Numerical study on the shear-induced lift force acting on a spherical bubble in aqueous surfactant solutions

2008 ◽  
Vol 20 (4) ◽  
pp. 040704 ◽  
Author(s):  
Masato Fukuta ◽  
Shu Takagi ◽  
Yoichiro Matsumoto
Keyword(s):  
Lift Force ◽  
Numerical Study ◽  
Spherical Bubble ◽  
Surfactant Solutions

Shear-Induced Lift Force on a Single Bubble in Surfactant Solutions

2007 ◽  
Author(s):  
Masato Fukuta ◽  
Shu Takagi ◽  
Yoichiro Matsumoto
Keyword(s):  
Lift Force ◽  
Marangoni Effect ◽  
Surface Concentration ◽  
Bubble Surface ◽  
Single Bubble ◽  
Bubble Motion ◽  
Surfactant Solutions ◽  
Cap Model ◽  
Desorption Rate Constant ◽  
The Asymmetry

In this paper, single bubble motion in surfactant solutions is discussed. We focus on the change of the shear-induced lift force acting on a bubble when the bubble surface is contaminated by surfactant adsorption which leads the Marangoni effect. With the increase of Langmuir number corresponding to the decrease of desorption rate constant of surfactant, the lift force on a spherical bubble decreases from that on a clean bubble to near zero value. This reduction is related significantly to the asymmetry of pressure distribution on surface. Comparing the present result with our previous simulation using the stagnant cap model, the lift force of this study is larger than that of the stagnant cap model. This is because in a shear flow, the surface concentration distributes asymmetrically, and the asymmetry of the surface pressure produced by the shear appears stronger than that of the stagnant cap model.

Numerical Study on Vortex-Induced Motions of Semisubmersibles With Three Columns With Different Sections Types

2019 ◽  
Author(s):  
Chenling Tian ◽  
Longfei Xiao ◽  
Mingyue Liu ◽  
Lijun Yang ◽  
Jing Liu
Keyword(s):  
Wind Turbine ◽  
Lift Force ◽  
Transverse Direction ◽  
Numerical Study ◽  
Offshore Structures ◽  
Detached Eddy Simulation ◽  
Fluid Forces ◽  
Eddy Simulation ◽  
Resonance Behavior ◽  
Induced Motion

Abstract Vortex-induced motion (VIM) phenomenon is a great challenge for design and operation of offshore structures subjected to ocean flow. Semi-submersibles with three columns are often applied to the field of wind turbine, suffering VIM motions probably. In recent years, it is showed that many factors have more or less influence on VIM of platforms. A comparison of circular columns with square columns on VIM characteristics of three-column semisubmersibles is carried out using the detached eddy simulation (DES) method via Star-ccm+ software. This paper analyzes motions in the transverse direction and yaw, as well as fluid forces including drag force and fluctuating lift force. The results show that transverse amplitudes of semisubmersible with three square columns are much lower than those of semisubmersible with three circular columns at all incidences. Besides, the authors conclude that the semisubmersible with three square columns do not experience obvious resonance behavior, which is different from the semisubmersible with three circular columns. Besides, galloping phenomenon occurred at large reduced velocities at 0°-incidence for the semisubmersible with three square columns, which is likely not induced by lift force directly. Meanwhile, in these cases, yaw amplitudes are also larger than the others. This may be due to the galloping behavior, which is just a conjecture.

Scouring Below Pipelines: The Role of Vorticity and Turbulence

2010 ◽  
Author(s):  
Matteo Mattioli ◽  
Alessandro Mancinelli ◽  
Giuseppina Colicchio ◽  
Maurizio Brocchini
Keyword(s):  
Numerical Model ◽  
Lift Force ◽  
Stokes Equations ◽  
Numerical Study ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Offshore Pipeline ◽  
Temporal Averaging ◽  
Force Components

A numerical study on the turbulence and vorticity of local scour underneath an offshore pipeline placed on a non-cohesive sandy seabed and forced by a steady flow current is presented. The numerical model solves the Navier-Stokes equations using an innovative Level Set technique. The model predicts the behavior of the movable sediments through both drift and lift force components. Mean and turbulent flow quantities were extracted by temporal averaging. Results on the distribution and evolution of turbulent kinetic energy and vorticity will be illustrated at the conference.

scholarly journals Numerical Analysis of Lift Generation in a Radial Segmented Gas Seal

2019 ◽  
Author(s):  
Mihai Arghir ◽  
Samia Dahite
Keyword(s):  
Numerical Analysis ◽  
Lift Force ◽  
Previous Analysis ◽  
Numerical Study ◽  
Rotor Speed ◽  
Rotating Shaft ◽  
Annular Ring ◽  
Thrust Bearings ◽  
Unsteady Problem ◽  
Face Seals

Abstract A radial segmented seal is composed of three or six carbon segments that are assembled by a circumferential (garter) spring that presses them against the rotor. Assembled, they take the form of an annular ring. Each segment has several pads that generate a radial lift force depending on the rotor speed. There are many ways of creating effective lift forces. For example, a pocket on the pad creates a lift force because each pad will act as a Rayleigh step bearing. A groove on the rotating shaft will also create a radial lift force on the pad. However, this latter lift force will be unsteady. The aim of the present work is the numerical study of the lift created by a grooved rotor on a pad. Due to the very small operating radial clearances of radial segmented seals (less than 10 μm), the problem can be simplified by analyzing a single pad and a grooved runner. Previous analysis of gas face seals or thrust bearings always considered grooved pads and a smooth runner, even when the runner was grooved. The peculiarity of this study, which is the first of its kind, is considering the unsteady problem of the moving runner grooves. The analysis was performed for a single pad of a radial segmented seal operating with air.

scholarly journals Combination of collocation and factorization methods applied to numerical solutions of bubble-inside drop system dynamics

1999 ◽  
Vol 21 (1) ◽  
pp. 8-24
Author(s):  
Duong Ngoc Hai
Keyword(s):  
System Dynamics ◽  
Pressure Distribution ◽  
Thermal Effect ◽  
Equilibrium Condition ◽  
Lift Force ◽  
Numerical Solutions ◽  
Pressure Waves ◽  
Relative Location ◽  
Spherical Bubble ◽  
Factorization Methods

In the paper the combination of collocation and factorization methods applied to numerical investigation of bubble-inside drop system dynamics is presented. Initially assumed bubble and drop have ellipsoidal forms. The initial relative location of the drop in the bubble is determined by equilibrium condition between drop weight and lift-force due to pressure distribution in gas/vapor. Calculations are implemented for the case of spherical bubble, drop without and with vaporization (thermal effect) and for the experimental case [6] with alumina drop in water in pressure waves.

scholarly journals Numerical Study on the Effect of Non-Sinusoidal Motion on the Energy Extraction Performance of Parallel Foils

2019 ◽  
Vol 9 (3) ◽  
pp. 384
Author(s):  
Yulu Wang ◽  
Fahui Zhu ◽  
Yonghui Xie
Keyword(s):  
Lift Force ◽  
Numerical Study ◽  
Average Power ◽  
Power Coefficient ◽  
Energy Extraction ◽  
Pitching Motion ◽  
Evolution Law ◽  
Sinusoidal Motion ◽  
Oscillation Process ◽  
Extraction Performance

The effect of non-sinusoidal motion which influences the energy extraction performance of foil is considered in this paper. Two oscillation motions, the combined non-sinusoidal plunging and sinusoidal pitching motion, as well as the combined non-sinusoidal pitching and sinusoidal plunging motion, are selected to investigate the oscillation process of two-dimensional parallel foils numerically. The optimal oscillation motion and average power coefficient at different combined motions are gained. The effects of the plunging motion and pitching motion at different oscillation motions are analyzed, and the evolution law of the foil lift force and vortex field are obtained. It is indicated that the non-sinusoidal motion has a significant influence on energy extraction. When the motion is combined (non-sinusoidal plunging and sinusoidal pitching motion), the best extraction performance is gained at Kh = −0.5. The maximal CPm is 0.375 and the maximal η is 0.188. When the motion is combined (non-sinusoidal pitching and sinusoidal plunging motion), the maximal CPm is 0.623 and the maximal η is 0.312 which appear at Kθ = 2. For the same frequency, the more the plunging motion is similar to the sinusoidal motion, the more energy is extracted by foils. While the more the pitching motion approximates to the square wave, the worse the achieved extraction performance is.

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