scholarly journals Relaxation and breakup of a cylindrical liquid column

1970 ◽  
Vol 39 (2) ◽  
pp. 57-64 ◽  
Author(s):  
Mohammad Ali ◽  
Akira Umemura
Keyword(s):  
Surface Tension ◽  
Stokes Equations ◽  
Capillary Wave ◽  
Three Dimensional ◽  
Surface Tension Force ◽  
Surface Force ◽  
Computer Code ◽  
Vof Method ◽  
Liquid Column ◽  
Navier Stokes

Instability of capillary wave and breakup of a square cylindrical liquid column during its relaxation have been investigated numerically by simulating three-dimensional Navier-Stokes equations. For this investigation a computer code based on volume-of-fluid (VOF) method has been developed and validated with published experimental results. The result shows that the agreement of numerical simulation is quite well with the experimental data. The code is then used to study the capillary wave and breakup phenomena of the liquid column. The investigation shows the underlying physics during relaxation of the square cylindrical liquid column, illustrates the formation and propagation of capillary wave, and breakup processes. The breakup behavior for the present configuration of the liquid column shows some significant differences from those predicted by conventional jet atomization theories. The formation of capillary wave is initiated by the surface tension on the sharp edge of the square end of the cylinder and the propagation of the wave occurs due to the effect of surface tension force on the motion of the fluid. The propagation of capillary wave to the end of liquid column causes a disturbance in the system and makes the waves unstable which initiates the breakup of the liquid column. The characteristics of the capillary wave show that the amplitude of the swell grows faster than the neck of the wave and that of the tip wave grows much faster than the other waves. The velocity of the liquid particle is dominated by the pressure in the liquid column. Keywords: Instability; Continuum surface force; Liquid disintegration; Capillary wave; Surface tension; VOF method doi:10.3329/jme.v39i2.1847 Journal of Mechanical Engineering, Vol. ME39, No. 2, Dec. 2008 57-64

Numerical Study on Impingement of a Droplet upon a Liquid Film

2010 ◽  
Vol 44-47 ◽  
pp. 2499-2503
Author(s):  
Hong Liu ◽  
Mao Zhao Xie ◽  
Su Chun Wang ◽  
Ming Jia
Keyword(s):  
Surface Tension ◽  
Liquid Film ◽  
Stokes Equations ◽  
Numerical Study ◽  
Surface Tension Force ◽  
Surface Force ◽  
Navier Stokes ◽  
Initial Kinetic Energy ◽  
Droplet Impingement ◽  
Fine Grid

This paper reports progress in the numerical simulations of a droplet impingement upon the wall film of the same liquid. The full Navier-Stokes equations are solved in axisymmetric formulation. The surface tension force is modeled by a continuum surface force (CSF) model. An adapting local refinement technique is used to provide the fine grid coupled by the volume-of fluid (VOF) method for tracking the interface between the gas and the droplet and liquid film. Results indicate that the motion behavior of droplet impingement upon the liquid film is dominantly influenced by the initial kinetic energy and the thickness of the film as well as the surface tension and the liquid viscosity.

Experimental and Numerical Analysis of Compressor Inlet Volutes

1997 ◽  
Author(s):  
V. Michelassi ◽  
M. Giachi
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Computer Code ◽  
Navier Stokes ◽  
Complex Flow ◽  
Flow Distortion ◽  
Navier Stokes Equations ◽  
Flow Angle ◽  
Compressor Impeller ◽  
Compressor Inlet

A typical compressor inlet volute is studied by using both experimental and numerical approaches. The highly distorted and complex flow pattern is measured in two typical configurations. Measurements include velocity, flow angle, Mach number and losses. The same geometries are analyzed by using a computer code which solves the three-dimensional Navier-Stokes equations. Turbulence effects are modeled by a two-equation turbulence model. The set of measurements shows the flow distortion induced by the volute, and also highlights how this distortion can be controlled or largely reduced by small modifications to the geometry. The computational results indicate an overall good agreement with the measurements and allow reproducing the changes in the pattern induced by the changes in volute geometry. Both the measurements and computations prove the importance of the optimal design of this component which controls the uniformity of the flow approaching the compressor impeller.

Pinch-Off Mechanism of a Free Elongated Liquid Ligament

2005 ◽  
Author(s):  
Albert Y. Tong ◽  
Zhaoyuan Wang
Keyword(s):  
Relaxation Process ◽  
Stokes Equations ◽  
Surface Tension Force ◽  
Surface Force ◽  
Relaxation Mechanism ◽  
Vital Role ◽  
Navier Stokes ◽  
Relaxation Dynamics ◽  
Navier Stokes Equations ◽  
Determining Factor

The time-dependent relaxation dynamics of a moderately elongated liquid ligament has been studied numerically. The Navier-Stokes equations are solved using a finite-volume formulation with a two-step projection method on a fixed grid. The free surface of the liquid ligament is tracked by a coupled level set and volume-of-fluid (CLSVOF) method with the surface tension force determined by the continuum surface force (CSF) model. The relaxation process of a free elongated liquid ligament has been simulated and the numerical results are in agreement with findings reported in the literature. The end-pinching mechanism of the breakup process has been thoroughly examined. The determining factor for reopening of a pinching neck has been identified. The effects of several parameters on the relaxation mechanism have also been examined. It has been found that the initial end shape of the ligament and the Ohnesorge number play a vital role in the overall relaxation process.

A Level Set Method for Simulation of Coalescence of Droplets

2005 ◽  
Author(s):  
A. Salih ◽  
S. Ghosh Moulic
Keyword(s):  
Surface Tension ◽  
Level Set Method ◽  
Level Set ◽  
Stokes Equations ◽  
Surface Tension Force ◽  
Tension Force ◽  
Staggered Grid ◽  
Navier Stokes ◽  
Level Set Function ◽  
Set Function

In the present paper, we discuss a numerical method based on the level set algorithm to simulate two-phase fluid flow systems. Surface tension force at the fluid interface is implemented through the CSF model of Brackbill et al. [1]. The incompressible Navier-Stokes equations were solved on a staggered grid using an explicit projection method. A fifth-order WENO [2] scheme was used for advancing the level set function. We improved the implementation of WENO scheme by staggering the level set function. The Navier-Stokes part of the code was validated by computing the standard lid-driven cavity flow and the free surface part of the code was validated by advecting the interface in a prescribed velocity field. The Young-Laplace law for a static drop has been verified to validate the implementation of surface tension force. We simulated the coalescence of two drops under zero-gravity condition and evaluated the mass conservation property of the level set method.

Development of a CFD Simulation Method for Extreme Wave and Structure Interactions

2005 ◽  
Author(s):  
Chi Yang ◽  
Rainald Lo¨hner ◽  
Solomon C. Yim
Keyword(s):  
Cfd Simulation ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Simulation Method ◽  
Computer Code ◽  
Dam Break ◽  
Navier Stokes ◽  
Extreme Waves ◽  
Cfd Method ◽  
Incompressible Euler

A robust Volume of Fluid (VOF) technique is presented together with an incompressible Euler/Navier Stokes solver operating on adaptive, unstructured grids to simulate the interactions of extreme waves and three-dimensional structures. The incompressible Euler/Navier Stokes equations are solved using projection schemes and a finite element method. The classic dam-break problem has been used to validate the computer code developed based on the method described above. The numerical simulations of a three dimensional dam-break wave interacting with a single cylinder and a cylinder array have been carried out. Computational results have demonstrated that the present CFD method is capable of simulating the interactions of extreme waves and three-dimensional structures, which are of great importance for the comprehension of many natural phenomena in marine, coastal and marine engineering.

Boundary integral method for the evolution of slender viscous fibres containing holes in the cross-section

2009 ◽  
Vol 621 ◽  
pp. 155-182 ◽  
Author(s):  
SRINATH S. CHAKRAVARTHY ◽  
WILSON K. S. CHIU
Keyword(s):  
Surface Tension ◽  
Cross Section ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Fibre Length ◽  
Boundary Integral ◽  
Boundary Integral Method ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Simply Connected

We consider the evolution of slender viscous fibres with cross-section containing holes with application to fabrication of microstructured optical fibres. The fibre evolution is driven by either prescribing velocity or a force at the ends of the fibre, and the free surfaces evolve under the influence of surface tension, internal pressurization, inertia and gravity. We use the fact that ratio of the typical fibre radius to the typical fibre length is small to perform an asymptotic analysis of the full three-dimensional Navier–Stokes equations similar to earlier work on non-axisymmetric (but simply connected) fibres. A numerical solution to the multiply connected steady-state drawing problem is formulated based on the solution the Sherman–Lauricella equation. The effects of different drawing and material parameters like surface tension, gravity, inertia and internal pressurization on the drawing are examined, and extension of the method to non-isothermal evolution is presented.

Effects of stator splitter blades on aerodynamic performance of a single-stage transonic axial compressor

2020 ◽  
Vol 14 (4) ◽  
pp. 7369-7378
Author(s):  
Ky-Quang Pham ◽  
Xuan-Truong Le ◽  
Cong-Truong Dinh
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Aerodynamic Performance ◽  
Numerical Results ◽  
Single Stage ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Operating Stability ◽  
Length Coverage

Splitter blades located between stator blades in a single-stage axial compressor were proposed and investigated in this work to find their effects on aerodynamic performance and operating stability. Aerodynamic performance of the compressor was evaluated using three-dimensional Reynolds-averaged Navier-Stokes equations using the k-e turbulence model with a scalable wall function. The numerical results for the typical performance parameters without stator splitter blades were validated in comparison with experimental data. The numerical results of a parametric study using four geometric parameters (chord length, coverage angle, height and position) of the stator splitter blades showed that the operational stability of the single-stage axial compressor enhances remarkably using the stator splitter blades. The splitters were effective in suppressing flow separation in the stator domain of the compressor at near-stall condition which affects considerably the aerodynamic performance of the compressor.

scholarly journals Numerical computation of blood flow for a patient-specific hemodialysis shunt model

2021 ◽  
Author(s):  
Surabhi Rathore ◽  
Tomoki Uda ◽  
Viet Q. H. Huynh ◽  
Hiroshi Suito ◽  
Toshitaka Watanabe ◽  
...  
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Arteriovenous Shunt ◽  
Navier Stokes ◽  
Patient Specific ◽  
Stabilized Finite Element ◽  
Computed Tomography Scanning ◽  
Outflow Boundary ◽  
Stage Renal Disease ◽  
End Stage

AbstractHemodialysis procedure is usually advisable for end-stage renal disease patients. This study is aimed at computational investigation of hemodynamical characteristics in three-dimensional arteriovenous shunt for hemodialysis, for which computed tomography scanning and phase-contrast magnetic resonance imaging are used. Several hemodynamical characteristics are presented and discussed depending on the patient-specific morphology and flow conditions including regurgitating flow from the distal artery caused by the construction of the arteriovenous shunt. A simple backflow prevention technique at an outflow boundary is presented, with stabilized finite element approaches for incompressible Navier–Stokes equations.

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