scholarly journals Numerical Study of the Interaction between a Collapsing Bubble and a Movable Particle in a Free Field

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3331
Author(s):  
Yuxin Zheng ◽  
Linya Chen ◽  
Xiaoyu Liang ◽  
Hangbo Duan
Keyword(s):  
Numerical Study ◽  
Free Field ◽  
Grid Method ◽  
Rigid Wall ◽  
Force Balance ◽  
Balance Model ◽  
Initial Distance ◽  
Overset Grid Method ◽  
Spherical Bubbles ◽  
Analytical Result

This study numerically investigates the interactions between a collapsing bubble and a movable particle with a comparable size in a free field, which is associated with the microscopic mechanisms of the synergetic effects of cavitation erosion and particle abrasion on the damages of materials in fluid machineries. A new solver on OpenFOAM based on direct numerical simulations with the volume of fluid (VOF) method capturing the interface of a bubble and with the overset grid method handling the motion of the particle was developed to achieve the fluid–structure interaction (FSI). The results show that bubbles in cases with stand-off parameter χ (defined as (d0−Rp)/R0), where d0 is the initial distance between the centers of the bubble and particle, and Rp,R0 are the particle’s radius and the initial radius of the bubble respectively >1, experience spherical-shaped collapse under the influence of the approaching particle, which is attracted by the collapsing bubble. The bubbles in these cases no longer present non-spherical collapse. Additionally, a force balance model to account for the particle dynamics was established, in which the particle velocity inversely depends on the size of the particle, and approximately on the second power of the initial distance from the bubble. This analytical result accords with the numerical results and is valid for cases with χ>1 only, since it is based on the theory of spherical bubbles. These conclusions are important for further study of the interactions between a bubble and a movable particle near a rigid wall.

2D Numerical Study on Wake Scenarios for a Flapping Foil

2021 ◽  
Author(s):  
Hui-li Xu ◽  
Marilena Greco ◽  
Claudio Lugni
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Stokes Equations ◽  
Numerical Study ◽  
Grid Method ◽  
Navier Stokes ◽  
Flapping Foil ◽  
Von Karman ◽  
Overset Grid Method ◽  
Von Kármán

Abstract Fishes are talented swimmers. Depending on the propulsion mechanisms many fishes can use flapping tails and/or fins to generate thrust, which seems to be connected to the formation of a reverse von Kármán wake. In the present work, the flow past a 2D flapping foil is simulated by solving the incompressible Navier-Stokes equations in the open-source OpenFOAM platform. A systematic study by varying the oscillating frequency, peak-to-peak amplitude and Reynolds number has been performed to analyze the transition of vorticity types in the wake as well as drag-thrust transition. The overset grid method is used herein to allow the pitching foil to move without restrictions. Spatial convergence tests have been carried out with respect to grid resolution and the size of overset mesh domain. Numerical results are compared with available experimental data and discussed. The results show that the adopted methodology can be well applied to simulate large amplitude motions of the flapping foil. The transitions in the types of wake are consistent with the benchmark experimental data, and the drag-thrust transition of the pitching foil does not coincide with von Kármán (vK)-reverse von Kármán (reverse-vK) wake transition and it is highly dependent on the Reynolds number.

Numerical simulation of an X-wing flapping wing MAV by means of a deforming overset grid method

2015 ◽  
Author(s):  
Shuanghou Deng ◽  
Tianhang Xiao ◽  
Mustafa Percin ◽  
Bas van Oudheusden ◽  
Hester Bijl ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Grid Method ◽  
Flapping Wing ◽  
Overset Grid ◽  
Overset Grid Method

Prediction of Slamming Loads on Catamaran Wetdeck Using CFD

2015 ◽  
Author(s):  
Ahmed Swidan ◽  
Giles Thomas ◽  
Dev Ranmuthugala ◽  
Irene Penesis ◽  
Walid Amin ◽  
...  
Keyword(s):  
Model Simulation ◽  
Three Dimensional ◽  
Grid Method ◽  
Computationally Efficient ◽  
Overset Grid ◽  
Force Magnitude ◽  
Overset Grid Method ◽  
Drop Tests ◽  
Transient Velocity ◽  
Transient Velocity Profile

Wetdeck slamming is one of the principal hydrodynamic loads acting on catamarans. CFD techniques are shown to successfully characterise wetdeck slamming loads, as validated through a series of controlled-speed drop tests on a three-dimensional catamaran hullform model. Simulation of water entry at constant speed by applying a fixed grid method was found to be more computationally efficient than applying an overset grid. However, the overset grid method for implementing the exact transient velocity profile resulted in better prediction of slam force magnitude. In addition the splitting force concurrent with wetdeck slam event was quantified to be 21% of the vertical slamming force.

scholarly journals A force balance model for the motion, impact, and bounce of bubbles

2014 ◽  
Vol 26 (9) ◽  
pp. 092101 ◽  
Author(s):  
Evert Klaseboer ◽  
Rogerio Manica ◽  
Maurice H. W. Hendrix ◽  
Claus-Dieter Ohl ◽  
Derek Y. C. Chan
Keyword(s):  
Force Balance ◽  
Balance Model
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