scholarly journals A Study on a VOF Method for the Improvement of Free Surface Capturing

2005 ◽  
Vol 42 (2) ◽  
pp. 88-97 ◽  
Keyword(s):  
Free Surface ◽  
Vof Method ◽  
Free Surface Capturing

An Improved Anti-Diffusive VOF Method to Predict Two-Fluid Free Surface Flows

2011 ◽  
Author(s):  
Y. G. Chen ◽  
W. G. Price ◽  
P. Temarel
Keyword(s):  
Free Surface ◽  
Diffusion Processes ◽  
Volume Fraction ◽  
Volume Of Fluid ◽  
Free Surface Flows ◽  
Vof Method ◽  
Advection Equation ◽  
Diffusion Term ◽  
Surface Flows ◽  
Two Fluid

This investigation continues the development of an anti-diffusive volume of fluid method [1] by improving accuracy through the addition of an artificial diffusion term, with a negative diffusion coefficient, to the original advection equation describing the evolution of the fluid volume fraction. The advection and diffusion processes are split into a set of two partial differential equations (PDEs). The improved anti-diffusive Volume of Fluid (VOF) method is coupled with a two-fluid flow solver to predict free surface flows and illustrated by examples given in two-dimensional flows. The first numerical example is a solitary wave travelling in a tank. The second example is a plunging wave generated by flow over a submerged obstacle of prescribed shape on a horizontal floor. The computational results are validated against available experimental data.

Simulations of Dam-Break Flows Using Free Surface Capturing Method

2008 ◽  
Vol 24 (4) ◽  
pp. 391-403 ◽  
Author(s):  
W.-Y. Chang ◽  
L.-C. Lee ◽  
H.-C. Lien ◽  
J.-S. Lai
Keyword(s):  
Free Surface ◽  
Stokes Equations ◽  
Variable Density ◽  
Dam Break ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Flow Equations ◽  
Weakly Compressible ◽  
Dam Break Flow ◽  
Free Surface Capturing

AbstractA model adopting the surface capturing method is developed for the simulation of dam-break flows by solving the Navier-Stokes equations of weakly compressible and variable density flows in open channels. Due to the characteristics of weakly compressible flow equations, a compressibility parameter describing the compressibility of fluid is determined to obtain the time-accurate flow fields in both liquid and gas regions simultaneously. Accordingly, the location of free surface can be captured as a discontinuity of the density field for dam-break flow simulations. The numerical algorithm in the proposed method is based on the framework of the finite volume method for discretization in space. To deal with the discontinuity property of fluid density near the free surface, the TVD-MUSCL scheme is adopted to overcome numerical oscillations and dissipation. For discretization in time, the explicit 4-stage Runge-Kutta scheme is employed in the model. Finally, several typical dam-break flow problems in open channel are simulated to demonstrate the validation and applicability of the proposed model.

A Stern Slamming Analysis Using Three-Dimensional CFD Simulation

2008 ◽  
Author(s):  
Kunho Kim ◽  
Yung S. Shin ◽  
Suqin Wang
Keyword(s):  
Free Surface ◽  
Cfd Simulation ◽  
Two Phase Flow ◽  
Three Dimensional ◽  
Phase Flow ◽  
Loading Conditions ◽  
Two Phase ◽  
Pressure Coefficients ◽  
Free Surface Capturing ◽  
Design Pressure

A stern slamming analysis based on three-dimensional computational fluid dynamics (CFD) simulation is presented with an application to a liquefied natural gas (LNG) carrier with twin skegs. This study includes; seakeeping analysis, statistical analysis for relative motions and velocities, three-dimensional slamming simulation by a CFD software, and structural assessment for plates and stiffeners. The stern areas are divided into panels in which relative velocity/motion and pressure coefficients are to be calculated. Seakeeping calculations are carried out in full load and ballast loading conditions at ship speeds of 0 and 5 knots. A series of equivalent 20-year return sea states in a wave scatter diagram are selected for environmental conditions. Extreme velocities are then evaluated from the loading conditions and the speeds considered with reference to the probability of slamming occurrence. Slamming simulations are carried out in a three-dimensional domain with a CFD software to calculate pressure coefficients. Two-phase flow with water and air is to be adopted in conjunction with free surface capturing method. Viscous laminar flow is assumed in simulation. Slamming design pressure is calculated by the pressure coefficients and the extreme velocities. Based on computed design pressure, an ultimate strength analysis is performed for the determination of required plate thickness. Also, required stiffener dimensions are determined by analytic formulas. As mentioned above, this approach has been applied to an LNG carrier with twin skegs. In the application, two-phase flow with water and air was adopted in conjunction with the volume-of-fluid method for free surface capturing. Mixed hexahedral and tetrahedral grids were employed. The computational case was determined from simulations of global ship motion. Maximum slamming pressure was found near the end of a skeg. Large pressure also can be observed in the stern overhang area. Generally slamming pressure decreases away from the stern.

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