Sloshing Research Articles

Performance assessment and optimisation of a concentric two-piston compressor system for hydrogen storage

The ionic compressor has a prospective application potential for the conversion of mechanical energy into internal energy in high-pressure hydrogen as the ionic liquid can separate the metal piston and the hydrogen gas. The sloshing of the liquid inside is inevitable in such a liquid piston compressor, which has an impact on the specific energy consumption of the hydrogen compression. The thermofluid behaviour of this liquid sloshing can be effectively influenced by the baffle structure and piston trajectory. A novel concentric two-piston compressor is proposed in this paper, which has a unique structure that can act as a baffle inside and actively influences the fluid flow by adjusting the piston trajectory. The quantitative influence of key structural design factors on the compressor performance is investigated by mathematical modelling, based on which the optimal structural design was obtained by Taguchi and analysis of variance methods. Results indicate that the diameter ratio of Piston A to Piston B is the dominating factor for both the mass delivered and the specific energy consumption. With the optimal design in the structure, the specific energy consumption is found as 2328.49 kJ/kg, where the mass delivered and power consumption are observed as 21.42 kg/h and 13.86 kW, respectively.

Vibration response analysis of mobile liquid Pb-Bi micro-reactors under transportation with liquid sloshing

Mobile micro-reactors, which used the liquid lead–bismuth eutectic (LBE) as coolants, providing energy to remote regions had become a popular topic in nuclear energy due to their desirable characteristics, including inherent safety and modularity. However, the liquid sloshing effect in a reactor may exhibit fluid–structure interaction (FSI) coupling effects, which could have a significant impact on the relevant internal systems. And the ratio of coolant in liquid to solid form was correlated with the duration of heat dissipation. This paper aimed to investigate the liquid sloshing effect in a micro-reactor that was subject to vehicle vibrations, the objective was to provide recommendations for transportation scenarios involving various liquid sloshing. To achieve this, a full-vehicle dynamic model of the system was developed using multi-body dynamics. Additionally, MATLAB simulation software was utilized to simulate the road roughness loadings that the micro-reactor may encounter during transportation. Moreover, a finite element numerical model of the Mobile Micro-reactor had been developed in order to simulate the sloshing effect that occurred during transportation, the numerical models presented in this study were validated by comparing them with a previously-verified Housner model that involved a cylindrical tank. This study investigated the sloshing effects of the Mobile Micro-reactor under different liquid–solid ratios of coolant, internal component lengths, and liquid surface heights. The results indicated that the internal components within the reactor vessel can alleviate the sloshing effect. The solid ratios of liquid lead–bismuth coolant and the liquid surface height during transportation had an impact on the sloshing effect. These findings provided valuable insights for studying the sloshing response of on-board reactors during liquid sloshing transportation.

Liquid Sloshing in Soil-Supported Multiple Cylindrical Tanks Equipped with Baffle under Horizontal Excitation

The dynamic behavior of liquid storage tanks is one of the research issues about fluid–structure interaction problems. The analysis errors of the dynamics of multiple adjacent tanks can exist if neglecting soil–tank interaction since tanks are typically supported on flexible soil. In the present paper, the dynamics of a group of baffled cylindrical storage tanks supported on a circular surface foundation and undergoing horizontal excitation are analytically examined. For upper multiple tank–liquid–baffle subsystems, accurate solutions to the velocity potential for liquid sloshing are acquired according to the subdomain partition technique. A theoretical model is utilized to portray the continuous sloshing of each tank. For the soil–foundation subsystem, a lumped-parameter model is used to characterize the impacts of soil on upper-tank structures using Chebyshev complex polynomials that present the fitting results of horizontal, rocking, and coupling impedance functions. Then, a model of the soil–foundation–tank–liquid–baffle system is constructed on the basis of the substructure approach. The present sloshing frequencies, sloshing height, and hydrodynamic shear as well as the moment under rigid/soft soil foundations are compared to the available exact results and the numerical results to prove the validity of the present model. The error of the maximum sloshing height between the present and the numerical solutions is within 5.27%; the solution efficiency of system dynamics from the present model is 40–50 times faster than that from the ADINA model. A detailed parameter analysis of the dynamic characteristics and earthquake responses of the coupling system is presented. The research novelty is that an equivalent analytical model is presented, and it allows for investigating the dynamics of soil-supported multiple cylindrical tanks with a baffle, providing acceptable accuracy and high calculation efficiency.

Numerical simulation of liquid sloshing in a spherical tank by MPS method

Numerical simulation of liquid sloshing in a spherical tank by MPS method

Effect of the pore parameters of the perforated baffle on the control of liquid sloshing

The phenomenon of liquid sloshing inside a tank has a significant negative impact on the safety of the vessel. Installing perforated baffles is considered an effective means of mitigating liquid sloshing. This study investigated the influence of pore parameters on the anti-sloshing effectiveness of baffles. The simulations were performed using STAR-CCM+. In the numerical simulation of the tank sloshing, we have adjusted the factors in the k-ε model to obtain more approximate results compared to the experiments. By changing variables such as the porosity, degree of porosity, and pore distribution of the baffles, the results of the numerical simulations were compared to analyze their performance. Different combinations of porosity and porosity degree parameters have varying effects on sloshing factors such as the wave height, pressure, and rolling moment of the liquid tank. The perforated baffle performed well at restraining the slamming load. The findings also indicate that the effects of porosity are greater than those of the pore distribution. In most cases, an even pore distribution is more effective. These results can provide guidelines for the optimal design of vertical porous baffles.

Experimental Study on Impulse-Induced Liquid Sloshing Modes and Frequencies in Rectangular Tanks

Storage tanks are extensively used containers in various industries for storing diverse liquids. The sloshing of liquid in these containers, often caused by earthquakes, is an emerging issue in the context of damage sustained by tanks. Thus, the seismic resilience of a tank is a critical performance criterion in tank design. Given the complexity of liquid sloshing, the fundamental characteristics of this phenomenon must be examined to gain insights into fundamental sloshing behavior. Liquid sloshing typically involves a combination of fundamental and higher sloshing modes, and the modes and frequencies of liquid sloshing are therefore crucial for assessing this complex behavior. In this study, a shaking table test was employed to analyze the characteristics of liquid sloshing modes. The shapes of the first three sloshing modes under unidirectional excitation were determined and used to validate their symmetry. The findings indicate that the first sloshing mode exerts a more pronounced influence on liquid sloshing during free oscillation induced by unidirectional and horizontal excitation. The modal contribution factor of the first sloshing mode escalates with an increase in the ratio of the liquid level to the length of the tank parallel to the shaking direction, eventually converging toward a constant value.

Toward Virtual Testing of Unmanned Aerial Spraying Systems Operating in Vineyards

In recent times, the objective of reducing the environmental impact of the agricultural industry has led to the mechanization of the sector. One of the consequences of this is the everyday increasing use of Unmanned Aerial Systems (UAS) for different tasks in agriculture, such as spraying operations, mapping, or diagnostics, among others. Aerial spraying presents an inherent problem associated with the drift of small droplets caused by their entrainment in vortical structures such as tip vortices produced at the tip of rotors and wings. This problem is aggravated by other dynamic physical phenomena associated with the actual spray operation, such as liquid sloshing in the tank, GPS inaccuracies, wind gusts, and autopilot corrections, among others. This work focuses on analyzing the impact of nozzle position and liquid sloshing on droplet deposition through numerical modeling. To achieve this, the paper presents a novel six degrees of freedom numerical model of a DJI Matrice 600 equipped with a spray system. The spray is modeled using Lagrangian particles and the liquid sloshing is modeled with an interface-capturing method known as Volume of Fluid (VOF) approach. The model is tested in a spraying operation at a constant velocity of 2 m/s in a virtual vineyard. The maneuver is achieved using a PID controller that drives the angular rates of the rotors. This spraying mission simulator was used to obtain insights into optimal nozzle selection and positioning by quantifying the amount of droplet deposition.

Comparative study of WCSPH, EISPH and explicit incompressible-compressible SPH (EICSPH) for multi-phase flow with high density difference

This study presents three Smoothed Particle Hydrodynamics (SPH) methods capable of handling high-density differences in violent incompressible multiphase flows. The conventional Weakly Compressible SPH (WCSPH) is reformulated into a quasi-Lagrangian framework based on Arbitrary Lagrangian–Eulerian (ALE) context. The Explicit Incompressible SPH (EISPH) method is extended to handle multiphase flows and reformulated in the ALE framework. The Explicit Incompressible-Compressible SPH (EICSPH) method, which can handle both compressible and incompressible phases, is developed by combining these two approaches in a fully explicit algorithm. The proposed methods are validated and compared through four benchmark problems including Rayleigh-Taylor instability, hydrostatic, liquid sloshing and dam break problems. Firstly, the stability and accuracy of interface modeling of the three methods were verified through Rayleigh-Taylor instability with small density differences. In the hydrostatic problem with a large density difference, the results from all three methods exhibit good agreement in the pressure distribution. Particularly, EICSPH demonstrates the faster convergence when compared to WCSPH, with EISPH showing fastest convergence overall. In the transient sloshing problem, all three methods quantitatively converged to the experimental results and exhibited good agreement, although slight pressure noise was observed in WCSPH initially. Finally, in the dam break problem, all three methods successfully simulated sharp interfaces without non-physical voids. The temporal variations of pressure and height were well predicted by all three methods, with EISPH showing better conformity to the water-air interface morphology obtained from other incompressible numerical methods compared to WCSPH and EICSPH. Additionally, the impact of air speed of sound was examined in EICSPH, where while the difference in pressure variation at the probe was minimal, differences were observed in energy dissipation and the progression of the free surface due to the air cushion effect.

Predefined-time sliding mode attitude control for liquid-filled spacecraft with large amplitude sloshing

In the present study, a predefined-time attitude stabilization for liquid-filled spacecraft with large liquid sloshing is investigated under input saturation and external disturbance. First, the large slosh of the liquid is equivalent to the motion pulsating ball model (MPBM), and the dynamic model of the rigid-liquid coupling system is established. Then, liquid sloshing state quantity-related items and external disturbances are combined to form a lumped disturbance. A predefined-time disturbance observer is proposed to accurately reconstruct the lumped disturbance within a predefined-time regardless of the initial estimated state. Based on the proposed predefined-time disturbance observer, a predefined-time sliding mode surface is designed. The predefined-time stability of the proposed observer and controller is proved using the Lyapunov function. Finally, a variable-speed reaching law and exponential reaching law are combined to suppress the chattering caused by sliding mode control. To this end, a new auxiliary function is developed to consider the effects of input saturation. The simulation results show that the proposed controller can effectively stabilize the attitude stability of the liquid-filled spacecraft.

A consistent second order ISPH for free surface flow

The Incompressible Smoothed Particle Hydrodynamics (ISPH) is now a popular numerical method for modelling free surface flows, in particular the breaking waves and violent wave-structures interaction. The ISPH requires the projection approach, leading to solving a pressure Poisson's equation (PPE). Although the accuracy and convergence of the numerical scheme to discretise the Laplacian operator involved in PPE is critical for securing a satisfactory solution of the PPE, the overall performance of the ISPH is also influenced by other key numerical implementations, including (1) estimation of the viscous terms; (2) calculation of the velocity divergence; (3) discretisation of the boundary conditions for the PPE; and (4) evaluation of the pressure gradient. In our previous paper [29], the quadratic semi-analytical finite difference interpolation scheme (QSFDI), which has a leading truncation error at third order derivatives, has been adopted to discretise the Laplacian operator. In this paper, the QSFDI will be adopted, not only for discretising the Laplacian operator, but also for approximating viscous terms, velocity divergence, boundary conditions and pressure gradient. The performance of the newly formulated consistent second order ISPH is assessed by various cases including the oscillating liquid drop, the wave propagation, and the liquid sloshing. The results do not only demonstrate a second order convergence over a limited range of conditions and a higher computational efficiency, i.e., requiring less computational time to achieve the same accuracy, but also show a better mass/energy conservation property and capacity of reproducing a smooth pressure field, than other ISPH models considered in this study.

Study of effect of rotational axis configurations on the slosh dynamics of the ship-mounted tank under different combinations of rotational excitations

Study of effect of rotational axis configurations on the slosh dynamics of the ship-mounted tank under different combinations of rotational excitations

Numerical investigation of liquid sloshing in 2D flexible tanks subjected to complex external loading

Due to the complexity of fluid–structure interactions (FSI), the majority of studies in the literature dealing with the sloshing problem are restricted to rigid tanks. This paper is devoted to a numerical investigation of the liquid sloshing behavior in a flexible tank subjected to external loading. A numerical methodology is proposed, taking into account the FSI problem by coupling two open-source codes: OpenFOAM for the fluid and FEniCS for the solid, using the preCICE library, a free library for fluid–structure interaction. The Arbitrary Lagrangian–Eulerian formulation is used for the two-phase flow system to solve the Navier–Stokes equations in the fluid domain using the finite volume method. Simultaneously, the linear-elastic equation of the structure is solved using the finite element method. An implicit coupling scheme is considered at the fluid–structure interface. The numerical methodology is validated by the results given in literature for harmonic excitation at different frequencies. Subsequently, an analysis of complex external loading, such as Gabor wavelets and earthquake ground motion, is conducted to highlight the significant impact of the wall flexibility on sloshing, as well as the influence of hydrodynamic forces on the structure’s deformation. The proposed coupling methodology is robust and effective, it can be applied to all types of liquids and materials. A dataset of one of the studied cases is given as a supplement to the paper (Kha et al., 2024).

Cooperative-transportation dynamics of two helicopters transporting a rocket booster undergoing planar motions

Helicopters are widely used in the field of material transportation as flying cranes. There have been attempts to utilize helicopters to capture a rocket booster that has been slowed down in the air by a parachute. However, when the rocket booster exceeds the load limit of single helicopter, the cooperative use of two or more helicopters must be considered. The cooperative system becomes coupled, and complicated, as a result of the dynamic effects added by multiple helicopters and cables, as well as the remaining liquid fuel in the rocket booster. This paper establishes a fully-coupled dynamic model of two helicopters transporting a rocket booster, which can describe the coupled effects among the helicopter attitudes, load pendulum, and liquid sloshing. In order to improve the ability to resist external disturbances, and induce minimal attitude oscillations and load pendulum swing during flight, a cooperative controller consisting of a modified model-following controller and a hybrid piecewise smoother is proposed. To quantitatively prove the control performance and robustness, computational simulations were performed comparing the proposed controller with a previous combined controller.

Effects of seismic characteristics and baffle damping on liquid sloshing

The present work concentrates on liquid sloshing in tanks under real seismic excitations with various frequency contents [the ratio of peak ground acceleration (PGA) to peak ground velocity (PGV)] by a finite-difference turbulent model. The turbulence is modeled by the large eddy simulation, and the fluid–structure interaction is resolved by the Virtual Boundary Force method. Thirteen seismic records, covering the low, intermediate and high frequency contents, are adopted to excite nonlinear sloshing waves. Both sloshing wave and hydrodynamic pressure are recorded, and their correlations with the filling level, PGA, PGV and frequency content have been identified. The findings suggest that (1) the sloshing responses are in general positively correlated with the filling level; (2) the sloshing height strongly relates to PGV and frequency content, and the seismic excitation of low frequency and meantime with a larger PGV can trigger more violent sloshing waves than others; and (3) the dynamic pressure along the tank sidewall decreases from the bottom up, which is dominated by PGA at the lower part but the stronger correlation is established with PGV and frequency content at the upper part. Finally, to damp severe sloshing waves, the horizontal, vertical and coupled horizontal and vertical baffles are introduced, and their inhibiting effects are discussed. The present work may guide the design of partially filled storage tanks under seismic excitations.

Study of Inhibitory Effects of Elastic Membranes on Liquid Sloshing in Partially Filled Tank Vehicles

Study of Inhibitory Effects of Elastic Membranes on Liquid Sloshing in Partially Filled Tank Vehicles

Full Dynamic Model for Liquid Sloshing Simulation in Cylindrical Tank Shape

Full Dynamic Model for Liquid Sloshing Simulation in Cylindrical Tank Shape

CFD Analysis of Sloshing in the Fuel Tank of a Heavy Vehicle with Emergency Braking System

Liquid sloshing, which occurs in all accelerating and liquid-carrying vehicles, is of great importance, especially in the automotive and aerospace industries. Large-scale fluid sloshing causes both operational and safety problems in vehicles. In this study, the fuel tank of a heavy vehicle with an emergency braking system is designed in three dimensions, and liquid sloshing in the fuel tank is investigated by CFD analysis meth-od. VOF solution method, k-ԑ turbulence model, and PISO solution algorithm are used in the study. In the analysis of liquid sloshing, it is assumed that the vehicle is traveling at a certain speed, decelerates and stops with emergency braking, and remains station-ary for a while. The braking scenario and boundary conditions are based on test data from a heavy vehicle manufacturer. The designed fuel tank with a capacity of 207.6 li-ters was analyzed at 25%, 50%, and 60% diesel fuel filling levels in 6 different cases with and without anti-slosh baffles. Four virtual sensors were placed on the side wall of the fuel tank in the direction of vehicle movement, and time-dependent pressure changes were analyzed for all cases. In addition, the fuel volume ratio in all cases is visualized and presented for specific time steps. With the use of anti-slosh baffles, the maximum pressure, the rate of pressure increase, and the liquid sloshing were reduced by a factor of 2-3 for different cases. With the design of the fuel tank using anti-slosh baffles, instantaneous interruptions in the fuel system are prevented. Reducing the im-pact pressures on the tank walls is expected to positively affect noise, vibration, and stability problems.

Numerical investigation on the effects of wave suppression baffles in vehicle-integrated water tanks

The danger of liquid sloshing in pump-driven water tanks has significantly increased due to the growing need to integrate a water tank into new energy vehicles. The best approach to reduce the negative effects of liquid sloshing is to add baffles to the integrated water tank. The addition of baffles to integrated water tanks to reduce liquid sloshing is investigated in this study using the discontinuous mesh approach and the coupled level set and volume of fluid (CLSVOF) method. Comparative experiments and simulations are used to confirm the reliability of the method. In this study, the length ratio, distance to initial free surface, and angle of the added baffle are taken into consideration. The free surface height, magnitude velocity, turbulence energy, and flow field are used to assess the impact of the baffle on the suppression of liquid sloshing. The addition of baffles can improve the liquid sloshing phenomenon caused by the pump excitation conditions in the integrated water tank, increase the volume suction of liquid, inhibit the height of the wave and reduce the liquid flow rate in the tank. Also, at the depth where the baffle has the most obvious suppression effect, the deeper the baffle, the lower the height of the free surface in the tank and the lower the average magnitude velocity in the tank cross-section. The baffle reduces the height of the free surface in the tank to 6.39 mm, and the magnitude of maximum average velocity in the tank cross-section is reduced to 0.12 m/s.

Experimental analysis of liquid vertical slosh damping at vacuum and atmospheric pressures

Experimental data are presented for a cantilevered vertically vibrating beam supporting a tank partially filled with liquid, inside a vacuum chamber where the air pressure can be reduced. Results are presented with and without the tank and contained liquid, as well as under two different gas pressures (atmospheric and vacuum). When the liquid is absent from the tank, aerodynamic damping and added mass effects are quantified. When the tank is partially filled with liquid, the damping versus tank amplitude curves indicate differences that are mainly due to aerodynamic effects, with more noticeable effects in the 50% fill case. The results support the observation that at the density ratios presented here, two-phase liquid/ gas modelling may not be needed for the evaluation of net damping due to violent sloshing flows.

Seismic performance improvement of liquid storage tank based on base-isolation and pendulum tuned mass damper

It is necessary to ensure the safety of liquid storage tanks under earthquakes, but the damage probability of the non-damping liquid storage tanks is higher under earthquakes. Based on the damping principle of tuned mass damper (TMD) and the characteristics of the liquid storage tank, a new pendulum TMD (PTMD) system is proposed. Considering the material nonlinearity, the fluid–structure interaction and liquid sloshing characteristics, the three-dimensional numerical calculation models of the non-damping, PTMD, base-isolation (BI) and BI-PTMD liquid storage tanks are established, respectively. The seismic responses of different types of liquid storage tanks under the action of near-field pulse-like earthquakes are investigated, the damping performance of the hybrid control system with the isolation and the PTMD is analyzed, and the influence laws of the mass ratio of PTMD-structure and base-isolation period on the dynamic responses of the liquid storage tanks are discussed. The results show that the BI-PTMD hybrid control system has a significant damping effect on the seismic responses of the liquid storage tank. The damping rate of the base shear is the largest, reaching 86.0%, and the control rate of the PTMD on the displacement of the isolation layer is about 20.0%. The hoop stress, effective stress, liquid pressure and displacement of isolation layer decrease with the increase of the mass ratio of PTMD to structure. With the increase of base-isolation period, the hoop stress, axial compressive stress, effective stress and liquid pressure decrease, and the control effect of PTMD on the liquid storage tank is weakened.