Sloshing Research Articles

Oscillons, walking droplets, and skipping stones (an overview)

This article considers additional phenomena that complement the earlier topics addressed by Ibrahim [(Liquid Sloshing Dynamics: Theory and Applications. Cambridge University Press, Cambridge, 2005), (ASME J Fluids Eng 137(9):090801, 2015)]. The first phenomenon is the localized Faraday waves known as oscillons, which were observed in granular materials and liquid layers subjected to parametric excitation. Extreme waves, known as rogue, generated in the Faraday surface ripples, are related to the increase in the horizontal mobility of oscillating solitons (oscillons), and their horizontal motion is random over a limited range of excitation acceleration amplitude. Parametric excitation of water in a Hele–Shaw cell and the associated localized standing surface waves of large amplitude will be discussed. The surface wave pattern exhibited a certain similarity with the three-dimensional axisymmetric oscillon. Faraday waves in superfluid Fermi–Bose mixtures and their wave function will be addressed in terms of position and time as described by the Schrodinger equation with time-dependent parabolic potential. The phenomenon of walking fluid droplets on Faraday waves constitutes the majority portion of this article. Different regimes of droplet motion in terms of droplet physical properties, the fluid bath excitation acceleration amplitude and frequency will be discussed. The droplet trajectory diffraction, when passes through a slit, shares the same random features of electron diffraction. The duality of the droplet-wave field together with the path-memory-driven nonlocality and other related topics will be assessed. This article is complemented with the fascinating phenomenon of the stone and bombs skipping/ricochet over water surface.

Numerical study on suppressing liquid sloshing of a rectangular tank using moving baffles linked to a spring system

In this paper, feasibility of applying moving baffles linked to a spring system as a mitigation device to suppress liquid sloshing of a container undergoing a harmonic and seismic excitation is investigated numerically using the Coupled Eulerian-Lagrangian (CEL) technique. The interaction between the Eulerian fluid domain where the material can pass through the mesh and the Lagrangian tank domain where the material is supposed to be fixed to the mesh is modelled using the CEL capability of ABAQUS software. Firstly, free sloshing of a rigid/deformable tank is achieved and the numerical results are compared with those of the experiment to validate the numerical simulation quantitatively. Secondly, liquid sloshing of a moving container in absence/presence of moving baffles is simulated and compared with those of the experimental cases qualitatively. Furthermore, the effects of various parameters namely excitation amplitude and frequency, filling ratio, spring stiffness and damping coefficient on both the sloshing kinetic energy and normal forces exerted on the tank wall are investigated separately. The results show that the spring stiffness effects on the kinetic energy of liquid sloshing is minor while the normal force exerted on the left wall can be highly influenced by the spring stiffness.

Numerical analyses of liquid slosh by Finite volume and Lattice Boltzmann methods

Liquid slosh phenomenon has been widely observed in aerospace and aeronautic engineering. In this paper, Finite volume method (FVM) and Lattice Boltzmann method (LBM) are proposed to perform the quick evaluation of liquid slosh behaviour under different container designs. The effectiveness of the numerical models is validated by the existing experimental data. The validated models are then used to study the fuel slosh behaviour with different baffle ring designs. By inserting the baffle to divide the liquid region into multiple sections, the slosh motion of the liquid is suppressed. At the same time, the effectiveness and time efficiency of LBM model have been demonstrated by a parallel comparison with the results from the FVM model. It is found that the computational time cost of LBM model is only around 7.0% of the time cost for FVM model without compromise of the numerical accuracy. This supports the future utilisation of LBM model in quick design evaluation of slosh-like problem.

수평 배플이 설치된 사각 용기 내 슬로싱의 입력성형 기반 제어

Suppression of liquid sloshing in moving tanks is essential in many engineering applications. The sloshing can be successfully suppressed by installing baffles inside the tank or applying a control theory called ‘input shaping’ to the tank velocity profile. This study aims to numerically investigate the combined effect of horizontal baffles and input shaping on sloshing in a horizontally moving tank. Numerical simulations are carried out for the two-phase flow of water and air using a volume-of-fluid(VOF) model. Results show that the damping effect of baffles strongly depends on the baffle height but input shaping provides additional control capability for all the baffle heights considered.

Numerical simulation of two-layered liquid sloshing in tanks under horizontal excitations

A numerical model NEWTANK has been developed to study two-layered liquid sloshing under horizontal external excitations. The model solves spatially averaged NSEs on a non-inertial coordinate for external excitations. The two-step projection method is employed in numerical solutions, and the Poisson equation for pressure field is solved by Bi-CGSTAB technique. A multi-layered volume-of-fluid method is proposed to track both free surface and interface between layered liquids simultaneously. In order to validate the accuracy of the model, the simulated results of sloshing responses are compared with linear analytical solutions and experimental data. Good agreements are obtained when response amplitude is within linear regime. However, when nonlinearity becomes strong, deviation from analytical solution will be large due to nonlinear energy transfer from the primary mode to higher modes. Further investigation reveals that for two-layered liquid sloshing, there exist two natural frequencies with the smaller one related to response of lower layer liquid and the larger one upper layer. Therefore, different external excitation frequencies may induce upper-layer resonance, lower-layer resonance or resonances of both layers, each of which exhibits very different patterns of energy transport between modes and layers. Finally, a violent 3-D sloshing with broken free surface and interface is simulated and discussed.

The Interface Motion and Hydrodynamic Shear of the Liquid Slosh in Syringes.

Interface motion and hydrodynamic shear of the liquid slosh during the insertion of syringes upon autoinjector activation may damage the protein drug molecules. Experimentally validated computational fluid dynamics simulations are used in this study to investigate the interfacial motion and hydrodynamic shear due to acceleration and deceleration of syringes. The goal is to explore the role of fluid viscosity, air gap size, syringe acceleration, syringe tilt angle, liquid-wall contact angle, surface tension and fill volume on the interface dynamics caused by autoinjector activation. A simplified autoinjector platform submerged in water is built to record the syringe and liquid motion without obstruction of view. The syringe kinematics is imported to the simulations based on OpenFOAM InterIsoFoam solver, which is used to study the effects of various physical parameters. The simulations agree with experiments on the air-liquid interface profile and interface area. The interfacial area and the volume of fluid subject to high strain rate decrease with the solution viscosity, increase with the air gap height, syringe velocity, tilt angle and syringe wall hydrophobicity, and hardly change with the surface tension and liquid column height. The hydrodynamic shear mainly occurs near the syringe wall and entrained bubbles. For a given dose of drug solution, the syringe with smaller radius and larger length will generate less liquid slosh. Reducing the air volume and syringe wall hydrophobicity are also helpful to reduce interface area and effective shear. The interface motion is reduced when the syringe axis is aligned with the gravitational direction.

Experimental study of particle migration under cyclic loading: effects of load frequency and load magnitude

The study of particle migration in porous media under cyclic loading is the key to understand the mechanism of mud pumping hazard in railway embankments. This paper presents a series of particle migration tests, in which soil particles migrate into an overlying gravel layer under cyclic loading. The results show that the increase in loading frequency and load magnitude leads to more particle migration upwards at a greater rate, implying that the train speed and axle loads affect the extent of mud pumping. The slurry turbidity in the gravel layer increases to a steady state value with time. Soil particles smaller than 5 μm have the potential to diffuse into the entire gravel layer, and larger particles tend to aggregate in the bottom layer of the gravel. The backward erosion gradually develops deeper into the soil layer, and there is a maximum erosion depth associated with each load frequency and load magnitude. As for the mechanism, the pore water pressure oscillates because of liquid sloshing. Its amplitude is much larger in the gravel layer than that in the soil layer due to their difference in permeability. The axial hydraulic gradient acts as a pumping effect to stimulate the migration of soil particles. Increasing load frequency is conducive to the generation of a stronger pumping effect at the gravel–soil interface. Increasing load magnitude does impact not only the extent of pumping effect, but also the development of an interlayer which plays an important role in promoting particle migration.

Two Phase Linear Quadratic Gaussian Controller Design for Launch Vehicle Autopilot

The achievable payload of a launch vehicle is sensitive to the mass of the terminal stage which injects the payload into orbit, as well as to tracking errors introduced by the autopilot. The system is usually characterized by lightly damped slosh modes with uncertain parameters, whose stabilization is critical, while maintaining the overall performance of the system. Passive slosh stabilization involves introduction of mechanical baffles into the fluid tanks, which impacts the achievable payload mass. Optimal tracking performance along with active slosh stabilization is hence an ideal combination of autopilot design objectives. While optimal control methods are attractive for such systems, the lack of physical insight in the design procedure often limits the usefulness of these methods for launch vehicle autopilot design. A major challenge in stabilizing lightly damped slosh is the necessity to cater to very large mode magnitudes and phase swings exhibited by the system over the range of parameter perturbations. The significant contribution of this paper is the development of a two phase Linear Quadratic Gaussian approach, utilizing the physical insight into the system performance for tuning the weights in the performance index, to satisfy the time domain as well as frequency domain objectives. A robust design which exhibits superior time domain as well as frequency domain performance as compared to the benchmark classical controller is obtained, with near perfect phase stabilization of the lightly damped slosh dynamics.

Study of the effect of baffles on longitudinal stability of partly filled fuel tanker semi-trailer using CFD

Sloshing of liquid in partially filled fuel tanker vehicles has a strong effect on the directional stability and safety performance. Under the maneuver of the vehicle, such as steering, braking, or accelerating, the liquid fuel in the tanker tends to oscillate. As a result, hydrodynamic forces and moments raise. It leads to reduce the stability limit and the controllability of the vehicle. To minimize the effect of sloshing, the baffles are usually added to the tanker. This paper presents the study of the effect of baffles on the longitudinal stability of the fuel tanker semi-trailer using the computational fluid dynamics (CFD) approach. A three-dimensional fluid dynamic model of a typical tanker with different baffle configurations is developed. The User Defined Function (UDF) is used to control the acceleration of the tanker according to the simulation scheme. Transient simulations are performed for the cases of constant acceleration longitudinal maneuvers with different levels of fuel in the tanker. The volume of fluid (VOF) and air obtained from the simulation is used to indirectly calculate the center of gravity of the tanker. The post-processing results show that the baffles could provide resistance to the fluid sloshing, resulting in an improvement of the longitudinal stability of the tanker semi-trailer. The results also prove that the benefit of the baffle to the fuel tanker vehicle’s stability depends on the size of the baffle, as well as the number of baffles. The 40% height three baffles model is the proper baffle model to resist the longitudinal sloshing in the partially filled tanker of the studied trailer. By adding baffles, shifting of load on the kingpin and the rear axis are less than 5% and 2% as the tanker is filled with 50% and 70% fluid level respectively.

Numerical and experimental analysis of the effect of elastic membrane on liquid sloshing in partially filled tank vehicles

A numerical analysis for fluid-membrane interaction is conducted to investigate fluid slosh within a partially filled horizontal cylindrical tank with an elastic membrane restraining the free surface. The fluid-membrane interaction analysis is performed to investigate the effect of membrane on liquid slosh responses in terms of liquid load shifts, slosh forces, moments and slosh frequency. A series of experiments were conducted on a scaled horizontal cylindrical tank with an elastic membrane-like restraint under harmonic acceleration excitations in longitudinal or lateral direction. The validity of the numerical model is demonstrated using the laboratory-measured data. The validated model is subsequently formulated for a full scale tank and analysis are performed under excitations idealizing the straight-line braking or turning maneuvers to investigate the antislosh effectiveness of membrane. It is shown that the addition of membrane can yield substantial reduction in slosh amplitude and thus the pitch and roll moment; the slosh frequency can be substantially shifted to higher values to avoid resonance in partly filled tanks.

Running safety evaluation of a 350 km/h high-speed freight train negotiating a curve based on the arbitrary Lagrangian-Eulerian method

To adapt to the rapid growth of the logistics market and further improve the competitiveness of railway transportation, the high-speed freight train with a design speed of 350 km/h is being developed in China. The safety of the train under great axle load of 17 t and dynamic load is unknown. This paper is aimed to study the running safety of the high-speed freight train coupled with various cargo loading conditions negotiating a sharp curve at high velocity. A numerical model integrated a fluid-structure coupled container model and the nonlinear high-speed freight train was set up by the software of LS-DYNA. The fluid-structure interaction model between the container and fluid cargo was established using the Arbitrary Lagrangian-Eulerian (ALE) method. Two influencing parameters, including the cargo state in the container and the fill level, were selected. The study results showed that the wheelset unloading ratio and overturning coefficient could be significantly affected by the liquid sloshing, while the influence of sloshing on the risk of derailment was slight. In general, increasing the cargo filling rate would contribute to vehicle operation safety. In conclusion, this study would provide theoretical help for the running safety of the newly designed high-speed freight train.

Numerical Simulation on the Sloshing Characteristics of Gasliquid Flow in Cargo Tank and Anti-sloshing Methods

With the rapid development of society, the demand for liquid carrier ships and vehicles is increasing rapidly. Under the action of external load, the liquid in the tank would move relative to different degrees and produce hydrodynamic pressure on the local part of the liquid bulkhead, which will cause local damage or complete destruction of the structure, and then lead to leakage or other safety accidents. In this paper, computational fluid dynamics method is used to simulate the sloshing characteristics of the liquid in the cargo tank, and the instantaneous characteristic data of the free surface displacement fluctuation of the sloshing liquid are monitored. Through the pressure acquisition system, the hydrodynamic pressure distribution acting on the side wall of the cargo tank under external excitation is obtained. Through the free surface displacement fluctuation and the maximum hydrodynamic pressure acting on the side wall, the severity of liquid sloshing in cargo tank under external excitation is evaluated. The effects of different baffle combinations on liquid sloshing in cargo tanks are studied and discussed. The effects of baffles with holes on liquid sloshing are also discussed.

The sloshing law of liquid surface for ground rested circular RC tank under unidirectional horizontal seismic action

Abstract The dynamic characteristics and liquid sloshing of a circular tank are analysed using ADINA software through seismic response analyses. The maximum sloshing wave height for the circular tank under unidirectional horizontal seismic action is developed. The calculation method involves three parameters such as tank radius, seismic coefficient and dynamic coefficient. The dynamic coefficient of liquid sloshing is determined corresponding to the long-period seismic design β spectrum with a 5% damping ratio using basic sloshing period. The established method can guide the seismic design of liquid-containing structures. The established method of calculating sloshing wave height is compared with those in the American code.

Guidance Navigation and Control for Chang’E-5 Powered Descent

To achieve the goal of collecting lunar samples and return to the Earth for the Chang’E-5 spacecraft, the lander and ascender module (LAM) of the Chang’E-5 spacecraft successfully landed on the lunar surface on 1 Dec., 2020. The guidance, navigation, and control (GNC) system is one of the critical systems to perform this task. The GNC system of previous missions, Chang’E-3 and Chang’E-4, provides the baseline design for the Chang’E-5 LAM, and the new characteristics of the LAM, like larger mass and liquid sloshing, also bring new challenges for the GNC design. The GNC design for the descent and landing is presented in this paper. The guidance methods implemented in the powered descent are presented in detail for each phase. Propellant consumption and hazard avoidance should be particularly considered in the design. A reconfigurable attitude control is adopted which consists of the quaternion partition control, phase and gain stabilization filter, and dual observer. This controller could provide fast attitude maneuver and better system robustness. For the navigation, an intelligent heterogeneous sensor data fusion method is presented, and it is applied for the inertial measurement unit and velocimeter data. Finally, the flight results of the LAM are shown. Navigation sensors were able to provide valid measurement data during descent, and the thrusters and the main engine operated well as expected. Therefore, a successful soft lunar landing was achieved by the LAM.

Dynamic response of concrete tanks under far-field, long-period earthquakes

The dynamic responses of rectangular concrete liquid-storage tanks under near-field and far-field, long-period (FFLP) earthquakes were comparatively studied using a shaking table. The effects of different seismic reduction methods were compared and the influence of limiting devices on sliding isolation was evaluated. Under a FFLP earthquake, the results showed that liquid sloshing was more likely to exhibit non-linear behaviour. Greater sloshing occurred in tanks with rubber isolation and sliding isolation with the spring limiting device than in the other types of tank. These two damping measures actually increased the sloshing height. Sliding isolation with the steel-bar limiting device significantly reduced the sloshing height, and sliding isolation produced greater horizontal displacement. However, the influence of a FFLP earthquake on other liquid sloshing responses was not remarkable. Sliding isolation with the steel-bar limiting device was found to have the most beneficial effect.

Sloshing analysis and mechanical modeling of liquid cargo during lifting

Abstract When the acceleration of the liquid-filled container undergoes a step change, liquid sloshing is prone to occur. A sloshing linear dynamic model is put forward to predict the position change of center of mass of sloshing liquid. This modeling process uses a liquid static model and adds a time variable. The numerical simulation example finally verifies the feasibility of the mathematical model and shows that linear dynamic model has the ability to predict the displacement of the center of mass.

해석 기법 별 유체 슬로싱 현상에 대한 비교 분석

In a swaying tank partially filled with liquid, inertia of the liquid exerts body force on itself, causing a periodic motion of the free surface of the liquid. This might cause the tank sway, which leads to structural damages of it. This phenomenon is called “Liquid Sloshing.” Many researches on liquid sloshing including experiments were conducted through numerical methods like Finite Volume Method(FVM), Finite Element Method(FEM), and Smoothed Particle Hydrodynamics(SPH) Method and so on. Except for particle-based numerical methods, other numerical methods are required to simulate free surface shape of liquid. These grid-based methods use Volume of Fluid method(VOF) or Level-set method to imitate the free surface shape.<BR> In this Paper, It aims to simulate sloshing phenomena of 3-dimensional rectangular tank. FVM and VOF method, FEM and Level-set method, and a particle-based solver with SPH method are used for analyzing sloshing motions. The CFD results are compared with experimental data and other published computational data. The details of time history pressure data on the tank wall and the free surface shape are discussed to find characteristics of the numerical methods.

H∞ Control Design for a Rigid-Flexible Spacecraft under a Fuel Slosh Influence

The spacecraft Attitude Control System (ACS) performance and robustness depend on the interactioneffects between the fuel slosh motion, the panel's flexible motion, and the spacecraft rigid motion, mainly duringtranslational and/or rotational maneuvers. In regards to satellite pointing accuracy flexibility and fuel, slosh is thetwo most important effects that should be considered in the satellite ACS design since their interactions can damage the ACS performance and robustness. Once, the lowest vibration frequencies, normally of the sloshing modeare about six times less than of the ACS bandwidth. Therefore, there is a strong possibility that this mode can destabilize the ACS pointing accuracy. This phenomenon is called spillover because the control effort spills over outside the control bandwidth. As a result, the designer needs to explore the limits between the conflicting requirements of performance, that is, increase of the bandwidth without introduction noise in the ACS keeping the systemrobustness to parameters variation. In this paper, one applies the H infinity control method which can deal withthese two design requirements (performance and robustness) considering the controller error pointing that may belimited by the minimum time necessary to suppress disturbances that affect the satellite attitude acquisition. Theequations of motions are obtained considering the Lagrange method for small flexible deformations and a mechanical model of liquid sloshing which allows modeling and investigating the longitudinal dynamic characteristics of apartially filled liquid tank during a pitch maneuver, satisfying performance and robustness requirements.

Effects of different damping baffle configurations on the dynamic response of a liquid tank under seismic excitation

The dynamic motion of liquid sloshing in a container due to an external excitation can cause pressure pulses that severely damage the structure. In this study, a 2D rectangular tank was used to numerically model the hydrodynamic characteristics of sloshing and the pressure response in a typical industrial container. Harmonic and ground motion excitations were considered, and seven recorded ground motions were used to simulate the pressures at specified monitoring points. The contributions of the filling depth, ground motion components, and damping baffle to the pressure response history under impulsive and convective mode were examined. Based on the analysis of the dynamic response, a suitable damping baffle system was developed for all seismic excitations. The results of this work contribute toward improving tank design in earthquake-prone regions of the world.

An Innovative Method for Sloshing Analysis of a Partially-Filled Tank Wagon in Braking Using a Coupled Vehicle/Fluid Model

An Innovative Method for Sloshing Analysis of a Partially-Filled Tank Wagon in Braking Using a Coupled Vehicle/Fluid Model