scholarly journals Large-Amplitude Sloshing With Submerged Blocks

1990 ◽  
Vol 112 (1) ◽  
pp. 104-108 ◽  
Author(s):  
A. Huerta ◽  
W. K. Liu
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Nonlinear Behavior ◽  
Forced Vibrations ◽  
Element Formulation ◽  
Arbitrary Lagrangian Eulerian ◽  
Water Pool ◽  
Surface Motion ◽  
Structure Interaction ◽  
Interaction Problem

The computer simulation of forced vibrations induced on a water pool is presented in this paper. The complexity of the seismic fluid-structure interaction problem is accentuated by the large free surface motion. To overcome this difficulty, the arbitrary Lagrangian Eulerian (ALE) finite element formulation is employed. Moreover, the nonlinear behavior of the free surface motion is also taken into account. The results of the numerical simulation are compared with published experimental data and the effectiveness of the ALE algorithm is demonstrated.

Numerical and experimental studies on extrudate swell of branched polyethylene through axisymmetric and planar dies

2011 ◽  
Vol 31 (2-3) ◽  
Author(s):  
Vivek Ganvir ◽  
Basavarsu Gautham ◽  
Rochish Thaokar ◽  
Ashish Lele ◽  
Harshwardhan Pol
Keyword(s):  
Experimental Data ◽  
Experimental Studies ◽  
Uniaxial Extension ◽  
Video Camera ◽  
Element Formulation ◽  
Arbitrary Lagrangian Eulerian ◽  
Good Match ◽  
Extrudate Swell ◽  
Branched Polyethylene ◽  
On Line

Abstract Extrudate swell is simulated using an Arbitrary Lagrangian Eulerian (ALE) technique based finite element formulation and the same has been validated by comparing the results with reported numerical and experimental studies. In the present work we compare our ALE simulations with our own experimental data on the extrudate swell of commercial grade low density polyethylene (LDPE) resin. The resins were characterized for their rheological behavior in both shear and uniaxial extension. The polymers were extruded from a capillary under isothermal conditions and the extrudates were observed on-line using a video camera. ALE simulations were performed using molecular constitutive model like eXtended Pom–Pom (XPP) for branched (LDPE). The simulated extrudate swell was a good match with the experimental data. It was found that the swell values of LPDE through planar die are higher than the axisymmetric die.

Numerical Simulation of Twin-Parachute Inflation Process for Aircraft Ejection Escape

2020 ◽  
Author(s):  
Liwu Wang ◽  
Mingzhang Tang ◽  
Sijun Zhang
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Numerical Model ◽  
Physical Models ◽  
The Other ◽  
Arbitrary Lagrangian Eulerian ◽  
Safe Distance ◽  
Structure Interaction ◽  
Parachute Inflation ◽  
Good Agreement

Abstract In order to study the safe distance between twin-parachute during their inflation process for fighter ejection escape, the fighter was equipped with two canopies and two seats, two types of parachute were used to numerically simulate their inflation process, respectively. One of them is C-9, the other a slot-parachute (S-P). Their physical models were built, then the meshes inside and around both parachutes were generated for fluid-structure interaction (FSI) simulation. The penalty function and the arbitrary Lagrangian-Eulerian (ALE) method were employed in the FSI simulation. To validate the numerical model for FSI simulation, at first the single parachute of the twin-parachute was used for the FSI simulation, the predicted inflation times for both types of parachute were compared with the experimental data. The computed results are in good agreement with experimental data. As a result, the inflation times were predicted with twin-parachute for both kinds of parachute. On the basis of the locations of ejected seats after the separation of seat and pilot, the initial locations and orientations of twin-parachute were also obtained. The numerical simulations for both kinds of parachute were performed by the FSI method, respectively. Our results illustrate that when the interval time for two seats ejected is greater than 0.25s, two pilots attached the twin-parachute are safe, and the twin-parachute would not interfere each other. Moreover, our results also indicate that the FSI simulation for twin-parachute inflation process is feasible for engineering applications and have a great potential for wide use.

An Assessment of Primary Blast Injury in Human Brains: A Numerical Simulation

2007 ◽  
Author(s):  
Mahdi Sotudehchafi ◽  
Ghodrat Karami ◽  
Mariusz Ziejewski
Keyword(s):  
Numerical Simulation ◽  
Blast Wave ◽  
Human Head ◽  
Blast Injury ◽  
Element Formulation ◽  
Pressure Waves ◽  
Arbitrary Lagrangian Eulerian ◽  
Wave Interactions ◽  
Structure Interaction ◽  
Human Brains

Most blast-related injuries happen as a result of complex pressure waves generated by the explosion. In this paper, we model the explosion from detonation and examine the blast propagation in air using Arbitrary Lagrangian–Eulerian (ALE) finite element formulation. The results of the simulation agree well with those of physical data obtained from blast wave experiments. Such results set the circumstances necessary for an examination of brain injury exposed to such situations. Thus the model will be coupled with a Fluid/Structure Interaction (FSI) algorithm to implicitly examine the blast wave interactions with a human head and to study the creation of high regions of biomechanics pressure and stress gradients.

Towards a New Mathematical Model for Investigating Course Stability and Maneuvering Motions of Sailing Yachts

2016 ◽  
Author(s):  
Manolis Angelou ◽  
Kostas J. Spyrou
Keyword(s):  
Mathematical Model ◽  
Aerodynamic Force ◽  
Wave Forces ◽  
Element Formulation ◽  
Wave Excitation ◽  
Structure Interaction ◽  
Stage Of Development ◽  
Course Stability ◽  
Shell Finite Element ◽  
Interaction Problem

In order to create capability for analyzing course instabilities of sailing yachts in waves, the authors are at an advanced stage of development of a mathematical model comprised of two major components: an aerodynamic, focused on the calculation of the forces on the sails, taking into account the variation of their shape under wind flow; and a hydrodynamic one, handling the motion of the hull with its appendages in water. Regarding the first part, sails provide the aerodynamic force necessary for propulsion. But being very thin, they have their shape adapted according to the locally developing pressures. Thus, the flying shape of a sail in real sailing conditions differs from its design shape and it is basically unknown. The authors have tackled the fluid-structure interaction problem of the sails using a 3d approach where the aerodynamic component of the model involves the application of the steady form of the Lifting Surface Theory, in order to obtain the force and moment coefficients, while the deformed shape of each sail is obtained using a relatively simple Shell Finite Element formulation. The hydrodynamic part consists of modeling hull reaction, hydrostatic and wave forces. A Potential Flow Boundary Element Method is used to calculate the Side Forces and Added Mass of the hull and its appendages. The Side Forces are then incorporated into an approximation method to calculate Hull Reaction terms. The calculation of resistance is performed using a formulation available in the literature. The wave excitation is limited to the calculation of Froude - Krylov forces.

Predictive Capability of a 2D FNPF Fluid-Structure Interaction Model

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Solomon C. Yim ◽  
Huan Lin ◽  
David C. Robinson ◽  
Katsuji Tanizawa
Keyword(s):  
Free Surface ◽  
Numerical Models ◽  
Fluid Structure Interaction ◽  
Nonlinear Behavior ◽  
Degree Of Freedom ◽  
Surface Boundary ◽  
Predictive Capability ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Highly Nonlinear

The predictive capability of two-dimensional (2D) fully-nonlinear-potential-flow (FNPF) models of an experimental submerged moored sphere system subjected to waves is examined in this study. The experimental system considered includes both single-degree-of-freedom (SDOF) surge-only and two-degree-of-freedom (2DOF) surge-heave coupled motions, with main sources of nonlinearity from free surface boundary, large geometry, and coupled fluid-structure interaction. The FNPF models that track the nonlinear free-surface boundary exactly hence can accurately model highly nonlinear (nonbreaking) waves. To examine the predictive capability of the approximate 2D models and keep the computational effort manageable, the structural sphere is converted to an equivalent 2D cylinder. Fluid-structure interaction is coupled through an implicit boundary condition enforcing the instantaneous dynamic equilibrium between the fluid and the structure. The numerical models are first calibrated using free-vibration test results and then employed to investigate the wave-excited experimental responses via comparisons of time history and frequency response diagrams. Under monochromatic wave excitations, both SDOF and 2DOF models exhibit complex nonlinear experimental responses including coexistence, harmonics, subharmonics, and superharmonics. It is found that the numerical models can predict the general qualitative nonlinear behavior, harmonic and subharmonic responses as well as bifurcation structure. However, the predictive capability of the models deteriorates for superharmonic resonance possibly due to three-dimensional (3D) effects including diffraction and reflection. To accurately predict the nonlinear behavior of moored sphere motions in the highly sensitive response region, it is recommended that the more computationally intensive 3D numerical models be employed.

Computational Simulation of Free Surface Flows Using Stabilized Edge-Based Finite Element Method

2010 ◽  
Author(s):  
Renato N. Elias ◽  
Milton A. Gonc¸alves ◽  
Alvaro L. G. A. Coutinho ◽  
Paulo T. T. Esperanc¸a ◽  
Marcos A. D. Martins ◽  
...  
Keyword(s):  
Finite Element ◽  
Free Surface ◽  
Computational Simulation ◽  
Free Surface Flows ◽  
Element Formulation ◽  
Normal Velocity ◽  
Offshore Platforms ◽  
Arbitrary Lagrangian Eulerian ◽  
Parallel Edge ◽  
Edge Based

Flows involving waves and free-surfaces occur in several problems in hydrodynamics, such as sloshing in tanks, waves breaking in ship and motions of offshore platforms. The computation of such wave problems is challenging since the water/air interface (or free-surface) commonly present merging, fragmentation and cusps, leading to the use of interface capturing Arbitrary Lagrangian-Eulerian (ALE) approaches. In such methods the interface between the two fluids is captured by the use of a marking function which is transported in a flow field. In this work we simulate these problems with a 3D incompressible SUPG/PSPG parallel edge-based finite element flow solver associated to the Volume-of-Fluid (VOF) method [1]. The hyperbolic equation for the transport of the marking function is also solved by a fully implicit parallel edge-based SUPG finite element formulation. Global mass conservation is enforced adding or removing mass proportionally to the absolute value of the normal velocity at the interface. The performance and accuracy of the proposed solution method is tested in the simulation of pulse wave and the interaction of a fixed square cylinder with a progressive wave.

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