Narrow Results

The vibration reduction for a cantilever beam with an interior sloshing absorber is numerically simulated using an implicit coupling approach of segregated solvers. The sloshing liquid damps the vibration by allowing the sloshing force to lag behind the displacement phase of the beam. The sloshing in the absorber is analyzed both theoretically and numerically. The results show that the impact of free sloshing on the forced sloshing causes the phase to be lagged behind when the free frequency is lower than the frequency of forced vibration. A range of values are considered for the parameters of the absorber and system vibration in the simulations to investigate their effects on the suppression capability of the absorber. In order to explain the effects of the parameters, two new parameters γ and κ are defined to represent the phase lag and magnitude of the sloshing force, respectively. Their applicability is confirmed by a series of numerical simulations. The results reveal the main mechanism of vibration suppression, providing a theoretical basis for optimizing the design of the interior absorber.

Utilizing the inherent capacity of energy dissipation, liquid tanks are nowadays being employed as tuned liquid dampers (TLDs) for controlling unwanted structural vibration. The effective liquid mass that participates in convective mode controls the tank’s overall dynamic response. The stagnant liquid mass, which does not participate in sloshing at the bottom corners of the conventional rectangular and cylindrical TLDs, increases the total liquid mass and has no role in the vibration control of the supporting structure. The hydrodynamic behavior of the sloped wall tank under resonance conditions is demonstrated under harmonic excitation over a range of frequencies close to the fundamental sloshing frequency of the tank. However, the present study focuses on the effect of the modified geometrical configuration due to the bottom-mounted object on the slosh displacement and hydrodynamic base shear. A 2D finite element model developed employing the potential flow theory is used for the present numerical investigation. Compared to a conventional flat-bottom tank, the sloped wall tank exhibits a considerable increase in hydrodynamic base shear near resonance excitation. The dynamic impulsive and the convective response components of the base shear force have been successfully estimated. Also, the effectiveness of the proposed sloped wall tank with bottom-mounted internal object is examined under EL-Centro EW earthquake motion.

In this paper, we present an extended ghost fluid method (GFM) for computations of liquid sloshing in incompressible multifluids consisting of inviscid and viscous regions. That is, the sloshing interface between inviscid and viscous fluids is tracked by the zero contour of a level set function and the appropriate sloshing interface conditions are captured by defining ghost fluids that have the velocities and pressure of the real fluid at each point while fixing the density and the kinematic viscosity of the other fluid. Meanwhile, a second order single-fluid solver, the central-weighted-essentially-nonoscillatory(CWENO)-type central-upwind scheme, is developed from our previous works. The high resolution and the nonoscillatory quality of the scheme can be verified by solving several numerical experiments. Nonlinear sloshing inside a pitching partially filled rectangular tank with/without baffles has been investigated.

The aim of this work is to study the hydrostatic pump created under liquid sloshing in a rectangular tank partially filled with liquid. A numerical simulation was performed to predict the liquid motion in the tank. The apparition of the compression and the depression zones due to the liquid motion was presented and analyzed. An experimental setup with sinusoidal movement was developed to study the hydrostatic pump. The hydrostatic pump is created using a mixing element. The experimental results show that the compression and the depression zones can create the hydrostatic pump. The effect of the connecting chamber value was studied for different values of external excitation frequency. The pump depends considerably on the dimension of the connecting zone between the two volumes. For the different connecting chamber values, the pumped quantity increase with the increase of the frequency.

Sloshing liquid dampers (SLDs), popularly known as tuned liquid dampers, are used as passive control devices for reducing structural vibrations resulting from wind and earthquake excitations in tall buildings and high-rise structures. Available research studies on these dampers mostly deal with single-degree-of-freedom (SDOF) structures although tall buildings and high-rise structures are generally multi-degree-of-freedom (MDOF) structures. In the present investigation, effectiveness of these SLDs has been studied for MDOF building structures. Five-storied shear buildings have been considered as representative of MDOF structures. It is shown that the liquid sloshing is the most important design parameter, rather than tuning of the fundamental sloshing frequency to the structure frequency, for the liquid damper to be effective. Furthermore, the liquid damper design for multistory buildings is different from that for SDOF structures, where not only the optimal tuning ratio of the liquid damper is different, but multiple dampers located at critical locations are required for effective control of floor accelerations. Finally, it is illustrated that SLDs, if appropriately designed, can be very effective in reducing overall force, floor acceleration, and deformation responses of MDOF building structures for broad-band earthquake type base excitations.

The violent dynamic behavior of liquid under horizontal excitation is a key factor that needs to be addressed in the seismic-resistant design of liquid tanks. Therefore, this study focuses on the slosh response of the liquid medium in a rectangular tank under Imperial Valley 1979, El Centro 1940 and Kobe 1995 ground motions of different frequency ranges. The ground motions records are selected based on the PGA/PGV ratio. For slosh control, a single vertical perforated baffle plate is used as an anti-slosh element with different configurations of perforations. Considering the free surface elevation as the major response parameter, the effect of percentage of perforation of the baffle plate, clear spacing of perforations and offset distance of the perforated plate are investigated by carrying out the pressure-based transient analysis using computational fluid dynamic (CFD). The optimum perforation varies from 10% to 17%, corresponding to the frequency of ground motion in the range of far-resonant to near-resonant conditions. Additionally, “rapid zone” ($R$-zone) and “moderate zone” ($M$-zone) are identified to pilot the positioning of the perforated baffle plate in liquid tanks. The perforated baffle plate with an optimum range of moderately spaced perforations positioned at the moderate zone of the tank effectively reduces the free surface elevation. Furthermore, the perforated baffle plate is more advantageous during violent sloshing under near-resonant conditions.

In a laterally excited, partially liquid-filled U-shaped container, oscillation is the predominant motion of the liquid. However, there would be some sloshing in the liquid free surface at the vertical limbs of the container. Due to the presence of high-energy velocity pulses, near-fault ground motions can cause significant sloshing in the vertical limbs of the container. Thus, it is necessary to examine the effect of near-fault earthquake excitations on the sloshing liquid height, sloshing-induced hydrodynamic pressure, and shear stress at the walls of the U-shaped containers. The same is attempted in this paper. The standard “k-epsilon” turbulence model with enhanced wall function is considered in this study. The outcome of this study reveals that the time-wise frequency variation of the near-fault ground motions significantly affects the sloshing response of the liquid stored in the U-shaped containers. It is observed that the sloshing-induced hydrodynamic pressure is severely influenced by the frequency content of the ground motion records rather than their peak ground acceleration.