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Effect of thresholding algorithms on pervious pavement skid resistance
Published in A. Kumar, A.T. Papagiannakis, A. Bhasin, D. Little, Advances in Materials and Pavement Performance Prediction II, 2020
A. Jagadeesh, G. P. Ong, Y. M. Su
A skid resistance simulation model was developed using ANSYS Static Structure, CFX and Fluid Structure Interaction tools. It consists of two sub-models: the tire-pavement sub-model and the fluid sub-model. The tire-pavement sub-model consists of a rigid smooth pavement surface and a single layered tire model (ASTM E524 smooth tire), and the fluid sub-model consists of the pervious pavement pores obtained from XRCT and fluid zone under the tread. Figure 3 shows the tire-pavement and fluid sub-models. The fluid sub-model consists of the Navier-Strokes equations with consideration to k-ε turbulence model, and multiphase modelling using the Volume of Fluid method. The footprint area calibration was carried out to obtain the unknown shell thickness properties. More details on the material properties and boundary conditions can be found in Zhang et al. (2014).
Computational Heat Transfer
Published in Greg F. Naterer, Advanced Heat Transfer, 2018
The volume of fluid method (VOF method; Hirt and Nichols 1981) is a common method for predicting and analyzing free surface flows. In this method, a fluid fraction, F, is defined within each discrete cell (finite volume or element) of the mesh. Values of F = 1, F = 0, and 0 < F < 1 represent a full cell, empty cell, and cell that contains a free surface, respectively (see Figure 10.7). Marker particles are defined as cell intersection points that identify where the fluid is located in a cell. The perpendicular direction to the free surface lies in the direction of the gradient of F. Once both the normal direction and value of F in a boundary cell are known, a line through the cell can be constructed to approximate the free surface. Boundary conditions, including surface tension forces, can then be applied at the free surface.
Modelling of coastal and nearshore structures and processes
Published in P. Novak, V. Guinot, A. Jeffrey, D.E. Reeve, Hydraulic Modelling – an Introduction, 2010
P. Novak, V. Guinot, A. Jeffrey, D.E. Reeve
Until fairly recently, simulating wave overtopping using the Navier–Stokes equations was beyond both the computational power of available computers and the numerical methods required to capture the intricacies of wave breaking. Not only was it necessary to be able to describe wave overturning, but it was also necessary to describe the rapid energy dissipation caused by the highly turbulent flow in broken waves. The development of the ‘volume of fluid’ method, described by Hirt and Nichols (1981), was a major breakthrough in modelling highly distorted flows. The simulation of turbulence required the solution of ‘turbulence equations’ simultaneously with an averaged form of the Navier–Stokes equations, the ‘Reynolds averaged Navier–Stokes equations’, (RANS), (see also Section 4.3.3).
Numerical Studies of Separation Performance of Knelson Concentrator for Beneficiation of Fine Coal
Published in International Journal of Coal Preparation and Utilization, 2021
Licheng Ma, Lubin Wei, Xueshuai Zhu, Darong Xu, Xinyu Pei, Hongchao Xue
Although the incompressible assumption is made for simplification of differential equation solving, the liquid density is not constant in rotation bowl, and it is calculated on the basis of the ideal liquid law. A major difficulty in the flow field computation is the free surface of the film which yields a boundary condition whose position is unknown until the problem is fully solved. The Volume of Fluid method is used for solves the physics continuously between the liquid and gas phases by weighing them according to their respective local volume fractions. This method would make it possible to compute the flowing film thinning along the bowl wall. In this study, the pressure staggered option was used as the pressure interpolation scheme and semi-implicit pressure-linked equations algorithm scheme was used for the calculation of the pressure and velocity fields. Finite volume method was used for the discretization of the governing equations and all physical quantities at the grid node were calculated according to the values at the neighboring control volume surfaces through the quadratic upwind interpolation convective kinematics scheme. Time step size was determined as 0.005 s for the solution. When the residuals of the predicted velocities and volume fraction of the air phase were smaller than 10−3 and other variables’ residuals were smaller than 10−5, convergence was considered to have been reached.
Large-eddy simulation of supercritical free-surface flow in an open-channel contraction
Published in Journal of Hydraulic Research, 2022
Filipa Adzic, Thorsten Stoesser, Yan Liu, Zhihua Xie
The volume of fluid (VOF) method uses scalar functions to compute the free surface location, which makes it significantly less computationally demanding than particle methods. The volume of fluid method was introduced by Hirt and Nichols (1981). Variations of the method have been emerging (Boris & Book, 1973; Noh & Woodward, 1979; Ubbink, 1997; Youngs et al., 1982) with the objective of improving the accuracy of the original method. Few researchers employed the volume of fluid method with LES (Sanjou & Nezu, 2010; Shi et al., 2000; Xie et al., 2014) and mostly focused on flow with relatively simple geometries; however, by including immersed boundary and cut-cell approaches complex 3D flows have been presented (Xie, 2015; Xie & Stoesser, 2020; Yan et al., 2019).
Numerical study and acoustic analysis of propeller and hull surface vessel in self-propulsion mode
Published in Ships and Offshore Structures, 2022
Mehdi Raghebi, Majid Norouzi Keshtan, Majid Malek Jafarian, Mohammad Reza Bagheri
The volume of fluid method is a numerical technique for tracking and locating the free surface (or fluid–fluid interface) (Wang 2014). It belongs to a class of techniques that study the free surface of the fluid by examining the fluid-grid volume fraction function in the grid cells and tracking fluid changes instead of moving particles on the free surface As long as the value of the function in each grid of the flow field is known, the interface line of the motion can be traced. Suggesting the whole computational domain is defined as; the main flow of the fluid is defined as ; The second phase fluid is defined as, the volume of fluid function is defined as follows: Moreover, in a flow field consisting of two insoluble fluids, the fluid velocity field is defined as. The function corresponds to: In each grid, is the integer of on the grid, which is defined as. The volume of Fluid is according to Equation 6: It is evident that fluids in grids are all secondary phases when; the grids are filled with the main phase fluid when; and grids include interface fluid when.