Numerical study of the interaction between a pulsating coated microbubble and a rigid wall. II. Trapped pulsation

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
M. Vlachomitrou ◽  
N. Pelekasis
Keyword(s):  
Numerical Study ◽  
Rigid Wall

Numerical Study of Stability and Accuracy of the Immersed Boundary Method Coupled to the Lattice Boltzmann BGK Model

2014 ◽  
Vol 16 (1) ◽  
pp. 136-168 ◽  
Author(s):  
Yongguang Cheng ◽  
Luoding Zhu ◽  
Chunze Zhang
Keyword(s):  
Lattice Boltzmann ◽  
Numerical Study ◽  
Rigid Wall ◽  
Segment Length ◽  
Immersed Boundary ◽  
Coupling Scheme ◽  
Circular Membrane ◽  
Shearing Flow ◽  
Dirac Delta ◽  
Forcing Term

AbstractThis paper aims to study the numerical features of a coupling scheme between the immersed boundary (IB) method and the lattice Boltzmann BGK (LBGK) model by four typical test problems: the relaxation of a circular membrane, the shearing flow induced by a moving fiber in the middle of a channel, the shearing flow near a non-slip rigid wall, and the circular Couette flow between two inversely rotating cylinders. The accuracy and robustness of the IB-LBGK coupling scheme, the performances of different discrete Dirac delta functions, the effect of iteration on the coupling scheme, the importance of the external forcing term treatment, the sensitivity of the coupling scheme to flow and boundary parameters, the velocity slip near non-slip rigid wall, and the origination of numerical instabilities are investigated in detail via the four test cases. It is found that the iteration in the coupling cycle can effectively improve stability, the introduction of a second-order forcing term in LBGK model is crucial, the discrete fiber segment length and the orientation of the fiber boundary obviously affect accuracy and stability, and the emergence of both temporal and spatial fluctuations of boundary parameters seems to be the indication of numerical instability. These elaborate results shed light on the nature of the coupling scheme and may benefit those who wish to use or improve the method.

A Composite Consisting of a Set of Hexagonal Ceramic Bars - The Numerical Study of the Ballistic Resistance

2011 ◽  
Vol 471-472 ◽  
pp. 1142-1146 ◽  
Author(s):  
Sebastian Stanislawek ◽  
Andrzej Morka ◽  
Tadeusz Niezgoda
Keyword(s):  
Reference Model ◽  
Numerical Study ◽  
Rigid Wall ◽  
Material Behavior ◽  
Aluminum Plate ◽  
Three Dimension ◽  
Projectile Impact ◽  
Ballistic Resistance ◽  
Behavior Simulation ◽  
The Impact

The paper presents a numerical study of a double layer composite panels impacted by a AP (Armor Piercing) 51WC projectile. The standard panel is built with aluminum and Al2O3 ceramic continuum layers while the studied model consists of the same aluminum plate but the front one is built with a set of hexagonal ceramic bars. The bar width and the impact position influence on the ballistic resistance are analyzed and compared with the reference solution. The problem has been solved with the usage of the modeling and simulation methods as well as finite elements method implemented in LS-DYNA software. Space discretization for each option was built by three dimension elements guarantying satisfying accuracy of the calculations. For material behavior simulation specific models including the influence of the strain rate and temperature changes were considered. Projectile Tungsten Curbide and aluminum plate material were described by Johnson-Cook model and ceramic target by Johnson-Holmquist model. In the studied panels the area surrounding back edges was supported by a rigid wall. The obtained results show interesting properties of the examined structures considering their ballistic resistance. All tests has given clear results about ballistic protection panel response under WC projectile impact. Panels consisting of sets of hexagonal ceramic bars are slightly easier to penetrate, reference model is stronger by 19% for smaller bars and by only 7% for bigger rods. Despite this fact, the ceramic layer is much less susceptible to overall destruction what makes it more applicable for the armor usage. Furthermore, little influence of the projectile impact point and consequently a part of the bar which is first destroyed is proved.

Multisphere Ceramic Composite Concept and its Numerical Study of the Ballistic Response

2011 ◽  
Vol 471-472 ◽  
pp. 1136-1141 ◽  
Author(s):  
Sebastian Stanislawek ◽  
Andrzej Morka ◽  
Tadeusz Niezgoda
Keyword(s):  
Reference Model ◽  
Numerical Study ◽  
Rigid Wall ◽  
Material Behavior ◽  
Material Strength ◽  
Three Dimension ◽  
Sphere Surface ◽  
Convex Shape ◽  
Behavior Simulation ◽  
The Impact

Numerical investigations were performed to determine the influence of the spherical convex shape ceramic - alumina composite in reference to the standard double layer panel. All versions of the target were verified in an impact test including influence upon the position of the AP (Armor Piercing) 7,62x51HHS impact. The crucial parameter which was used for this verification was change in time of the PROJECTILE kinetic energy. The problem has been solved with the usage of the modeling and simulation methods as well as finite elements method implemented in LS-DYNA software. Space discretization for each option was built by three dimension elements guarantying satisfying accuracy of the calculations. For material behavior simulation specific models including the influence of the strain rate and temperature changes were considered. Projectile’s core made of HHS and aluminum plate material were described by Johnson-Cook model and ceramic target with Johnson-Holmquist model. In the studied panels the area surrounding back edges was supported by rigid wall. The obtained results show interesting properties of the new structures considering their ballistic resistance. However only certain places were chosen for tests, the protection ability against projectile attack is in general higher than the reference model. What is particularly interesting during the 6.6mm from the sphere center impact the sphere surface trajectory deviation effect is present. A projectile is not stopped here by material strength but the front layer shape. Moreover it can be assumed that this phenomenon will take place on majority of points on the sphere surface. Despite this fact, a ceramic multi sphere layer is less susceptible to overall destruction, depending on the impact point. The results of those numerical simulations can be used for designing of modern armor protection systems against hard kinetic projectiles.

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.

Impact behaviour of elastoplastic spheres with a rigid wall

2000 ◽  
Vol 214 (8) ◽  
pp. 1107-1114 ◽  
Author(s):  
L-Y Li ◽  
C Thornton ◽  
C-Y Wu
Keyword(s):  
Contact Force ◽  
Numerical Study ◽  
Rigid Wall ◽  
Coefficient Of Restitution ◽  
Two Dimensional ◽  
Material Behaviour ◽  
Normal Impact ◽  
Dimensional Finite Element ◽  
The Impact ◽  
Force Displacement

The paper presents a numerical study of the normal impact of elastoplastic spheres with a rigid wall. The analysis is performed by employing DYNA2D, a non-linear, explicit, two-dimensional finite element (FE) code for impact mechanics. Deformations, time evolution of the contact force and contact force-displacement relationships during the impact are presented. Influences of material behaviour are discussed and their effect on the coefficient of restitution is also demonstrated.

Parametric Study of the Effect of Hinged Connectors on the Behavior of Origami-Inspired Structures Comprised of Sandwich Panels

2015 ◽  
Author(s):  
Zach C. Ballard ◽  
Ashley P. Thrall ◽  
Brian J. Smith
Keyword(s):  
Parametric Study ◽  
Numerical Study ◽  
Sandwich Panels ◽  
Rigid Wall ◽  
Fiber Reinforced Polymer ◽  
Structural Performance ◽  
Uniform Load ◽  
Reinforced Polymer ◽  
Relative Placement ◽  
The Impact

Origami can be a source of inspiration for rapidly deployable, rigid wall shelters. Folding panels comprised of sandwich panels will result in a lightweight, transportable design. The design of connections between panels is critical to the overall structural performance, but can pose a major design challenge. This paper investigates the implementation of hinges for connections between panels. A single panel, comprised of fiber-reinforced polymer faces and a foam core, is restrained by aluminum hinged connectors and subjected to a uniform load. An exhaustive parametric study is performed using a numerical model previously validated by experimental data. The numerical study will facilitate better understanding of the impact of the 1) number, 2) size, and 3) relative placement of connectors on panel behavior, with data comparisons focusing on the longitudinal surface strains and displacements of the panel. This investigation culminates in a set of guidelines for hinged connectors in origami-inspired structures.

Numerical study of acoustically driven bubble cloud dynamics near a rigid wall

2018 ◽  
Vol 40 ◽  
pp. 944-954 ◽  
Author(s):  
Jingsen Ma ◽  
Chao-Tsung Hsiao ◽  
Georges L. Chahine
Keyword(s):  
Numerical Study ◽  
Rigid Wall ◽  
Bubble Cloud ◽  
Cloud Dynamics
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