scholarly journals Investigation of Zero Moment Point in a Partially Filled Liquid Vessel Subjected to Roll Motion

2020 ◽  
Vol 10 (11) ◽  
pp. 3992
Author(s):  
Muhammad Usman ◽  
Muhammad Sajid ◽  
Emad Uddin ◽  
Yasar Ayaz
Keyword(s):  
Autonomous Vehicles ◽  
Center Of Mass ◽  
Flow Analysis ◽  
Liquid Interface ◽  
Liquid Region ◽  
Time Step ◽  
Two Phase ◽  
Zero Moment Point ◽  
Zero Moment ◽  
Air Liquid Interface

Liquid-handling robots are designed to dispense sub-microliter quantities of fluids for applications including laboratory tests. When larger amounts of liquids are involved, sloshing must be considered as a parameter affecting stability, which is of significance for autonomous vehicles. The measurement and quantification of slosh in enclosed volumes poses a challenge to researchers who have traditionally resorted to tracking the air–liquid interface for two-phase flow analysis. There is a need for a simpler method to predict rollover in these applications. In this work, a novel solution to address this problem is proposed in the form of the Zero Moment Point (ZMP) of a dynamic liquid region. Computational experiments of a partially filled, two-dimensional liquid vessel were carried out using the Volume of Fluid (VOF) method in a finite volume based open-source computational fluid dynamics solver. The movement of the air–liquid interface was tracked, while the Center of Mass and the resulting Zero Moment Point were determined from the numerical simulations at each time step. The computational model was validated by comparing the wall pressure and movement of the liquid-free surface to experimentally obtained values. It was concluded that for a dynamic liquid domain, the Zero Moment Point can be instrumental in determining the stability of partially filled containers subjected to sloshing.

Computational Evaluation of Stability in Slosh Dynamics of Tank Vehicles Using Zero Moment Point

2019 ◽  
Author(s):  
M. Usman ◽  
M. Sajid
Keyword(s):  
Free Surface ◽  
Center Of Mass ◽  
Three Dimensional ◽  
Computational Effort ◽  
Surface Boundary ◽  
Zero Moment Point ◽  
Liquid Domain ◽  
Computational Evaluation ◽  
Zero Moment ◽  
Tank Vehicles

Abstract Sloshing characterized by inertial waves has an adverse effect on the directional dynamics and safety of partially filled tank vehicles, limiting their stability and controllability during steering, accelerating or braking maneuvers. A mathematical description of the transient fluid slosh in a horizontal cylindrical tank should consider the simultaneous lateral, vertical and roll excitations assuming potential flows and a linearized free-surface boundary condition. While the determination of vehicle stability would require coupling this model to a dynamic roll plane model of a tank vehicle resulting in a computationally expensive analysis. Considering the need for a simpler method to predict roll stability for partially filled tank vehicles, we explore the Zero Moment Point of a liquid domain as a novel solution to this challenge. Numerical investigations are carried out in a three-dimensional partially filled tanks while tracking the movement of the liquid-air interface by employing the volume of fluid method in OpenFOAM. The center of Mass and Zero Moment Point were calculated from the computational results using analytical expressions. The movement of free surface is found to be in good agreement with available literature. The center of mass of the liquid domain was traced as a practical means to quantify the slosh in the tanker. The analyses are performed for different fluid fill heights at varying speeds. The results suggest that the roll stability of tank vehicles can be efficiently analyzed using the zero moment point with significantly lower computational effort.

Incipience of Liquid Entrainment From a Stratified Gas-Liquid Region in Multiple Discharging Branches

2007 ◽  
Vol 130 (1) ◽  
Author(s):  
R. C. Bowden ◽  
I. G. Hassan
Keyword(s):  
Industrial Applications ◽  
Liquid Interface ◽  
Liquid Level ◽  
Analytical Models ◽  
Liquid Region ◽  
Critical Height ◽  
Two Phase ◽  
Curvature Effects ◽  
Liquid Entrainment ◽  
Flow Quality

The onset of liquid entrainment in discharging branches, from a stratified gas-liquid region, has implications in industrial applications where safety is of concern. The onset criterion was characterized by the critical height, the vertical distance from the discharge inlet to the gas-liquid interface, and was shown to be a function of the Froude number. The critical height signified a transition in the discharging flow quality from a single phase gas to a two-phase gas-liquid mixture. The onset of liquid entrainment with multiple discharging branches, and a stratified gas-liquid region, was experimentally investigated using air and water. A test section with a semicircular cross section and three discharging branches at 0deg, 45deg, and 90deg was used. The critical height was recorded using both increasing and decreasing liquid level methods, thereby demonstrating surface tension and wetness effects. A total of eight cases were investigated for single, dual, and triple discharges, with onset occurring in the branch closest to and above the gas-liquid interface. Wall curvature effects were discussed through comparison with previous flat wall studies. Agreement between previously developed analytical models and the decreasing liquid level results was found.

Numerical modeling of liquid sloshing in flexible tank with FSI approach

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Lydia Khouf ◽  
Mustapha Benaouicha ◽  
Abdelghani Seghir ◽  
Sylvain Guillou
Keyword(s):  
Numerical Modeling ◽  
Dynamic Response ◽  
Large Amplitude ◽  
Stokes Equations ◽  
Liquid Interface ◽  
Liquid Sloshing ◽  
Added Value ◽  
Two Phase ◽  
Content Type ◽  
Air Liquid Interface

Purpose The paper aims to present a numerical modeling procedure for the analysis of liquid sloshing in a flexible tank subjected to an external excitation, with taking into account the effects of fluid–structure interaction (FSI). Design/methodology/approach A numerical model based on coupling a two-phase flow solver and an elastic solid solver is developed in OpenFOAM code. The Arbitrary Lagrangian–Eulerian formulation is adopted for the two-phase Navier–Stokes equations in a moving domain. The volume of fluid (VOF) method is applied for the air–liquid interface tracking. The finite volume method is used for the spatial discretization of both the fluid and the structure dynamics equations. The FSI coupling problem is solved by an explicit coupling scheme. The model is validated for linear and nonlinear sloshing cases. Then, it is used to analyze the effects of the liquid sloshing on the dynamic response of the tank and the effects of the tank flexibility on the liquid sloshing. Findings The obtained results show that the flexibility of the tank walls amplifies the amplitude of the sloshing and increases the fluctuation period of the air–liquid interface. Furthermore, it is found that the bending moment acting on the tank walls may be underestimated when rigid walls assumption is adopted as usually done in sloshing tank modeling. Also, tank walls flexibility causes a phase shift in the free surface dynamic response. Originality/value A review of previous studies on liquid sloshing in flexible tanks revealed that FSI effects have not been clearly and comprehensively analyzed for large-amplitude liquid sloshing. Many physical and numerical aspects of this problem still require clarifications and enhancements. The added value of the present work and its originality lie in the investigation of large-amplitude liquid sloshing in flexible tanks by using a staggered coupling approach. This approach is carried out by an original combination of a linear solid solver with a two phase fluid solver in OpenFOAM code. In addition, FSI effects on some response quantities, identified and analyzed herein, have not been found in the previous works.

A Numerical Study of BWR Steam Separator

2002 ◽  
Author(s):  
Haruo Terasaka ◽  
Sensuke Shimizu
Keyword(s):  
Transient Flow ◽  
Numerical Study ◽  
Fluid Model ◽  
Flow Analysis ◽  
Phase Flow ◽  
Step Size ◽  
Time Step ◽  
Two Phase ◽  
Time Step Size ◽  
Steam Separator

An advanced numerical method based on two-fluid model of two-phase flow has been developed to simulate the swirling gas-liquid flow and the phase separation process in a Boiling Water Reactor separator. The goal is to correctly predict the performance of operating steam separator as well as new designs. The solution method present here is an extension of SIMPLEST scheme, a fully implicit scheme for single-phase flow analysis. It is robust and unconditionally stable, therefore enable us to use very large time step size. This feature is suitable for steady and/or slow transient flow analyses. Furthermore, it enhances numerical stability during rapid transient calculations. By employing this method, separator hydrodynamics around swirler were calculated.

A Numerical Simulation of Swirling Two-Phase Flow in BWR Steam-Water Separator and Its Optimization

2003 ◽  
Author(s):  
Haruo Terasaka ◽  
Sensuke Shimizu ◽  
Minoru Kawahara
Keyword(s):  
Transient Flow ◽  
Fluid Model ◽  
Flow Analysis ◽  
Phase Flow ◽  
Step Size ◽  
Time Step ◽  
Two Phase ◽  
Time Step Size ◽  
Fully Implicit ◽  
Water Separator

An advanced numerical method based on the two-fluid model has been developed. The solution method presented here is an extension of the SIMPLEST scheme, a fully implicit scheme for single-phase flow analysis. It is robust and unconditionally stable, and therefore it enables us to use a very large time step size. This feature is suitable for steady and/or slow transient flow analyses. Furthermore, it enhances numerical stability during rapid transient calculations. By using this method, swirling gas-liquid flow in a steam-water separator of Boiling Water Reactors (BWRs) was calculated and the hydrodynamics characteristics were investigated for optimization.

A UNIVERSAL BIPED WALKING GENERATOR FOR COMPLEX ENVIRONMENTS WITH PATTERN FEASIBILITY CHECKING

2011 ◽  
Vol 08 (02) ◽  
pp. 323-357 ◽  
Author(s):  
JINSU LIU ◽  
FENG XUE ◽  
XIAOPING CHEN
Keyword(s):  
Efficient Method ◽  
Dynamic Balance ◽  
Working Time ◽  
Complex Environments ◽  
Time Step ◽  
Biped Walking ◽  
Zero Moment Point ◽  
Point Sampling ◽  
Zero Moment

In this paper, we propose a universal biped walking generator that can plan smooth and flexible walking motions in complex environments, including stairs, slopes, and obstacles. In addition to generating collision-free patterns while keeping the balance of the robot, this generator also checks whether the patterns are achievable for the robot. Aiming at this goal, we introduce a simplified walking method to specify the complete biped motions with the unit of a walking step, instead of a time step of the robot's working time used in usual methods. The zero moment point sampling search is also proposed as an efficient method to determine the walking solution for a feasible footstep plan while simultaneously considering dynamic balance and feasibility. Furthermore, another sampling-based algorithm is proposed to revise unfeasible footstep plans to feasible ones. The feasibility and the efficiency of our proposed approach are demonstrated by experiments on simulated and real Nao robots.

Rapid, efficient and dose-controlled delivery of liquid aerosol to pulmonary cells cultured at the air-liquid interface

Pneumologie ◽  
2011 ◽  
Vol 65 (12) ◽  
Author(s):  
M Selmansberger ◽  
AG Lenz ◽  
M Schmidmeir ◽  
O Eickelberg ◽  
T Stoeger ◽  
...  
Keyword(s):  
Liquid Interface ◽  
Controlled Delivery ◽  
Pulmonary Cells ◽  
Air Liquid Interface ◽  
Cells Cultured

Zwischen Luft und Wasser – Air-Liquid-Interface-Kulturen als In-vitro-Modell des Respirationstrakts

2020 ◽  
Author(s):  
S. Runft ◽  
L. Burigk ◽  
A. Lehmbecker ◽  
K. Schöne ◽  
D. Waschke ◽  
...  
Keyword(s):  
Liquid Interface ◽  
Air Liquid Interface
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