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Added mass
About: Added mass is a research topic. Over the lifetime, 2849 publications have been published within this topic receiving 47899 citations.
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26 citations
TL;DR: In this paper, two types of floating bridges, discrete-pontoon floating bridges and continuous-ponoon floating bridge, were subjected by moving loads to study the dynamic responses with hydrodynamic influence coefficients for different water depths.
Abstract: There are two types of floating bridge such as discrete-pontoon floating bridges and continuous-pontoon floating bridges. Analytical models of both floating bridges subjected by moving loads are presented to study the dynamic responses with hydrodynamic influence coefficients for different water depths. The beam theory and potential theory are introduced to produce the models. The hydrodynamic coefficients and dynamic responses of bridges are evaluated by the boundary element method and by the Galerkin method of weighted residuals, respectively. Considering causal relationship between the frequencies of the oscillation of floating bridges and the added mass coefficients, an iteration method is introduced to compute hydrodynamic frequencies. The results indicate that water depth has little influence upon the dynamic responses of both types of floating bridges, so that the effect of water depth can be neglected during the course of designing floating bridges.
26 citations
TL;DR: In this paper, the effect of a two-dimensional compound gust is considered, defined as the variation of both axial and lateral flow disturbances, and the force histories of gust-induced loads on a flat-plate model were compared to those on an equivalent model accelerated within a uniform flow.
26 citations
TL;DR: In this article, a spring-mass oscillator submerged in quiescent fluid subject to periodic changes in its volume is investigated and a quasi-linear relationship is found to link the terminal amplitude of the oscillations to the extent of size change.
Abstract: A submerged body subject to a sudden shape-change experiences large forces due to the variation of added-mass energy. While this phenomenon has been studied for single actuation events, application to sustained propulsion requires studying \textit{periodic} shape-change. We do so in this work by investigating a spring-mass oscillator submerged in quiescent fluid subject to periodic changes in its volume. We develop an analytical model to investigate the relationship between added-mass variation and viscous damping and demonstrate its range of application with fully coupled fluid-solid Navier-Stokes simulations at large Stokes number. Our results demonstrate that the recovery of added-mass kinetic energy can be used to completely cancel the viscous damping of the fluid, driving the onset of sustained oscillations with amplitudes as large as four times the average body radius $r_0$. A quasi-linear relationship is found to link the terminal amplitude of the oscillations $X$, to the extent of size change $a$, with $X/a$ peaking at values from 4 to 4.75 depending on the details of the shape-change kinematics. In addition, it is found that pumping in the frequency range of $1-\frac{a}{2r_0}<\omega^2/\omega_n^2<1+\frac{a}{2r_0}$ is required for sustained oscillations. These results on the unsteady fluid forces produced by shape-changing bodies provide a foundation for the design and control of soft-bodied underwater vehicles.
26 citations
TL;DR: In this paper, the authors discussed the method of substituting equivalent nonlinear viscous element for linear viscous elements in the optimum control system and validated the proposed method through numerous time history analyses over a wide range of mass ratio (added mass/main mass), and phases and spectrum characteristics of earthquakes.
Abstract: We have already proposed optimum response control method of the system using linear viscous element with inertial mass connected in series to a linear elastic bracing element. In this paper, we discuss the method of substituting equivalent nonlinear viscous element for linear viscous element in the optimum control system. The proposed method is validated through numerous time history analyses over a wide range of mass ratio (added mass/main mass), and phases and spectrum characteristics of earthquakes.
26 citations