer and the water results in a complex interaction between the projectile and the buffer. Also, there are tension waves inside the tube due to the presence of a free surface and the motion of the buffer, and this causes distributed cavitation which, in turn, gives rise to steepening of the pressure waves. The converging section can amplify the pressure waves if the wave front is sharp, and it can enhance the collapse of bubbles. Pressures as high as 50 MPa have been measured at the apex of the cone with impact velocities of 5.5 m/s.

Earthquake Damages and Disaster Prevention of Aboveground Storage Tanks

Severe damages in aboveground storage tanks (AST) have been often experienced due to earthquakes in Japan. In this paper, earthquake damages of ASTs which occurred for the last several decades are reviewed. These are damages in the 1964 Niigata Earthquake, the 1978 Miyagi Earthquake, the 1983 Sea of Japan Earthquake, the 1995 Kobe Earthquake, the 2003 Hokkaido Earthquake and the 2011 Great East Japan Earthquake. The damages of ASTs can be classified into 3 types in accordance with the characteristics of earthquake. These are the impulsive motion due to a high frequency earthquake, the sloshing motion due to a low frequency earthquake and the tsunami attack. In the impulsive motion, buckling of sidewall plates and uplift of sidewall-to-bottom joints occurred. In the sloshing motion, sinking of floating roofs into liquid and buckling of sidewall-to-roof joints occurred. In the tsunami attack, ASTs moved and overturned to leak oil.

Differential Casimir measurements on an engineered sample: Some experimental details

An experimental technique has been recently developed to measure forces differentially between two samples with similar but not identical compositions. The implementation of this approach, with the important reduction in common background effects is reported. An Au-covered rotating sample composed of Au and Ni sectors interacts with either Au-or Ni- covered spheres. Emphasis is paid to the discussion of remnant systematic effects and their impact on the measurements. It is observed that a residual impulsive motion of the axis of rotation of the apparatus remain, contributing at the 0.1 fN level. Apparently random oscillations of the axis of rotation also increase the minimum detectable force by a factor near two. Finally, the remnant magnetic interaction between not completely demagnetized Ni is reduced beyond detection by using a spatial and temporal averaging of the contribution.