Snapping elastic disks as microswimmers: swimming at low Reynolds numbers by shape hysteresis

An elastic disk with a snapping transition triggered by local swelling swims in a viscous fluid at low Reynolds numbers because of the hysteretic nature of the snapping transition.

Dynamic Analysis of Flexible Shaft and Elastic Disk Rotor System Based on the Effect of Alford Force

Taken the flexible shaft and elastic disk rotor system as the research object, vibration differential equations are established by the modal synthesis method. Based on the Runge–Kutta method of direct integration, dynamic equations are solved successfully. Then, the effects of Alford force caused by the airflow excitation are researched on the stability and dynamic response. The results show modal vibration of the disk takes a great effect on the coupled natural frequency of shaft transverse vibration in the high rotational speed region. The effect of shaft-disk coupling makes rotor frequency to decrease, and different rotational speeds have little effect on rotor frequency. Eccentric distance is sensitive to the amplitude of rotor response, but it has little effect on rotor stability, motion law, and relative relationship of two response frequencies. The proportion of rotor responses caused by aerodynamic excitation force becomes larger with the increase of rotational speed and disk radius. However, the proportion decreases with the second support moving to the right, and it is helpful for the stable operation of the rotor system.

The Damped Eigenfrequency Analysis for an Elastic Disk Clamped by a Water-Filled Cylinder

A vibroacoustic testing model in laboratory for the damped eigenfrequencies and eigenmodes is introduced in this paper. The unsymmetric (u, p) variational formulas are implemented for three dimensional structures based on the elastodynamic displacement field u and the fluid acoustic pressure field p. The damping coefficients of materials seem to have no obvious effect on the coupled numerical model. Then the damped eigenfrequencies can alternately be obtained by vibration signal analysis method. The Fast Fourier Transform for the spectrum domain analysis illustrates an effective means to evaluate the damped eigenfrequencies.