A Moving Grid Model for Simulation of Free Surface Behavior Induced by Horizontal Cylinders Exit and Entry

Huang

Engineering Applications of Computational Fluid Mechanics

et al. 2015

Three-dimensional numerical simulations are performed to analyze the effect of the aspect ratio Ar and axial magnetic field on thermocapillary convection in liquid bridges with deformable freesurface under microgravity, in which the volume of fluid (VOF) method is adopted to track the free-surface movement. The simulation results elucidate that the oscillation wave number m and frequency of temperature fluctuation decrease with increasing Ar, while the amplitude of temperature fluctuation increases with increasing Ar. The deformation ratio ξ of the free-surface increases as Ar increases. The numerical results also reveal that the axial magnetic field causes a concentration of convection vortexes near the free-surface and effectively suppresses the flow in both the radial and axial directions. Moreover, the axial magnetic field effectively damps free-surface deformation, so that the deformation ratio ξ decreases as the Hartmann number Ha increases. The temperature displays a uniform and linear distribution along the free-surface and the axis of molten zone when B a = 0.3 T. ARTICLE HISTORYintensity of the applied axial magmatic fields (T) Ca Capillary number, Ca =

Section: Methodsmentioning

confidence: 99%

The effect of aspect ratio and axial magnetic field on thermocapillary convection in liquid bridges with a deformable free-surface

Huang

Engineering Applications of Computational Fluid Mechanics

et al. 2015

Engineering Applications of Computational Fluid Mechanics

“…In recent years, research on the water-emerging process of vehicles and their control techniques has gradually increased. However, most of these works focus on deterministic results with approximate flow conditions and neglect the existence of uncertainty (Mnasri, Hafsia, Omri, & Maalel, 2010;Qi, Feng, Xu, Zhang, & Li, 2016;Shereena, Vengadesan, Idichandy, & Bhattacharyya, 2013). However, it seems extremely dangerous for this situation that a launch system has a good performance estimate with a large confidence interval (Levy, 2005).…”

Section: Introductionmentioning

confidence: 99%

Effect of a pressure-equalizing film on the trajectory and attitude robustness of an underwater vehicle considering the uncertainty of the platform velocity

Chen

et al. 2018

A vertically moving underwater vehicle with an air film attached to its exterior can significantly weaken the hydrodynamic disturbances caused by launch conditions. To quantify the ability of a pressure-equalizing film to improve the trajectory and attitude robustness of vehicles under an uncertain platform velocity input, the response surface model of nonintrusive polynomial chaos was built based on sample spacing constructed with a nested sparse grid-based stochastic collocation method. The results indicate the uncertainty bars of the horizontal displacement exhibit an expanding-contracting-expanding pattern with a 'spindle' shape as the vehicle moves. In contrast, the horizontal velocity presents an 'hourglass' shape. Additionally, the horizontal velocity and the pitching angular velocity of the vehicle are quite sensitive to the uncertainty of the platform velocity, and the large mean value and uncertainty of these factors will statistically worsen the trajectory and attitude of the vehicle. Implementation of an exhaust during the water-emerging process can weaken the horizontal motion and pitching rotation of a vehicle, as well as the relevant uncertainty. This is attributed to a generated pressure-equalizing region with a low uncertainty. Thus, an exhaust is urgently needed in the water-emerging process of these vehicles.

Modelling and Simulation in Engineering

“…Advances in computer technology and CFD have made it possible to use commercial CFD codes to solve wave impact problem. For example, Mnasri et al used Fluent code with a moving grid to analyze the free surface evolution induced by one or two moving cylinders [17]. Chen et al studied water entry of a horizontal cylinder based on VOF method by Fluent [18].…”

Section: Modelling and Simulation In Engineeringmentioning

confidence: 99%

Numerical Modeling and Simulation of Wave Impact of a Circular Cylinder during the Submergence Process

Jiang

Cai

2017

Wave slamming loads on a circular cylinder during water entry and the subsequence submergence process are predicted based on a numerical wave load model. The wave impact problems are analyzed by solving Reynolds-Averaged Navier-Stokes (RANS) equations and VOF equations. A finite volume approach (FV) is employed to implement the discretization of the RANS equations. A two-dimensional numerical wave tank is established to simulate regular ocean waves. The wave slamming problems are investigated by deploying a circular cylinder into waves with a constant vertical velocity. The present numerical method is validated using other numerical or theoretical results in accordance with varying free surface profiles when a circular cylinder sinks in calm water. A numerical example is given to show the submergence process of the circular cylinder in waves, and both free surface profiles and the pressure distributions on the cylinder of different time instants are obtained. Time histories of hydrodynamic load on the cylinder during the submergence process for different wave impact angles, wave heights, and wave periods are obtained, and results are analyzed in detail.