Simulation of Multi-Mode Film Boiling Using Level Set Method

2009 ◽  
Author(s):  
Vinesh H. Gada ◽  
Atul Sharma
Keyword(s):  
Film Thickness ◽  
Level Set ◽  
Taylor Instability ◽  
Viscous Force ◽  
Film Boiling ◽  
Inertia Force ◽  
Initial Film ◽  
Wall Superheat ◽  
Rayleigh Taylor Instability ◽  
Multi Mode

2D transient multi-mode film boiling simulation of water near critical pressure (p = 0.99pc = 21.9 MPa) on a heated horizontal surface is carried out using an in-house Level Set (LS) method based semi-explicit finite volume method code. The influence of initial vapor film thickness (yo) on the dominant instability mode is evaluated by carrying out simulations on domain having width greater than most dangerous Taylor wavelength i.e. LX = 4λd with y0 = 0.0425λd and 0.125λd at low wall superheat (ΔT = 2K). For lower initial film thickness, the viscous force dominated Rayleigh-Taylor instability is captured and the average bubble spacing is found close to the prediction made using lubrication theory i.e. λP = 2λc = 0.816λd. However, for higher initial film thickness, the inertia force dominated Taylor-Helmholtz mode of instability is found with the average bubble spacing close to λd. Simulations are carried out to check the existence of Rayleigh-Taylor instability on various domain width LX = 2λd, 3λd, 4λd and 6λd at yo = 0.0425λd and ΔT = 2K. The average bubble spacing for all domain widths is found to be less than 2λc indicating that the Rayleigh-Taylor instability is dominant.

NUMERICAL SIMULATION OF RAYLEIGH–TAYLOR INSTABILITY BASED ON AN IMPROVED PARTICLE LEVEL SET METHOD

2014 ◽  
Vol 11 (04) ◽  
pp. 1350094 ◽  
Author(s):  
HUI TIAN ◽  
GUOJUN LI ◽  
XIONGWEN ZHANG
Keyword(s):  
Level Set Method ◽  
Level Set ◽  
Stokes Equations ◽  
Density Ratio ◽  
Immiscible Fluids ◽  
Taylor Instability ◽  
Wide Range ◽  
Particle Level ◽  
Rayleigh Taylor Instability ◽  
Particle Level Set Method

An improved particle correction procedure for particle level set method is proposed and applied to the simulation of Rayleigh–Taylor instability (RTI) of the incompressible two-phase immiscible fluids. In the proposed method, an improved particle correction method is developed to deal with all the relative positions between escaped particles and cell corners, which can reduce the disturbance arising in the distance function correction process due to the non-normal direction movement of escaped particles. The improved method is validated through accurately capturing the moving interface of the Zalesak's disk. Furthermore, coupled with the projection method for solving the Navier–Stokes equations, the time-dependent evolution of the RTI interface over a wide range of Reynolds numbers, Atwood numbers and Weber numbers are numerically investigated. A good agreement between the present results and the existing analytical solutions is obtained and the accuracy of the proposed method is further verified. Moreover, the effects of control parameters including viscosity, density ratio, and surface tension coefficient on the evolution of RTI are analyzed in detail, and a critical Weber number for the development of RTI is found.

scholarly journals A Relaxation Filtering Approach for Two-Dimensional Rayleigh–Taylor Instability-Induced Flows

Fluids ◽  
2019 ◽  
Vol 4 (2) ◽  
pp. 78 ◽  
Author(s):  
Sk. Mashfiqur Rahman ◽  
Omer San
Keyword(s):  
High Resolution ◽  
Numerical Experiments ◽  
Single Mode ◽  
Taylor Instability ◽  
Two Dimensional ◽  
Reconstruction Scheme ◽  
Rayleigh Taylor Instability ◽  
Multi Mode ◽  
Filtering Approach ◽  
Point Stencil

In this paper, we investigate the performance of a relaxation filtering approach for the Euler turbulence using a central seven-point stencil reconstruction scheme. High-resolution numerical experiments are performed for both multi-mode and single-mode

Numerical Simulation of Rayleigh-Taylor Instability With Two-Fluid Model and Interface Sharpening

2008 ◽  
Author(s):  
Luka Sˇtrubelj ◽  
Iztok Tiselj
Keyword(s):  
Free Surface ◽  
Level Set ◽  
Fluid Model ◽  
Free Surface Flows ◽  
Taylor Instability ◽  
Surface Flows ◽  
Interface Diffusion ◽  
Rayleigh Taylor Instability ◽  
Two Fluid Model ◽  
Two Fluid

The free surface flows are successfully modeled with one of the existing free surface models, such as: level set method, volume of fluid method, front tracking method, two-fluid model (two momentum equations) with modified interphase force and some others. The main disadvantage of the two-fluid model used for simulations of free surface flows is numerical diffusion of the interface, which can be significantly reduced as presented in this paper. The interface is sharpened with the conservative level set method, where after the advection step of volume fraction the numerical diffusion of the interface is reduced in such a way that the thickness of the interface is kept constant during the simulation. The reduction of the interface diffusion can also be called interface sharpening. In the present paper the two-fluid model with interface sharpening is validated with Rayleigh-Taylor instability. Under assumptions of isothermal and incompressible flow of two immiscible fluids, we simulated a system with the fluid of higher density located above the fluid of smaller density in two dimensions. Due to the gravity in the system, the fluid with a higher density moves below the fluid with a smaller density. The initial condition is not a flat interface between the fluids, but a cosine wave with small amplitude, which develops into a mushroom-like structure. Mushroom-like structure in simulation of Rayleigh-Taylor instability later develops into small droplets as result of numerical dispersion of interface (interface sharpening) or to narrow trails with interface diffusion (no interface sharpening). The results of the two-fluid model with interface sharpening are compared to two-fluid model without interface sharpening and single-fluid-model with/without interface sharpening. The analytic solution of amplitude growth can be found for small amplitudes and was also compared to simulation.

Numerical Simulation of Film Boiling Near Critical Pressures With a Level Set Method

1998 ◽  
Vol 120 (1) ◽  
pp. 183-192 ◽  
Author(s):  
G. Son ◽  
V. K. Dhir
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Level Set Method ◽  
Level Set ◽  
Vapor Phase ◽  
Film Boiling ◽  
Release Pattern ◽  
Wall Superheat ◽  
Change Effect ◽  
Good Agreement

Attempts have recently been made to numerically simulate film boiling on a horizontal surface. It has been observed from experiments and numerical simulations that during film boiling the bubbles are released alternatively at the nodes and antinodes of a Taylor wave. Near the critical state, however, hydrodynamic transition in bubble release pattern has been reported in the literature. The purpose of this work is to understand the mechanism of the transition in bubble release pattern through complete numerical simulation of the evolution of the vapor-liquid interface. The interface is captured by a level set method which is modified to include the liquid-vapor phase change effect. It is found from the numerical simulation that at low wall superheats the interface moves upwards, bubbles break off, and the interface drops down alternatively at the nodes and antinodes. However, with an increase in wall superheat, stable vapor jets are formed on both the nodes and antinodes and bubbles are released from the top of the vapor columns. The numerical results are compared with the experimental data, and visual observations reported in the literature are found to be in good agreement with the data.

scholarly journals Numerical and Experimental Analysis of the Growth of Gravitational Interfacial Instability Generated by Two Viscous Fluids of Different Densities

2013 ◽  
Vol 2013 ◽  
pp. 1-11
Author(s):  
Snehamoy Majumder ◽  
Debajit Saha ◽  
Partha Mishra
Keyword(s):  
Level Set Method ◽  
Level Set ◽  
Gravitational Instability ◽  
Physical Phenomenon ◽  
Taylor Instability ◽  
Interfacial Instability ◽  
Heaviside Function ◽  
Two Fluids ◽  
Gravity Driven ◽  
Rayleigh Taylor Instability

In the geophysical context, there are a wide variety of mechanisms which may lead to the formation of unstable density stratification, leading in turn to the development of the Rayleigh-Taylor instability and, more generally, interfacial gravity-driven instabilities, which involves moving boundaries and interfaces. The purpose of this work is to study the level set method and to apply the process to study the Rayleigh-Taylor instability experimentally and numerically. With the help of a simple, inexpensive experimental arrangement, the R-T instability has been visualized with moderate accuracy for real fluids. The same physical phenomenon has been investigated numerically to track the interface of two fluids of different densities to observe the gravitational instability with the application of level set method coupled with volume of fraction replacing the Heaviside function. Good agreement between theory and experimental results was found and growth of instability for both of the methods has been plotted.

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