Nonlinear multimodal model for an annular tuned sloshing damper equipped with damping screens

Annular tuned sloshing dampers equipped with damping screens are studied experimentally and analytically. A nonlinear multimodal model is presented to simulate the coupled response among the lowest order sloshing modes in a tank equipped with damping screens, which leads to velocity-squared damping. Shake table tests are conducted on annular tanks with various inner radii, water depths, screen orientations, and base excitation amplitudes. The proposed model is evaluated by comparing the predicted and measured sloshing forces, energy dissipation per cycle, and wave heights. The predicted sloshing forces and energy dissipation per cycle are in good agreement with the measured results. The wave heights show larger discrepancies, including phase shifts; however, the peak amplitudes are captured with reasonable accuracy for the tests conducted. Secondary resonances lead to multiple peaks in the frequency response plots when higher order sloshing modes become excited through modal coupling. Plots created to indicate which secondary resonances are likely to occur for a given liquid depth ratio indicate that it may not be possible to avoid all secondary resonances. Radial damping screens can be strategically positioned within the tank to provide the desired level of damping to the fundamental sloshing modes, as well as a reasonable amount of damping to higher order modes that are susceptible to secondary resonance excitation. Since existing linearized models for annular tuned sloshing dampers equipped with damping screens do not capture the important nonlinear response characteristics of these devices, the proposed model fills an important research gap necessary to facilitate their effective design.

Experimental and Numerical Study of Stratified Sloshing in a Tank under Horizontal Excitation

The density-stratified liquids horizontal sloshing was tested on a vibration table, and a series of laboratory experiments have been performed to analyze the influence of the excitation frequency on density-stratified liquids sloshing in a partially filled rectangular tank. The MultiphaseInterFOAM solver in OpenFOAM was employed to simulate two-layer fluids sloshing problems. The numerical results of dynamic pressure were validated against the experimental data, showing that the employed model can accurately simulate the stratified liquids sloshing phenomenon. Effects of two-layer fluids liquid depth ratio and total liquid depth on stratified sloshing characteristics were discussed in detail. The response law of the maximum interfacial wave elevation to external excitation frequency was presented in this study. The evolution of the velocity field of density-stratified liquids sloshing is also studied.

A smooth polynomial shaped command for sloshing suppression of a suspended liquid container

A smooth polynomial shaped command with an adjustable command time length is proposed for eliminating the residual vibrations of a multi-mode system. The ability of eliminating jerks and vibrational modes, regardless of their number, offers the most advantage of the proposed command. A numerical simulation is conducted to test the command’s effectiveness by eliminating the residual sloshing oscillations of a liquid-filled container conveyed by an overhead crane in a rest-to-rest manoeuvre. The governing equations of the liquid free-surface level are derived by modelling the sloshing dynamics by a series of mass–spring–damper harmonics. The proposed model accounts for the coupling between the pendulum dynamics and the sloshing equivalent mechanical model. The command’s robustness to the system parameters’ uncertainties, liquid depth and cable length, are investigated as well. The ability of adjusting the command length and retaining higher sloshing modes in command-designing are also outlined.

Command Shaping for Sloshing Suppression of a Suspended Liquid Container

The residuals of liquid free-surface wave oscillations induced by a rest-to-rest crane maneuver of a suspended liquid container are eliminated using a command-shaped profile. The dynamics of liquid sloshing are modeled using an equivalent mechanical model based on a series of mass-spring-damper systems. The proposed model considers the excited frequencies of the container swing motion and liquid sloshing modes. The objective is to design a discrete-time shaped acceleration profile with a variable command length that controls the moving crane-jib, while suppressing the sloshing modes. Simulations are conducted to illustrate the command effectiveness in eliminating liquid sloshing with a wide variation range of system and command-designing parameters; liquid depth, cable length, command duration, and the employing of higher sloshing modes in representing the sloshing dynamics. The command sensitivity of the input command to changes of the system parameters are treated as well. A refined and smooth input command based on suppressing the residuals of multimodes is also introduced. Furthermore, the command effectiveness was supported by a comparison with the time-optimal flexible-body control and multimode zero vibration input shaper.

Effect of Laser Energy on Optical and Morphological Properties of Gold Nanoparticles

Noble metals gold NPs are produced by pulsed (“Q-switched, 1064 nm Nd: YAG”) ablation of gold foil dipped in doubles distilled water DDW by laser. (PLAL) the process was performed with laser energy in range (400–700) mJ at (90 pulses, wavelength 1064 and room temperature and liquid depth 9 mm. The influence of laser energies have been tested structurally, optically and morphologically and examined by using scanning electron microscope (SEM), UV-visible spectroscopy and atomic force microscope (AFM). The absorption spectra of AuNPs are prepared in water piercing and solitary peaks nearby 518 and 524 nm, demonstrating the assembly of clean and sphericals in shape AuNPs with the middling size in the range of (20–50) nm. SEM and AFM have established all the measurements of size.

Effect of porous baffle on sloshing pressure distribution in a barge mounted container subjected to regular wave excitation

An experimental study has been carried out to assess the sloshing pressure expected on the side walls of the tank and on top panel. A liquid fill level with an aspect ratio (hs /l, where hs is the static liquid depth and l is the tank length) of 0.488 is considered which corresponds to 75% liquid fill level. In view of suppressing sloshing oscillation and consequent sloshing pressure, the baffle wall configurations such as porous wall at l/2 and porous walls at l/3 and 2l/3 were adopted. Three porosities of 15%, 20.2%, and 25.2% were considered. The sloshing tank is fitted into the freely floating barge of model scale 1:43. The barge is kept inside the wave flume in the beam sea conditions. The effects of wave excitation frequencies and on the sloshing pressure variation have been studied in detail. For comparison purpose, solid wall placed at l/2 (Nasar and Sannasiraj, 2018) is also considered and, the salient results are herein reported.