Fluid Structure Interaction Parachute Benchmark Models in LS-DYNA

In recent years, computational simulations have emerged as valuable tools for the evaluation of atherosclerosis progression in coronary anatomies, although only a few studies have utilized more realistic Fluid-Structure Interaction (FSI) simulations. This work aims to compare the results of Computational Fluid Dynamics (CFD), Structural Finite Element Analysis (structural FEA) and FSI simulations in order to assess differences in plaque progression indices estimation. We performed structural FEA, CFD and FSI on five patient-specific epicardial coronary anatomies using the commercial software LS-Dyna. To account for the vessel pre-stress, the zero-pressure configuration was calculated for each anatomy with an inverse elastostatic algorithm. CFD, structural FEA and FSI simulations were performed applying boundary conditions based on physiological values. The comparison between structural FEA and FSI showed similar stress distribution and vessel expansions, with differences found only in the distal parts of the coronaries, where pressure reduction due to pressure loss affects the vessel walls. The elastic walls of the coronaries impact blood flow, resulting in a more disturbed flow. However, time averaged wall shear stress (TAWSS) and oscillatory shear index (OSI) distributions are similar across each coronary between CFD and FSI; TAWSS is slightly higher in CFD while OSI peaks are higher in FSI. In conclusion, given the significantly higher computational costs of FSI, we believe that CFD and structural FEA offer a more practical and cost-effective approach, providing results comparable to those of FSI, making them preferable options.

The present paper is concerned with the problem of modeling dynamic test. The study focuses on the fluid-structure interaction (FSI) in spent fuel pool, which is filled with liquid and spent fuel components. Through the comparison of the results of numerical analysis (Based on LS-DYNA) and modeling test, such as the sloshing wave amplitude; the displacement & inclination angle of the storage racks; pressure exerted on the plate of racks and the walls of the pool were obtained, This paper evaluates the seismic performance and the safety margin of the structure, and also provides the surface pressure input for the design of storage racks. The phenomena of liquid sloshing in spent fuel pool presents a great interest for civil and nuclear engineering, the dynamic effects of sloshing in spent fuel pool could affect the plates of storage racks and the wall of spent fuel pool during strong earthquakes. Study of sloshing in spent fuel pool is proved challenging due to the presence of strong flow interactions with storage racks in the pool. The movement effect caused by the sloshing load of liquid is the primary reason for the problem to become more complicated. In this study, two models were created, one is scaled model for shacking table test, another is a numerical model utilize finite element analysis code LS-DYNA. LS-DYNA command *CONSTRAINED_LAGRANGE_IN_SOLID was used to simulate the interaction between solid material and fluid material (fluid-solid coupling effect). Considering the fluid-solid coupling effect between solid and fluid, ALE (Arbitrary Lagrange Euler) element and Lagrange element were used to simulate fluid material and solid material respectively based on their different characters in the numerical model. Using the three spatial components of artificial time histories generated from the design response spectra. The following parameters should be paid attention to in both the scaled model shacking table test and the numerical simulation of time history analysis: The relative displacement between the structure of the spent fuel pool and storage racks; inclination angle of the storage racks; pressure exerted on the plate of storage racks and the wall of pool and the sloshing wave amplitude. In this paper, the integrated pressure represented by the impulsive hydrodynamic pressure on the plate of storage racks between the shacking table test model and the numerical model were calculated and compared. The analytical parameters of numerical model were corrected to make the numerical model result consistent with modeling test result. In this way, a more reasonable numerical model is obtained.

The truss spar is a proven floating production platform for a range of deepwater offshore oil and gas developments. From wells and manifolds on the seabed, catenary risers and umbilicals are routed from the keel of the platform to its topsides through steel pull tubes. Depending on the field architecture there may be a large number of pull tubes arranged within the truss in a complex, tightly-spaced array, where the spacing varies with elevation. Individual tubes may be fitted with strakes or other devices intended to suppress flow-induced vibrations. Fatigue of these tubes is an important consideration that influences their own design as well as riser and hull design. While relatively simple, semi-empirical programs do exist to analyze the fatigue due to vortex-induced vibrations (VIV) of isolated tubes in steady flows, none are generally available to analyze the complex fluid-structure interaction associated with this scenario. Existing models do not include the degradation of strake performance as a vibration suppressor in an arrayed, rather than isolated, configuration; buffeting of tubes in the turbulent wakes of the truss members and neighboring tubes; and, coupled fluid-tube interaction. Coupled computational fluid-structure inter-action (FSI) techniques - finite element (FE) solutions of a structural model coupled iteratively with computational fluid dynamics (CFD) solutions of a fluid model until convergence - are becoming progressively more feasible for addressing this type of problem as computing speeds and capacities continue to increase. This paper will demonstrate how one such computational coupled FSI has been used to deliver useful fatigue results in support of the design of a 35-tube array in a truss spar. It will also describe some key insights into the force-response mechanisms that would not have been discoverable via other analytical methods. Finally, it will make some qualitative comparisons to phenomena observed in physical model tests.

This paper provides a review of the space–time (ST) and Arbitrary Lagrangian–Eulerian (ALE) techniques developed by the first three authors' research teams for patient-specific cardiovascular fluid mechanics modeling, including fluid–structure interaction (FSI). The core methods are the ALE-based variational multiscale (ALE-VMS) method, the Deforming-Spatial-Domain/Stabilized ST formulation, and the stabilized ST FSI technique. A good number of special techniques targeting cardiovascular fluid mechanics have been developed to be used with the core methods. These include: (i) arterial-surface extraction and boundary condition techniques, (ii) techniques for using variable arterial wall thickness, (iii) methods for calculating an estimated zero-pressure arterial geometry, (iv) techniques for prestressing of the blood vessel wall, (v) mesh generation techniques for building layers of refined fluid mechanics mesh near the arterial walls, (vi) a special mapping technique for specifying the velocity profile at an inflow boundary with non-circular shape, (vii) a scaling technique for specifying a more realistic volumetric flow rate, (viii) techniques for the projection of fluid–structure interface stresses, (ix) a recipe for pre-FSI computations that improve the convergence of the FSI computations, (x) the Sequentially-Coupled Arterial FSI technique and its multiscale versions, (xi) techniques for calculation of the wall shear stress (WSS) and oscillatory shear index (OSI), (xii) methods for stent modeling and mesh generation, (xiii) methods for calculation of the particle residence time, and (xiv) methods for an estimated element-based zero-stress state for the artery. Here we provide an overview of the special techniques for WSS and OSI calculations, stent modeling and mesh generation, and calculation of the residence time with application to pulsatile ventricular assist device (PVAD). We provide references for some of the other special techniques. With results from earlier computations, we show how these core and special techniques work.

Study of flow characteristics of human airways using Fluid-Structure Interaction (FSI) analysis is very important in the context of prognosis, diagnostic and treatment of respiratory diseases. The present study is focused on effect of elasticity on the respiratory wall during inhalation. Airflow in Computed Tomography (CT) scan model with rigid and compliant airway walls is studied. FSI technique is used to simulate the airflow in the model. The comparison for the two different respiratory models (rigid and compliant) shows that FSI technique brings out more realistic results as compared to Computational Fluid Dynamics (CFD) analysis. It is found that respiratory wall elasticity affects the different flow parameters (pressure, wall shear stress, etc.) at different location of the model. Wall shear stress (WSS) and airway pressure were decreased due to flexibility effect of the airway wall. This will help medical practitioners to correlate the clinical assessment with this FSI results.

Failure pressure calculation of fracturing well based on fluid-structure interaction

A novel coupled Riemann SPH–RKPM model for the simulation of weakly compressible fluid–structure interaction problems

Validation of numerical models for seismic fluid-structure-interaction analysis of nuclear, safety-related equipment

The patch material and dimension are two important factors which might affect the surgical outcomes after the aortic arch coarctation repair surgery. To quantity their acute impacts on the biomechanical environment of the repaired aortic arch, an aortic arch model was constructed and the fluid-structure interaction (FSI) technique was utilized to characterize its hemodynamics and wall mechanics. Three different patch materials were considered including pulmonary artery, ECM CorMatrix and Polytetrafluoroethylene (PTFE). The induced wall shear stress, distribution of flow patterns, and von-Mises stress on arterial wall were compared. Results showed that ECM CorMatrix patch had better performance Two different patch dimension (large v.s small) using CorMatrix patch were compared and the relatively smaller patch demonstrated a better hemodynamics than the larger one. No significant difference in terms of wall stress was observed between the different patch sizes.

<div class="section abstract"><div class="htmlview paragraph">This study deals with the mitigation of the vibration of the structure using a compound mass liquid column damper (MLCD). To study the damping efficiency of the MLCD, the mathematical model of the single degree of freedom structure integrated with MLCD including the damping due to the moving mass in the horizontal portion of the damper is derived. The equivalent-damping factor of the MLCD is determined by simulating the interaction between the moving mass and the liquid using the fluid-structure interaction (FSI) technique. A 3D FSI model is solved numerically using the ANSYS Workbench-CFX package. The global search optimization algorithm is applied to find the optimum tuning frequency and the optimum mass diameter ratio over a wide range of mass ratio and excitation amplitude. The optimization issue is solved with considering the limits of the maximum displacement of the liquid and the mass. Design charts for the optimum parameters and their corresponding performance index for the mass ratio from 3% to 10% and excitation intensity from 0.1% to 2% are presented. The results obtained show that the efficiency of the MTCD to mitigate the structure vibration is higher than that for the traditional liquid damper especially for excitation intensity factor over than 1 %. The efficiency of the MLCD to reduce the structure vibration reached about 95% using the proposed optimum parameters.</div></div>

Innovative computational modal analysis of a marine propeller

Vascular compliance is considered both a cause and a consequence of cardiovascular disease and a significant factor in the mid- and long-term patency of vascular grafts. However, the biomechanical effects of localised changes in compliance cannot be satisfactorily studied with the available medical imaging technologies or surgical simulation materials. To address this unmet need, we developed a coupled silico-vitro platform which allows for the validation of numerical fluid-structure interaction results as a numerical model and physical prototype. This numerical one-way and two-way fluid-structure interaction study is based on a three-dimensional computer model of an idealised femoral artery which is validated against patient measurements derived from the literature. The numerical results are then compared with experimental values collected from compliant arterial phantoms via direct pressurisation and ring tensile testing. Phantoms within a compliance range of 1.4–68.0%/100 mmHg were fabricated via additive manufacturing and silicone casting, then mechanically characterised via ring tensile testing and optical analysis under direct pressurisation with moderately statistically significant differences in measured compliance ranging between 10 and 20% for the two methods. One-way fluid-structure interaction coupling underestimated arterial wall compliance by up to 14.7% compared with two-way coupled models. Overall, Solaris™ (Smooth-On) matched the compliance range of the numerical and in vivo patient models most closely out of the tested silicone materials. Our approach is promising for vascular applications where mechanical compliance is especially important, such as the study of diseases which commonly affect arterial wall stiffness, such as atherosclerosis, and the model-based design, surgical training, and optimisation of vascular prostheses.

This study describes a simple design for a single active element sinusoidal oscillator with a quadrature signal. A current conveyor transconductance amplifier (CCTA), a single resistor, and two grounded capacitors are used in the first circuit. The second circuit is improved by using a current-controlled current conveyor transconductance amplifier (CCCCTA) and two grounded capacitors without a passive resistor, which means the grounded capacitor is suitably implemented for the IC fabrication. The oscillation condition and frequency of both circuits can be controlled using the same method that concurrently adjusts the DC bias current and the resistance as well as the oscillation frequency can be independently adjusted by capacitances. The CCTA is achieved by cascading the integrated circuits (IC) AD844 and LM13700, made by Analog Devices Corporation and Texas Instruments, respectively, which are available for commercial purchase. The sinusoidal quadrature signals in the time-domain and frequency-domain can be shown with computer simulations and the results of experiments. The Monte Carlo Analysis is also utilized to examine the oscillation frequency with the influence of passive element tolerance errors. The predicted oscillation frequency has a standard variation of about 20.04 kHz, with a maximum frequency of approximately 346.89 kHz and a minimum frequency of approximately 259.09 kHz. In addition, the mean and median frequencies are 296.10 and 293.98 kHz, respectively. The results of this study indicate that computer simulation and experiment are similar to a theoretical analysis, making them suiTable for use in the teaching of electrical and electronic engineering

: This document summarizes research done during the period June 14, 1989 through December 14, 1991 on a project aimed at the development of advanced computational methods for modeling multiscale fluid-structure interaction phenomena. The major thrust of the work reported is the development of the component parts of a new family of computational schemes that could be used to study large-scale problems in fluid-structure interaction. The overall theme of the project was the optimization of the computational process through the development of new adaptive techniques, data structures, a posteriori error estimates, and high-order solvers. The premise behind studying these types of high-order methods is that, with proper data structures, they could lead to exponential rates of convergence and thereby allow one to numerically solve very large problems, with features covering many different physical scales, using many fewer degrees of freedom than that required by conventional methods. In this spirit, the project was an ambitious one for it involved developing not only new adaptive algorithms for simulating the motion of elastic structures, but also techniques for fluid structure interaction and for modeling various regimes of incompressible viscous flows. Presumably, these methods could also be used to model the transition to turbulence and ultimately turbulent boundary layers on compliant surfaces.

Fluid–structure interaction is analyzed using 1D and 3D computational models and results from an experimental facility, where transient events are induced. The water-hammer phenomenon is modelled by a 1D model based on the method of characteristics and the COMSOL Multiphysics 4.3b, which uses finite element method to study the fluid structural interaction involved in a long pressurized pipe system with curves, expansion joints, anchor and support blocks and different rheological behaviour of the pipe material. Comparisons are made between the experimental data and the two numerical models, where the type of response of each model was enhanced, as well as the ability of each model to simulate real conditions.