scholarly journals Dynamic Heeling Moment Due to Liquid Sloshing in a Rectangular Tank of Different Dimensions and Elevation in Ship’S Hull / Dynamiczny Moment Przechylający Od Swobodnych Powierzchni Cieczy W Prostokątnym Zbiorniku Okrętowym O Różnych Wymiarach I Lokalizacji Pionowej

2012 ◽  
Vol 21 (1) ◽  
pp. 51-62
Author(s):  
Przemysław Krata ◽  
Jacek Jachowski
Keyword(s):  
Numerical Simulations ◽  
Liquid Sloshing ◽  
Liquid Motion ◽  
Dynamic Approach ◽  
Rectangular Tank ◽  
Different Dimensions ◽  
Sloshing Phenomenon ◽  
The Stability ◽  
Heeling Moment

Abstract Liquid sloshing phenomenon taking place in partly filled ships’ tanks directly affects the stability of a vessel and her safety on seaway, however, only static calculations are carried out onboard ships nowadays. The presented investigation is focused on dynamic approach towards liquid motion onboard ships. The set of numerical simulations of liquid sloshing taking place in moving tanks is carried out in terms of tank’s dimensions and its elevation within ship’s hull. A number of characteristics of the heeling moment due to liquid sloshing is obtained and analyzed.

scholarly journals Ship’S Rolling Amplitude as a Significant Factor Influencing Liquid Sloshing in Partly Filled Tanks / Amplituda Kołysań Statku Jako Istotny Parametr W Badaniach Zjawiska Sloshingu W Niepełnych Zbiornikach Okrętowych

2012 ◽  
Vol 21 (1) ◽  
pp. 63-76
Author(s):  
Przemysław Krata ◽  
Wojciech Wawrzyński
Keyword(s):  
Numerical Simulations ◽  
Liquid Sloshing ◽  
Liquid Motion ◽  
Dynamic Approach ◽  
Non Linear ◽  
Heeling Moment

Abstract The study considers ship’s rolling amplitude as one of the key parameters influencing liquid sloshing in partly filled tanks during sea voyage. This issue is strictly related to the safety of navigation matters and belongs to the group of non-linear hydrodynamic phenomena. The presented investigation is focused on the estimation of typical and extreme rolling amplitude of a vessel in terms of dynamic approach towards liquid motion onboard ships. The number of exemplary numerical simulations of liquid sloshing taking place in moving tanks is carried out and the heeling moment due to liquid sloshing is obtained.

Study of Hydrostatic Pump Created Under Liquid Sloshing in a Rectangular Tank Subjected to External Excitation

2016 ◽  
Vol 08 (01) ◽  
pp. 1650004 ◽  
Author(s):  
Abdallah Bouabidi ◽  
Zied Driss ◽  
Mohamed Salah Abid
Keyword(s):  
Numerical Simulation ◽  
Excitation Frequency ◽  
Liquid Sloshing ◽  
Experimental Results ◽  
Experimental Setup ◽  
Liquid Motion ◽  
External Excitation ◽  
Sinusoidal Movement ◽  
Rectangular Tank ◽  
External Excitation Frequency

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.

scholarly journals EXPERIMENTAL STUDY OF LIQUID SLOSHING FORCE CHARACTERISTICS IN RECTANGULAR TANK OF SPRAYER UNDER HARMONIC EXCITATION

2020 ◽  
pp. 125-132
Author(s):  
Jizhou Zheng ◽  
Xiang Han ◽  
Haoran Guo ◽  
Jialin Hou ◽  
Xinyu Xue
Keyword(s):  
Passive Control ◽  
Practical Method ◽  
Excitation Amplitude ◽  
Harmonic Excitation ◽  
Liquid Sloshing ◽  
Factors Affecting ◽  
Rectangular Tank ◽  
The Stability ◽  
Violent Sloshing ◽  
Force Characteristics

The stability of the boom system of sprayers is easily affected by the liquid sloshing force and the uniformity of droplet deposition deteriorates. Therefore, the liquid sloshing forces in the rectangular tank were measured through experiments. Three main factors affecting the sloshing forces were examined. Experimental results reveal that the sloshing forces measured fit well with the theoretical curve and the maximum sloshing force is independent of the excitation amplitude for a violent sloshing. Based on these characteristics, a practical method was proposed which can approximately calculate the maximum sloshing force based on the linear model, and can be used for the sprayer chassis design and active and passive control of boom attitude.

scholarly journals Fast-Scale Instability and Stabilization by Adaptive Slope Compensation of a PV-Fed Differential Boost Inverter

2021 ◽  
Vol 11 (5) ◽  
pp. 2106
Author(s):  
Abdelali El Aroudi ◽  
Mohamed Debbat ◽  
Mohammed Al-Numay ◽  
Abdelmajid Abouloiafa
Keyword(s):  
Numerical Simulations ◽  
Full Range ◽  
Weather Conditions ◽  
Current Loop ◽  
Point Tracking ◽  
Bifurcation Phenomena ◽  
Slope Compensation ◽  
Power Point ◽  
The Stability ◽  
Detailed Circuit

Numerical simulations reveal that a single-stage differential boost AC module supplied from a PV module under an Maximum Power Point Tracking (MPPT) control at the input DC port and with current synchronization at the AC grid port might exhibit bifurcation phenomena under some weather conditions leading to subharmonic oscillation at the fast-switching scale. This paper will use discrete-time approach to characterize such behavior and to identify the onset of fast-scale instability. Slope compensation is used in the inner current loop to improve the stability of the system. The compensation slope values needed to guarantee stability for the full range of operating duty cycle and leading to an optimal deadbeat response are determined. The validity of the followed procedures is finally validated by a numerical simulations performed on a detailed circuit-level switched model of the AC module.

scholarly journals Earth-size planet formation in the habitable zone of circumbinary stars

2020 ◽  
Vol 494 (1) ◽  
pp. 1045-1057 ◽  
Author(s):  
G O Barbosa ◽  
O C Winter ◽  
A Amarante ◽  
A Izidoro ◽  
R C Domingos ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Planet Formation ◽  
Terrestrial Planet ◽  
Close Binary ◽  
Habitable Zone ◽  
Density Profiles ◽  
Habitable Planets ◽  
Habitable Zones ◽  
Test Particles ◽  
The Stability

ABSTRACT This work investigates the possibility of close binary (CB) star systems having Earth-size planets within their habitable zones (HZs). First, we selected all known CB systems with confirmed planets (totaling 22 systems) to calculate the boundaries of their respective HZs. However, only eight systems had all the data necessary for the computation of HZ. Then, we numerically explored the stability within HZs for each one of the eight systems using test particles. From the results, we selected five systems that have stable regions inside HZs, namely Kepler-34,35,38,413, and 453. For these five cases of systems with stable regions in HZ, we perform a series of numerical simulations for planet formation considering discs composed of planetary embryos and planetesimals, with two distinct density profiles, in addition to the stars and host planets of each system. We found that in the case of the Kepler-34 and 453 systems, no Earth-size planet is formed within HZs. Although planets with Earth-like masses were formed in Kepler-453, they were outside HZ. In contrast, for the Kepler-35 and 38 systems, the results showed that potentially habitable planets are formed in all simulations. In the case of the Kepler-413system, in just one simulation, a terrestrial planet was formed within HZ.

Mathematical Model Establishment and Analysis on the Pipe Deformation under External Pressure with the Ovality

2013 ◽  
Vol 760-762 ◽  
pp. 2263-2266
Author(s):  
Kang Yong ◽  
Wei Chen
Keyword(s):  
Mathematical Model ◽  
Theoretical Analysis ◽  
Yield Strength ◽  
Residual Stresses ◽  
Numerical Simulations ◽  
Significant Influence ◽  
External Pressure ◽  
Pipe Diameter ◽  
Axial Loads ◽  
The Stability

Beside the residual stresses and axial loads, other factors of pipe like ovality, moment could also bring a significant influence on pipe deformation under external pressure. The Standard of API-5C3 has discussed the influences of deformation caused by yield strength of pipe, pipe diameter and pipe thickness, but the factor of ovality degree is not included. Experiments and numerical simulations show that with the increasing of pipe ovality degree, the anti-deformation capability under external pressure will become lower, and ovality affecting the stability of pipe shape under external pressure is significant. So it could be a path to find out the mechanics relationship between ovality and pipe deformation under external pressure by the methods of numerical simulations and theoretical analysis.

A Different Method to Evaluate the Intact Stability of Floating Structures

1983 ◽  
Vol 20 (01) ◽  
pp. 21-25
Author(s):  
Abobakr M Radwan
Keyword(s):  
Mathematical Formulation ◽  
Variable Cross Section ◽  
Regulatory Body ◽  
Variable Cross ◽  
Buoyant Force ◽  
Floating Structures ◽  
Intact Stability ◽  
Correct Location ◽  
The Stability ◽  
Heeling Moment

A mathematical formulation of a computer-based method to evaluate the intact stability of floating structures is presented. The technique depends on describing the surface of the structure in terms of many small finite elements, which allows the analysis of complicated hull geometry, determining the hydrostatic pressure on each element for a known heel angle, and integrating the pressure forces to find the magnitude, direction, and line of action of the buoyant force. This will result in the correct location of the metacenter for small, as well as large, angles of heel. For structures of variable cross section, the position of the heeled vessel in equilibrium is defined such that the weight is balanced by the buoyant force, and only a pure righting moment associated with the heeling angle is evaluated. Formulation for the wind heeling moment is also presented. Assessment of the stability of the vessel is made from the righting and heeling moment curves in light of regulatory body rules.

Model Test Techniques Developed to Investigate the Wind Heeling Characteristics of Sailing Vessels and Their Response to Gusts

1991 ◽  
Author(s):  
Barry Deakin
Keyword(s):  
Wind Tunnel ◽  
Model Test ◽  
Wind Tunnels ◽  
Stability Assessment ◽  
Tunnel Floor ◽  
The Stability ◽  
Scaled Models ◽  
Scale Data ◽  
Heeling Moment ◽  
Gust Response

During the development of new stability regulations for the U.K. Department of Transport, doubt was cast over many of the assumptions made when assessing the stability of sailing vessels. In order to investigate the traditional methods a programme of work was undertaken including wind tunnel tests and full scale data acquisition. The work resulted in a much improved understanding of the behaviour of sailing vessels and indeed indicated that the conventional methods of stability assessment are invalid, the rules now applied in the U.K. being very different to those in use elsewhere. The paper concentrates on the model test techniques which were developed specifically for this project but which will have implications to other vessel types. The tests were of two kinds: measurement of the wind forces and moments on a sailing vessel; and investigation of the response of sailing vessels to gusts of wind. For the force and moment measurements models were mounted in a tank of water on a six component balance and tested in a large boundary layer wind tunnel. Previous tests in wind tunnels have always concentrated on performance and the heeling moments have not normally been measured correctly. As the measurements of heeling moment at a range of heel angles was of prime importance a new balance and mounting system was developed which enabled the above water part of the vessel to be modelled correctly, the underwater part to be unaffected by the wind, and the interface to be correctly represented without interference. Various effects were investigated including rig type, sheeting, heading, heel angle and wind gradient. The gust response tests were conducted with Froude scaled models floating in a pond set in the wind tunnel floor. A mechanism was installed in the tunnel which enabled gusts of various characteristics to be generated, and the roll response of the models was measured with a gyroscope. These tests provided information on the effects of inertia, damping, rolling and the characteristics of the gust. Sample results are presented to illustrate the uses to which these techniques have been put.

Finite-amplitude internal wavepacket dispersion and breaking

2001 ◽  
Vol 429 ◽  
pp. 343-380 ◽  
Author(s):  
BRUCE R. SUTHERLAND
Keyword(s):  
Numerical Simulations ◽  
Internal Waves ◽  
Large Amplitude ◽  
Finite Amplitude ◽  
Critical Amplitude ◽  
Fully Nonlinear ◽  
Weakly Nonlinear ◽  
The Stability ◽  
The Waves ◽  
Horizontal Wavelength

The evolution and stability of two-dimensional, large-amplitude, non-hydrostatic internal wavepackets are examined analytically and by numerical simulations. The weakly nonlinear dispersion relation for horizontally periodic, vertically compact internal waves is derived and the results are applied to assess the stability of weakly nonlinear wavepackets to vertical modulations. In terms of Θ, the angle that lines of constant phase make with the vertical, the wavepackets are predicted to be unstable if [mid ]Θ[mid ] < Θc, where Θc = cos−1 (2/3)1/2 ≃ 35.3° is the angle corresponding to internal waves with the fastest vertical group velocity. Fully nonlinear numerical simulations of finite-amplitude wavepackets confirm this prediction: the amplitude of wavepackets with [mid ]Θ[mid ] > Θc decreases over time; the amplitude of wavepackets with [mid ]Θ[mid ] < Θc increases initially, but then decreases as the wavepacket subdivides into a wave train, following the well-known Fermi–Pasta–Ulam recurrence phenomenon.If the initial wavepacket is of sufficiently large amplitude, it becomes unstable in the sense that eventually it convectively overturns. Two new analytic conditions for the stability of quasi-plane large-amplitude internal waves are proposed. These are qualitatively and quantitatively different from the parametric instability of plane periodic internal waves. The ‘breaking condition’ requires not only that the wave is statically unstable but that the convective instability growth rate is greater than the frequency of the waves. The critical amplitude for breaking to occur is found to be ACV = cot Θ (1 + cos2 Θ)/2π, where ACV is the ratio of the maximum vertical displacement of the wave to its horizontal wavelength. A second instability condition proposes that a statically stable wavepacket may evolve so that it becomes convectively unstable due to resonant interactions between the waves and the wave-induced mean flow. This hypothesis is based on the assumption that the resonant long wave–short wave interaction, which Grimshaw (1977) has shown amplifies the waves linearly in time, continues to amplify the waves in the fully nonlinear regime. Using linear theory estimates, the critical amplitude for instability is ASA = sin 2Θ/(8π2)1/2. The results of numerical simulations of horizontally periodic, vertically compact wavepackets show excellent agreement with this latter stability condition. However, for wavepackets with horizontal extent comparable with the horizontal wavelength, the wavepacket is found to be stable at larger amplitudes than predicted if Θ [lsim ] 45°. It is proposed that these results may explain why internal waves generated by turbulence in laboratory experiments are often observed to be excited within a narrow frequency band corresponding to Θ less than approximately 45°.

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