Nonlinear Behaviors of Three Dimensional Sloshing in the LNG Elastic Tank

Aiming at the nonlinear sloshing in the LNG tank, a three-dimensional elastic model is established to investigate the fluid structure interaction effect. For the transient flow and the tank motion, the direct coupling method is employed to calculate the interaction between the sloshing and the bulkhead. The finite element software ADINA is adopted to do the computation. The sloshing natural frequency is verified with the results of the theoretical formula. Different wall thicknesses, filling ratios and external excitations are considered and the structure natural frequency, surface elevation and sloshing pressure are obtained. The results of the elastic case are further compared with the rigid results and the nonlinear characteristics are extracted to see the hydro-elastic effect. The sloshing natural frequencies are agreed well with the theoretical results. Due to the influence of the fluid structure interaction, the couple frequencies are obviously less than those of the empty tank. With the increase of the wall thickness, the frequencies of the empty tank and the couple frequencies all increase gradually. For the surface elevation, the thinner the bulkhead thickness is, the more the high frequency component is. The free surface is relatively flat and stable in the rigid tank but tend to be chaotic for the elastic one. Due to the fluid structure interaction, the sloshing pressure of the elastic case presents obvious high-frequency fluctuation and the sloshing pressure in the elastic tank is smaller than that in the rigid tank. This model clearly shows the valuable ability to solve the three dimensional sloshing in the elastic tank.

Nonlinear dynamic response of seismically excited rectangular concrete liquid filled tanks

The effect of nonlinearity on behaviour of rectangular concrete tanks partially filled with water is studied. The nonlinearity in the numerical modeling of the surface liquid sloshing performance and hydrodynamic pressure initiates from unknown boundary conditions of contained liquid volume. The nonlinear simulations are performed for Time-History seismic analysis using the finite element software ABAQUS/CAE. The nonlinear results are compared with linear analytical solutions and ACI 350.3-06 code. A Paramedic study is conducted to investigate the effect of tank plan dimension, frequency content of different seismic ground motions, nature of earthquake movements, and interaction of bi-directional component of earthquake on the maximum sloshing height of liquid. The results reveal that the nonlinearity is more significant in shallow tanks. Moreover, nonlinear hydrodynamic pressure distribution has no important difference with linear calculated pressure except for the surface sloshing pressure acting on the top of tanks. The linear ratio of depth of liquid to tank plan dimension used in ACI 350.3-06 formulation is found to be less accurate for calculating the maximum sloshing height of liquid.

Nonlinear dynamic response of seismically excited rectangular concrete liquid filled tanks

The effect of nonlinearity on behaviour of rectangular concrete tanks partially filled with water is studied. The nonlinearity in the numerical modeling of the surface liquid sloshing performance and hydrodynamic pressure initiates from unknown boundary conditions of contained liquid volume. The nonlinear simulations are performed for Time-History seismic analysis using the finite element software ABAQUS/CAE. The nonlinear results are compared with linear analytical solutions and ACI 350.3-06 code. A Paramedic study is conducted to investigate the effect of tank plan dimension, frequency content of different seismic ground motions, nature of earthquake movements, and interaction of bi-directional component of earthquake on the maximum sloshing height of liquid. The results reveal that the nonlinearity is more significant in shallow tanks. Moreover, nonlinear hydrodynamic pressure distribution has no important difference with linear calculated pressure except for the surface sloshing pressure acting on the top of tanks. The linear ratio of depth of liquid to tank plan dimension used in ACI 350.3-06 formulation is found to be less accurate for calculating the maximum sloshing height of liquid.

Sloshing Motion in a Real-Scale Water Storage Tank under Nonlinear Ground Motion

Water storage tanks in cities are usually large and are occasionally affected by earthquakes. A sudden earthquake can cause pressure pulses that damage water containers severely. In this study, the sloshing motion in a high filling level tank caused by seismic excitation is investigated by the numerical method in a 2D model. Two well-studied strong earthquakes are used to analyze the broadband frequency nonlinear displacement of the tank both in the longitudinal and vertical directions. Based on careful experimental verification, the free surface motion and the elevations at the side wall are captured, and the sloshing pressure response is examined. The results show that the 2D section of the cylindrical tank can be used to estimate the maximum response of the 3D sloshing, and the water motions under the seismic excitations are consistent with the modal characteristics of the sloshing. The time histories response of the water motion reflected that the sloshing response is hysteretic compared with the seismic excitation. The anti-seismic ability of the damping baffle shows that its effect on sloshing pressure suppression is limited, and further study on the seismic design of water tanks in earthquake-prone regions is needed.

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.

Influencing analysis of different baffle factors on oil liquid sloshing in automobile fuel tank

Oil liquid sloshing is a common phenomenon in automobile fuel tank under variable working conditions. Installing baffles in automobile fuel tank is the most effective way to suppress adverse influence caused by oil liquid sloshing. Different types of three-dimensional finite element models filling oil liquid are created, meshed, and simulated. The reliability of simulation results is verified by test. The concept of time–area value is proposed in this work. In order to explore the influence of different baffle factors on oil liquid sloshing, six factors are studied. Six kinds of influencing factors are height, structure, shape, spacing, number, and placement of baffles. The sloshing pressure and time–area value are the core parameters for evaluating the influence degree. Some results could be obtained by comparing the parameters of oil liquid sloshing under the same condition. High baffles and baffles with small spacing have obvious attenuation influence on the pressure of oil liquid sloshing. Low baffles, double baffles, parallel baffles, and the combined action of inertia force and gravity are more beneficial to the reduction of time–area value. Time–area value is the largest and the smallest in fuel tank with intersection baffles and low baffles, respectively.

Numerical analysis on the sloshing of free oil liquid surface based on fuel tanks of different shapes

The shape of fuel tank is one of the main factors influencing oil liquid sloshing in fuel tank without baffles. The change of oil liquid sloshing pressure and free oil liquid surface area in fuel tanks of different shapes is the focus of this study. First, the reliability of the simulation method is verified by the test. Second, three different shapes of fuel tanks, which are rectangle, ellipse, and triangle, are proposed, and each shape of fuel tank is improved. A series of simulations are carried out under the same condition. The related history curves of oil liquid sloshing pressure and free oil liquid surface area are obtained, and the pressure contours of oil liquid sloshing and position diagrams of free oil liquid surface are displayed in the process of oil liquid sloshing. Finally, simulation data are compared and analyzed. In three different shapes of fuel tanks, it is found that the pressure of oil liquid sloshing in elliptical fuel tank is the biggest and time-area value of free oil liquid surface area in triangular fuel tank is the smallest. The curved bottom wall of fuel tank is beneficial to reduce the pressure amplitude of oil liquid sloshing and time-area value. All things considered, the heart-shaped fuel tank is optimal for reducing the pressure amplitude of oil liquid sloshing and evaporative emission under the same condition.

Numerical research on sloshing of free oil liquid surface based on different baffle shapes in rectangular fuel tank

Oil liquid sloshing is a normal physical phenomenon in fuel tank under variable conditions of vehicles. Installing baffles in fuel tank is an effective method to suppress oil liquid sloshing. The influence of different baffle shapes on the pressure of oil liquid sloshing and time-area value is the focus of this work. Four factors influencing the baffle shape and baffles of six different shapes are provided in this research. The pressure history curves of oil liquid sloshing at the central point and on the central line, the history curves of velocity of oil liquid mass and volume, oil liquid pressure contours, and the position diagrams of free oil liquid surface were obtained and compared in fuel tanks with baffles of different shapes. Compared with the sloshing pressure of oil liquid and time-area values in fuel tanks with baffles of different shapes, the sloshing pressure of oil liquid at the central point is the smallest in fuel tank with baffles of corrugated shape, and the sloshing pressure of oil liquid on the central line is the smallest in fuel tank with baffles of straight-line shape. However, the baffles of corrugated shape are most beneficial to reduce time-area values.

Vibration Analysis of Simply Supported Rectangular Tank Partially Filled with Water

Ground-supported tanks are used as fluid storage. One of the phenomena associated with the seismic response of liquid-filled tanks is the fluid motion occurring that causes “sloshing” at the top of free surface. This paper presents the theoretical of fluid response of rectangular tank due to horizontal acceleration of tank bottom, the impulsive and convective (sloshing) pressure and the fluid natural frequencies. The vibration analysis of fluid filled rectangular container was monitored and was evaluated in experiment for purpose to evaluation of the first frequency mode and vibration response of fluid were analysed by using FEM.