scholarly journals The Requirement for Hydrostatic Initialisation in LS-DYNA/USA Finite Element Models

2000 ◽  
Vol 7 (2) ◽  
pp. 57-65
Author(s):  
Lloyd Hammond ◽  
Raphael Grzebieta
Keyword(s):  
Finite Element ◽  
Underwater Explosion ◽  
Element Model ◽  
Plate Structures ◽  
Fluid Structure ◽  
The Usa ◽  
Structural Responses ◽  
Fluid Boundary ◽  
Underwater Shock ◽  
Surrounding Fluid

The LS-DYNA/USA (Underwater Shock Analysis) coupled finite element codes are being investigated as a tool for predicting the local response of compliant plate structures subjected to far-field underwater explosion.It had previously been observed in LS-DYNA/USA models that extraneous pressure build-ups emanating from the DAA (doubly asymptotic approximation) boundaries may occur in the surrounding fluid region of the model, which inevitably lead to erroneous modelling of fluid-structure interaction and inaccurate structural responses. These instabilities typically result in divergence of the solution and eventually premature termination of the simulation. After a comprehensive investigation, it was found that the instabilities did not arise if the finite element model was hydrostatically initialised before conducting the LS-DYNA/USA simulation.The purpose of this study is to investigate the need for achieving hydrostatic equilibrium prior to the modelling of the shock wave propagation through the fluid-structure media. The method for achieving static equilibrium with the current version of the LS-DYNA/USA software is presented. The example simulations presented show that the hydrostatic initialisation procedure is effective in removing instabilities occurring at the DAA-fluid boundary, associated with the USA ambient hydrostatic pressure condition.

Active Control of Vibration and Noise Radiation from Fluid-Loaded Cylinder using Active Constrained Layer Damping

2002 ◽  
Vol 8 (6) ◽  
pp. 877-902 ◽  
Author(s):  
W. Laplante ◽  
T. Chen ◽  
A. Baz ◽  
W. Sheilds
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Acoustic Radiation ◽  
Sound Radiation ◽  
Element Model ◽  
Water Tank ◽  
Constrained Layer Damping ◽  
Active Constrained Layer Damping ◽  
Active Constrained Layer ◽  
Surrounding Fluid

Vibration and sound radiation from fluid-loaded cylindrical shells are controlled using patches of Active Constrained Layer Damping (ACLD). The performance and the enhanced damping characteristics via reduced vibrations and sound radiation in the surrounding fluid is demonstrated both theoretically and experimentally. A prime motivation for this work is the potential wide applications in submarines and torpedoes where acoustic stealth is critical to the effectiveness of missions. A finite element model is also developed to predict the vibration and the acoustic radiation in the surrounding fluid of the ACLD-treated cylinders. The developed model is used to study the effectiveness of the control and placement strategies of the ACLD in controlling the fluid-structure interactions. A water tank is constructed that incorporates test cylinders treated with two ACLD patches placed for targeting specific vibration modes. Using this arrangement, the effectiveness of different control strategies is studied when the submerged cylinders are subjected to internal excitation, and the radiated sound pressure level in the water is observed. Comparisons are made between the experimental results and the theoretical predictions to validate the finite element model.

Evaluation of the CSR-H Sloshing Criterion Using Direct Fluid Structure Calculation

2015 ◽  
Author(s):  
Po-Wen Wang ◽  
Chi-Fang Lee ◽  
Yann Quéméner ◽  
Chien-Hua Huang
Keyword(s):  
Finite Element ◽  
Fluid Dynamic ◽  
Plate Thickness ◽  
Structural Response ◽  
Element Model ◽  
Dynamic Responses ◽  
Interaction Technique ◽  
Time Step ◽  
Fluid Structure ◽  
Structural Rules

The objective of this study was to clarify the theoretical basis of sloshing loads and required plate thickness formulations in the harmonized common structural rules. This study used computational fluid dynamic (CFD) to calculate sloshing loads and used finite element analyses (FEA) to evaluate structural response. The sensitivity of the CFD predictions to the time step and grid size was also investigated. Cargo oil tanks were then selected in a handy size oil tanker and a very large crude carrier to evaluate the longitudinal and transverse sloshing loads on the tank boundaries. The results showed that the sloshing pressures computed at four filling levels were mostly consistent with CSR-H. Afterward, the sloshing pressure produced by CFD was applied to the finite element model by using a fluid-structure interaction technique to obtain the dynamic response of the structure. The dynamic responses were investigated to validate the quasistatic approach for sloshing assessment.

Bending Behavior of Plain-Woven Fabric Air Beams: Fluid-Structure Interaction Approach

2006 ◽  
Author(s):  
Paul V. Cavallaro ◽  
Ali M. Sadegh ◽  
Claudia J. Quigley
Keyword(s):  
Finite Element ◽  
Ideal Gas ◽  
Woven Fabric ◽  
Fluid Structure Interactions ◽  
Fluid Structure ◽  
Ideal Gas Law ◽  
Biaxial Tests ◽  
Structural Responses ◽  
Bending Behavior ◽  
Interaction Approach

A swatch of plain-woven fabric was subjected to biaxial tests and its material characterization was performed. The stress-strain relations of the fabric were determined and directly used in finite element models of an air beam, assumed constructed with the same fabric, subjected to inflation and bending events. The structural responses to these events were obtained using the ABAQUS-Explicit[1] finite element solver for a range of pressures including those considered typical in safe operations of air inflated structures. The models accounted for the fluid-structure interactions between the air and the fabric. The air was treated as a compressible fluid in accordance with the Ideal Gas Law and was subjected to adiabatic constraints during bending. The fabric was represented with membrane elements and several constitutive cases including linear elasticity and hyperelasticity were studied. The bending behavior for each constitutive case is presented and discussions for their use and limitations follow.

Shock-Resistance Research of Ship Structural Subjected to Underwater Explosion

2014 ◽  
Vol 945-949 ◽  
pp. 1180-1184
Author(s):  
Yao Guo Xie
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Cross Section ◽  
Critical Radius ◽  
Underwater Explosion ◽  
Element Model ◽  
Current Standard ◽  
Envelope Analysis ◽  
Shock Resistance ◽  
Selection Of

A finite element model ships, for example design test condition of the underwater explosion, selection of explosive package quantity is 1000KG TNT, the explosive location along the direction of the ship with the bow, midship and stern, the angle of attack in three exploded cross section have 90 degrees, 60 degrees, 45 degrees, 30 degrees and 0 degrees. According to the current standard to calculate the ship damage radius, critical radius and safety radius of specific values under the effect of underwater explosion, interpolation calculation and draw the envelope. Analysis shows that the vitality of ships and shock-resistance is not only related to the explosive distance, also related to the attack position.

Coupling Model Analysis on Fluid Structure Interaction in Lifting Pipeling Based on ADINA

2012 ◽  
Vol 468-471 ◽  
pp. 238-244
Author(s):  
Zhao Wang ◽  
Zhi Jin Zhou ◽  
Hao Lu ◽  
Ze Jun Wen ◽  
Yi Min Xia
Keyword(s):  
Finite Element ◽  
Natural Frequency ◽  
Volume Concentration ◽  
Natural Frequencies ◽  
Fluid Structure Interaction ◽  
Element Model ◽  
Structure Design ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Finite Element Software

Using finite element software ADINA, three coupling models on fluid-structure interaction among internal fluid—pipe—external fluid in the lifting pipeline were researched. Firstly, coupling finite element model on fluid structure interaction of lifting pipeline was established and the first sixth order natural frequencies and principal vibration modes were attained at different ore conveying volume concentration and cross-section size of pipeline;Then natural frequencies of three couplings were compared with two couplings and no coupling according to the above condition, and FSI effect on natural frequency of pipeline was discussed. The calculation results were shown that the natural frequency of the pipe and its relative error reduced with the volume concentration and the relative wall thickness increased, which explain the reason that has better accuracy considering three couplings than other .These results have certain directive significance on the dynamic response, structure design and study of reduction vibration of lifting pipeline.

A Fluid-Structure Coupled Computational Model for the Certification of Shock-Resistant Elastomer Coatings

2020 ◽  
Author(s):  
Wentao Ma ◽  
Xuning Zhao ◽  
Kevin Wang
Keyword(s):  
Finite Element ◽  
Computational Model ◽  
Finite Volume ◽  
Underwater Explosion ◽  
Material Behavior ◽  
Nonlinear Material ◽  
Structural Deformation ◽  
Mechanical And Thermal Properties ◽  
Dynamics Model ◽  
Fluid Structure

Abstract Shock waves from underwater and air explosions are significant threats to surface and underwater vehicles and structures. Recent studies on the mechanical and thermal properties of various phase-separated elastomers indicate the possibility of applying these materials as a coating to mitigate shock-induced structural failures. To demonstrate this approach and investigate its efficacy, this paper presents a fluid-structure coupled computational model capable of predicting the dynamic response of air-backed bilayer (i.e. elastomer coating – metal substrate) structures submerged in water to hydrostatic and underwater explosion loads. The model couples a three-dimensional multiphase finite volume computational fluid dynamics model with a nonlinear finite element computational solid dynamics model using the FIVER (FInite Volume method with Exact multi-material Riemann solvers) method. The kinematic boundary condition at the fluid-structure interface is enforced using an embedded boundary method that is capable of handling large structural deformation and topological changes. The dynamic interface condition is enforced by formulating and solving local, one-dimensional fluid-solid Riemann problems, which is well-suited for transferring shock and impulsive loads. The capability of this computational model is demonstrated through a numerical investigation of hydrostatic and shock-induced collapse of aluminum tubes with polyurea coating on its inner surface. The thickness of the structure is resolved explicitly by the finite element mesh. The nonlinear material behavior of polyurea is accounted for using a hyper-viscoelastic constitutive model featuring a modified Mooney-Rivlin equation and a stress relaxation function in the form of prony series. Three numerical experiments are conducted to simulate and compare the collapse of the structure in different loading conditions, including a constant pressure, a fluid environment initially in hydrostatic equilibrium, and a two-phase fluid flow created by a near-field underwater explosion.

Sign in / Sign up

Export Citation Format

Share Document