Bubble Behavior at an Uneven Wall

2016 ◽  
Author(s):  
H. Shmueli ◽  
G. Ziskind ◽  
R. Letan
Keyword(s):  
Bubble Growth ◽  
Three Dimensional ◽  
Grid Method ◽  
Numerical Code ◽  
Interface Tracking ◽  
Bubble Behavior ◽  
Three Dimensional Model ◽  
Surface Geometry ◽  
Initial State ◽  
Channel Orientation

The present study deals with single bubble growth on an uneven wall. A model problem is defined and solved using a three-dimensional numerical simulation. The wall has the shape of a triangular cavity and feature vortices. The equations solved in the present study are based on macro region modelling of the bubble alone and describe its growth from the initial state to detachment from the surface and consequent motion. The model includes a simultaneous solution of conservation equations for the liquid and gaseous phases, in conjunction with three-dimensional interface tracking. The latter is achieved using the level-set method. The numerical modeling includes the multi-grid method. The complete three-dimensional model is discretized using an original in-house numerical code realized in MATLAB. Different cases of bubble growth on the triangular cavity walls are investigated. The main conclusion from the calculations is that the bubble shape and its growth rate strongly depend on its location and on the channel orientation. New features, not possible for flat walls and special for this case, are revealed and discussed. It is demonstrated that under certain conditions, the bubble is obstructed by the surface geometry. It is also shown how a growing bubble affects the flow field inside a cavity, interacting with the vortex structure.

scholarly journals ABOUT WAVELET-BASED MULTIGRID NUMERICAL METHOD OF STRUCTURAL ANALYSIS WITH THE USE OF DISCRETE HAAR BASIS

2018 ◽  
Vol 14 (3) ◽  
pp. 83-102
Author(s):  
Marina L. Mozgaleva ◽  
Pavel A. Akimov ◽  
Taymuraz B. Kaytukov
Keyword(s):  
Structural Analysis ◽  
Three Dimensional ◽  
Grid Method ◽  
Discrete Analogue ◽  
Algebraic Equations ◽  
Initial State ◽  
Haar Basis ◽  
Linear Algebraic Equations ◽  
Gauss Method ◽  
Original Grid

he distinctive paper is devoted to so-called multigrid (particularly two-grid) method of structural analysis based on discrete Haar basis (one-dimensional, two-dimensional and three-dimensional problems are under consideration). Approximations of the mesh functions in discrete Haar bases of zero and first levels are described (the mesh function is represented as the sum in which one term is its approximation of the first level, and the second term is so-called complement (up to the initial state) on the grid of the first level). Special projectors are constructed for the spaces of vector functions of the original grid to the space of their approximation on the first-level grid and its complement (the refinement component) to the initial state. Basic scheme of the two-grid method is presented. This method allows solution of boundary problems of structural mechanics with the use of matrix operators of significantly smaller dimension. It should be noted that discrete analogue of the initial operator equation is a system of linear algebraic equations which is constructed with the use of finite element method or finite difference method. Block Gauss method can be used for direct solution.

Investigation of intelligent reversible diaphragm using shape memory polymers

2017 ◽  
Vol 29 (7) ◽  
pp. 1500-1509 ◽  
Author(s):  
Ran Tao ◽  
Qing-Sheng Yang ◽  
Xia Liu ◽  
Xiao-Qiao He ◽  
Kim-Meow Liew
Keyword(s):  
Shape Memory ◽  
Strain Energy ◽  
Structural Parameters ◽  
Shape Memory Polymer ◽  
Three Dimensional ◽  
Nonlinear Finite Element Method ◽  
Three Dimensional Model ◽  
Initial State ◽  
Whole Process ◽  
Propellant Tank

This article describes design and analysis of a novel reversible diaphragm using shape memory polymer. The reversible diaphragm could be applied to space engineering, such as propellant tank of rocket. The shape memory polymer diaphragm can automatically recover to the initial state after the overturning deformation and thus can be used repeatedly. A three-dimensional model is established to study the overturning and recovery behavior of the shape memory polymer diaphragm.The nonlinear finite element method based on the thermodynamic constitutive equations of shape memory polymer is used to obtain pressure -displacement relations and strain energy variation of SMP diaphragm with approximately hemispherical shape in the whole process of the overturning deformation. The influence of structural parameters and temperature on the overturning and recover behavior is discussed.

Numerical Investigation of the Unsteady Flow at High Reynolds Number Over a Marine Riser With Helical Strakes

2006 ◽  
Author(s):  
Antonio Pinto ◽  
Riccardo Broglia ◽  
Andrea Di Mascio ◽  
Emilio F. Campana ◽  
Pierpaolo Rocco
Keyword(s):  
Fluid Dynamics ◽  
Unsteady Flow ◽  
Numerical Investigation ◽  
Three Dimensional ◽  
Numerical Code ◽  
Three Dimensional Model ◽  
Analysis Phase ◽  
Helical Strakes ◽  
Advanced Analysis ◽  
High Reynolds

Prediction of Vortex-Induced Vibrations (VIV) is one of the main topics in the design of deepwater risers. The understanding and modelling of the complex fluid-structure interaction requires advanced analysis techniques coupling, in a correct manner, both structural and fluid dynamics aspects. This study aims to develop, optimise and calibrate a numerical code to provide reliable results within a reasonable analysis timeframe and without, or very limited, need of experimental verification. For this purpose, the unsteady Reynolds Average Navier-Stokes (RANS) code χnavis is applied to solve a typical riser VIV problem and compute the three-dimensional riser-fluid dynamics interaction. During a preliminary analysis phase, the two-dimensional (2-D) flow past (i) a bare circular cylinder and (ii) a straked riser at high Reynolds numbers is simulated (different incidences flow/strake vanes are analysed). Numerical results are validated and calibrated against published test data. The core analysis phase is then focused on the numerical investigation of the unsteady flow over a three-dimensional (3-D) helical strake. In this phase, the three-dimensional flow field, turbulent structures and response frequency patterns are analysed. Spectral analysis of data is performed to identify carrier frequencies deemed to be critical due to the induced vibration of the whole structure, and helical strakes efficiency in reducing the riser vibrations is also addressed. Finally, comparison between numerical and experimental results shows that the complexity of a three-dimensional model is indeed compensated by a significantly improved accuracy of the obtained results.

Three-Dimensional Simulation of Vapour Bubble Growth in Superheated Water Due to the Convective Action by an Interface Tracking Method

2021 ◽  
Author(s):  
Syed Sharif ◽  
Mark Ho ◽  
Victoria Timchenko ◽  
Guan Yeoh
Keyword(s):  
Heat Transfer ◽  
Surface Tension ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Bubble Growth ◽  
Three Dimensional ◽  
Interface Tracking ◽  
Superheated Water ◽  
Vapour Bubble ◽  
Tracking Method

Abstract In this paper, the growth of a rising vapour bubble in superheated water was numerically studied using an advanced interface tracking method, called the InterSection Marker (ISM) method. The ISM method is a hybrid Lagrangian-Eulerian Front Tracking algorithm that can model an arbitrary Three-Dimensional (3D) surface within an array of cubic control-volumes. The ISM method has cell-by-cell remeshing capability that is volume conservative, maintains surface continuity and is suited for tracking interface deformation in multiphase flow simulations. This method was previously used in adiabatic bubble rise simulation with no heat and mass transfers to or from the bubble were considered. This present work will extend the ISM method's application to simulate vapour bubble growth in superheated water with the inclusion of additional physics, such as the convective heat transfer mechanism and the phase change. Coupled with an in-house variable-density and variable-viscosity single-fluid flow solver, the method was used to simulate vapour bubble growth due to the convective action. The forces such as the surface tension and the buoyancy were included in the momentum equation. The source terms for the mass transfer were also modelled in the CFD governing equations to simulate the growth. Bubble properties such as size, shape, velocity, drag coefficient, and convective heat transfer coefficient were predicted. Effects of surface tension and temperature on the bubble characteristic were also discussed. Obtained numerical results were compared against the analytical and past works and found to be in good agreement.

Research of Wind Shear Dynamic Characteristics of Wind Wheels

2014 ◽  
Vol 1070-1072 ◽  
pp. 1888-1892
Author(s):  
Xiao Ming Chen ◽  
Shun Kang ◽  
Wei Zuo
Keyword(s):  
Wind Turbine ◽  
Wind Shear ◽  
Aerodynamic Characteristic ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Grid Method ◽  
Three Dimensional Model ◽  
Horizontal Axis Wind Turbine ◽  
Calculation Results ◽  
Object Of Study

In order to accurately analysis the aerodynamic characteristic variations of wind turbines under shear, the influence of axial and shear on the aerodynamic characteristic of a horizontal-axis wind turbine is simulated in this paper by using a sliding grid method based on FlowVision. By using the TJÆREBORG wind turbine as the object of study, a three-dimensional model of a uniform wind flow can be created. The CFD calculation results, the experimental results and the Bladed results can be used to confirm the reliability of the model. In order to investigate the effect of wind shear with regard to three-dimensional unsteady flow characteristics and a three-dimensional flow field in a wind turbine impeller, an analysis of wheel wind speed of 11m/s and an investigation of the influence of wind shear on turbine performance are carried out.

A Three-Dimensional Computer Model for Simulation of Light-Trapping Effects in Porous Silicon

1999 ◽  
Vol 579 ◽  
Author(s):  
Peter T. Charbel ◽  
Jim P. Zheng
Keyword(s):  
Porous Silicon ◽  
Light Trapping ◽  
Three Dimensional ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Acceptance Angle ◽  
Surface Geometry ◽  
General Shape ◽  
Experimental Values ◽  
Trapping Effects

ABSTRACTIt has been demonstrated that porous silicon can be used to enhance the sensitivity, spectral bandwidth, and light acceptance angle of photodiodes. In an attempt to better understand light trapping effects in porous silicon, a three-dimensional model was used to approximate the surface geometry of porous silicon. It was found that the main contributing factor to the observed high efficiencies is the shape of the pores. The general shape resembles cylindrical shaped sections, whose radii are in the micron range. The results of the computer simulation were compared to actual experimental results where porous silicon was tested under variable conditions of lighting and porosity. The comparison shows that the simulation gives a good approximation of the behavior of porous silicon. Although the simulation does not perfectly match experimental values, it does provide the insight that the surface geometry of porous silicon is the main contributing factor to its efficiency in trapping light.

Three-Dimensional Calculation of Bubble Growth and Drop Ejection in a Bubble Jet Printer

1992 ◽  
Vol 114 (4) ◽  
pp. 638-641 ◽  
Author(s):  
A. Asai
Keyword(s):  
Experimental Data ◽  
Surface Tension ◽  
Stokes Equation ◽  
Bubble Growth ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Bubble Behavior ◽  
Navier Stokes Equation ◽  
Bubble Pressure ◽  
First Time

The three-dimensional Navier-Stokes equation for the motion of ink both inside and outside the nozzle of a bubble jet printer is numerically solved, for the first time, to predict the bubble behavior and the drop ejection. The results of calculation for three types of ink agreed well with experimental data. The effect of initial bubble pressure, viscosity and surface tension on the volume and the velocity of the drop is numerically investigated. The three-dimensional calculation is very useful to the design of bubble jet printers because it saves a lot of time and cost to make and evaluate prototypes.

scholarly journals Assimilation of stratospheric ozone in the chemical transport model STRATAQ

2004 ◽  
Vol 22 (8) ◽  
pp. 2669-2678 ◽  
Author(s):  
B. Grassi ◽  
G. Redaelli ◽  
G. Visconti
Keyword(s):  
Total Ozone ◽  
Transport Model ◽  
Stratospheric Ozone ◽  
Three Dimensional ◽  
Chemical Transport ◽  
Numerical Code ◽  
Chemical Transport Model ◽  
Three Dimensional Model ◽  
Simultaneous Evaluation ◽  
Analysis Errors

Abstract. We describe a sequential assimilation approach useful for assimilating tracer measurements into a three-dimensional chemical transport model (CTM) of the stratosphere. The numerical code, developed largely according to Kha00, uses parameterizations and simplifications allowing assimilation of sparse observations and the simultaneous evaluation of analysis errors, with reasonable computational requirements. Assimilation parameters are set by using χ2 and OmF (Observation minus Forecast) statistics. The CTM used here is a high resolution three-dimensional model. It includes a detailed chemical package and is driven by UKMO (United Kingdom Meteorological Office) analyses. We illustrate the method using assimilation of Upper Atmosphere Research Satellite/Microwave Limb Sounder (UARS/MLS) ozone observations for three weeks during the 1996 antarctic spring. The comparison of results from the simulations with TOMS (Total Ozone Mapping Spectrometer) measurements shows improved total ozone fields due to assimilation of MLS observations. Moreover, the assimilation gives indications on a possible model weakness in reproducing polar ozone values during springtime.

Numerical Modelling of Fluid Structure Interaction in Blood Vessels

2005 ◽  
Author(s):  
Ian Owens Pericevic ◽  
Moji Moatamedi ◽  
M hamed Souli
Keyword(s):  
Pressure Pulse ◽  
Physiological State ◽  
Fluid Structure Interaction ◽  
Three Dimensional ◽  
Theoretical Description ◽  
Numerical Code ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Fluid Structure ◽  
Structure Interaction

This paper examines the capabilities offered by the fluid structure interaction (FSI) algorithms in LS-DYNA for solving problems in vascular biomechanics. In this work a case was examined in which the onset of a pressure pulse was simulated at the entrance of a straight segment of artery. The resulting dynamic response in the form of a propagating pulse wave through the vessel wall was analyzed and compared to both previous numerical results and theory. The results from the three dimensional model compared well to the theoretical description of an idealized thin-walled artery. Results were further compared to those obtained from similar research. The numerical methodologies applied in the three dimensional model were used in the development of an experiment providing a realistic physical model of a carotid artery in its physiological state. The experiment is to be used for further validation of the numerical code.

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