Fluid-structure Interaction Analysis Research Articles

Structural design optimization of vibration lures based on CAE

Lure fishing, a sports-like game using artificial lures as baits, has been popular around the world. In the present work, to enhance the underwater vibration behavior of vibration lures, we carry out structural design optimization of vibration lures based on computer aided engineering (CAE). At first, we create the finite element model of a vibration lure by a 3D scanner and perform weak coupled fluid-structure interaction (FSI) analysis of the vibration lure using finite element method. Then, according to the simulation results, we optimize the eye position (i.e., the knot position between fishing line and lure) and the positions of the weight placed in the lower part of the lure to obtain its largest fluid induced frequency.

Elmerによる胸部大動脈解離を対象とした流体-構造連成解析

The aorta is an important artery that carries the blood pumped out of the heart and mainly consists of the ascending aorta (Ascending Aorta, AAo), the aortic arch (Arch of Aorta), and the descending aorta (Descending Aorta, DAo). Aortic dissection is a condition in which the blood leaks through a tear formed on the intimal surface of the aorta and causes the vessel wall to tear in the longitudinal direction. The effect of the dissection spreads to not only aorta but also other parts of the body, and may lead to aneurysms and ruptures. In this study, the effects of blood flow on the aortic vessel wall was examined by performing a fluid-structure interaction (FSI) analysis method using an opensource multiphysics software “Elmer”. In the analysis, pulsating flow was given as the boundary condition between the inlet and outlet of the aorta models. As a result, four parameters of flow velocity and line, pressure, displacement of the vessel wall, wall shear stress (WSS) of an aortic dissection model were calculated and visualized, and compared with a healthy aortic model.

Fluid–Structure Interaction Analysis for Deformation of Blood Vessels Considering Mechanical Constraints of Surrounding Tissues

Fluid–Structure Interaction Analysis for Deformation of Blood Vessels Considering Mechanical Constraints of Surrounding Tissues

Wind-structure interaction analysis of empty cylindrical silos for various slenderness ratio

Wind is the flow of air within the earth’s atmosphere, which affects any structure greatly. Studies on the effect of wind loading on shell structures is an important field of structural research. Many shell structures, such as, chimneys, silos, tanks etc. are an integral part of the advancement of the industry and agriculture. Such shell structures are vulnerable against aerodynamic excitation and can be subjected to structural failure due to vortex-induced vibration, ovalling, buckling, rupture, over-turning etc. The present study focuses on the static fluid–structure interaction analysis to assess the wind pressure and wind-induced deformation of cylindrical silo shells. Cylindrical silos are a type of shell structure for storing granular materials, such as grains, wheat, cement, coal, fly-ash etc. Cylindrical silos very much susceptible to radial deformation and buckling failure under wind loading in empty state. In the present study the authors have conducted the wind-structure interaction studies on intermediate to tall (slenderness ratio range: 1.5 to 4.0) cylindrical silo shells for terrain category 2, as per IS-875: part 3, 2015. The silos are flat topped with uniform thickness and fixed at the base, free at the top. The logarithmic law is used to simulate wind velocity profile. The circumferential mean wind pressure coefficient distribution for each silo, is calculated and compared with Indian standard. This study is conducted for smooth flow with very low turbulence intensity for simplicity. This study exhibits that, with the increase in slenderness ratio from 1.5 to 4.0, the magnitude of negative pressure coefficients decreases, however no significant increase can be seen for positive pressure coefficients. The sway of the silos increases with the increment in slenderness ratio. The radial deformation is dominant in the intermediate portion and the nature of deformation is typical for each silo. Based on the nature of radial deformation the critical locations can be identified, which need to be strengthened to resist wind-induced deformation. It is also seen that the presence of flat roof provides significant strengthening at the top of the silos against wind-induced radial deformation.

Two-way Fluid Structure Interaction Analysis of Single Pad Externally Adjustable Fluid Film Bearing

Two-way Fluid Structure Interaction Analysis of Single Pad Externally Adjustable Fluid Film Bearing

Investigation of optimal shape/structural design of fishing lures

In this study, we introduce the idea, the present research state, and the prospects for the optimal shape/structure design of fishing lures based on CAE. Since a fishing lure appeals its underwater motion or behavior, e.g., fluid-induced vibration, rotation. sound, flashing light, as baits to catch fish, we mainly investigate the vibration behavior of fishing lures and perform their shape/structure optimization for lure design. Up to now, only considering water pressure as external force on vibration lures, we have developed a gradient-based shape optimization method for enhancing their vibration behavior. Recently, considering the real analytical condition, we reproduced flow-induced vibration of fishing lures by weakly coupled fluid-structural interaction analysis and optimized their optimal structures using the Box-Behnken design. In the future, we aim to develop a gradient-based shape/structure optimization method for lure design that can make lure fishing more efficient and more interesting.

Fluid-structure interaction analysis of heat exchanger with torsional flow in the shell side

Fluid-structure interaction analysis of heat exchanger with torsional flow in the shell side

복합하중을 받는 도로시설물의 구조안전성 평가를 위한 유한요소해석 방법의 적용

Since structures such as road facilities generally operate under various load conditions, it is necessary to evaluate the structural strength for the complex load in the design process of the structure. This study introduces the structural strength assessment approach of the structures by applying finite element analysis (FEA) methods. The assessment methods were considered in combination for structural response by wind load, vibration load and fatigue life evaluation. To evaluate the structural response by the wind load, 1-way Fluid structure interaction (FSI) analysis method combined with computational fluid dynamics (CFD) analysis was applied. Furthermore, the strength assessment for the vibration load was evaluated by modal analysis, harmonic response and spectral analysis about vibration and seismic load condition. Finally, to ensure the proposed method two typical types of traffic facilities were applied: wireless and wired structure of road facilities. In FEA results, the structural performance due to wind load was similarly evaluated. However, for vibration performance, it has been confirmed that the wireless type relatively has good performance. Through these results, this paper reviews the need for the FEA applications and introduces the proposed approach and examples.

Experimental and Numerical Studies on Fluid-Structure Interaction for Underwater Drop of a Stone-Breaking Crusher

There are many methods for crushing seabed rock such as a using a free-falling crusher, blasting, and chemical liquid expansion. Blasting and chemical liquid expansion can lead to environmental destruction, noise pollution, and civil complaints. Therefore, a free-falling crusher is generally recommended for use. Understanding the characteristics of a crusher in water and the impact force on the ground is helpful for designing a crusher and dredge work. In this study, drop tests of 50 and 70 ton crusher models that were scaled down by 15 times were investigated. The tests were conducted in a water basin by the Research Institute of Medium and Small Shipbuilding (RIMS) in Korea. Four water depths were considered with different falling locations: water surface and air. Moreover, a numerical study on Fluid-Structure Interaction (FSI) analysis for a free-falling crusher was conducted by applying the Arbitrary Lagrangian-Eulerian (ALE) element and the Grüneisen Equation of State (EoS) to fluid models. The crusher and ground were modeled as Lagrangian elements to estimate the impact force on the ground. Before comparing the crusher model, a free-falling sphere model was used to develop FSI technologies by comparing past Computational Fluid Dynamics (CFD) and experimental results. Moreover, the recommended mesh size and fluid domain for FSI analysis are provided to achieve good results via convergence tests. Comparison between experimental and numerical methods demonstrated a similar tendency such that impact force increased at a higher depth. Certain numerical results agree with average values of experimental results; however, multiple numerical cases exhibit a moderate difference. This is because of angular rotation between the crusher and ground when the crusher hits the ground during experiments.

Impact of the Thruster Jet Flow of Ultra-large Container Ships on the Stability of Quay Walls

As the size of ships increases, the size and output power of their thrusters also increase. When a large ship berths or unberths, the jet flow produced from its thruster has an adverse effect on the stability of quay walls. In this study, we conducted a numerical analysis to examine the impact of the thruster jet flow of a 30,000 TEU container ship, which is expected to be built in the near future, on the stability of a quay wall. In the numerical simulation, we used the fluid–structure interaction analysis technique of LS-DYNA, which is calculated by the overlapping capability using an arbitrary Lagrangian Eulerian formulation and Euler–Lagrange coupling algorithm with an explicit finite element method. As the ship approached the quay wall and the vertical position of the thruster approached the mound of the quay wall, the jet flow directly affected the foot-protection blocks and armor stones. The movement and separation of the foot-protection blocks and armor stones were confirmed in the area affected directly by the thruster jet flow of the container ship. Therefore, the thruster jet flows of ultra-large ships must be considered when planning and designing ports. In addition, the stability of existing port structures must be evaluated.

Fluid-Structure Interaction Analysis of Aircraft Hydraulic Pipe with Complex Constraints Based on Discrete Time Transfer Matrix Method

Fluid-structure interaction (FSI) is prevalent in aircraft hydraulic pipes due to high-pressure fluid pulsation, complex pipe path routing and boundary constraints, which pose a serious threat to the safety and reliability of the aircraft hydraulic system. This paper focuses on the FSI response of aircraft hydraulic pipes with complex constraints. A comprehensive fourteen-equation model for describing the FSI of pipe conveying fluid with wide pressure and Reynolds number range is proposed. The excitation models and complex boundary constraints of liquid-filled pipes are established. Moreover, based on the transfer matrix method (TMM), combined with the time discreteness and analytical integral method, a discrete time transfer matrix method (DTTMM) for solving the FSI fourteen-equation model in time domain is presented. Then, the numerical solution and experiment of an ARJ21-700 aircraft hydraulic pipe with complex constraints is carried out with four working conditions. The obtained results verify the correctness of the proposed model and solution method, and reveal the universal laws of the FSI response about aircraft hydraulic pipes, which can also provide theoretical and experimental references for modeling, solutions and verification in the FSI analysis of pipe conveying fluid.

Development of a coupling algorithm for fluid-structure interaction analysis of submerged aquaculture nets

A coupling algorithm between two open-source numerical toolboxes, i.e., OpenFOAM and Code_Aster, is implemented for fluid-structure interaction analysis of submerged nets. This algorithm is developed to handle the wake effects of thin, flexible and highly permeable structures with complex geometries. Compared to previous approaches, the present algorithm simplifies the procedures of the model preparation by removing additional data-fitting processes for porous coefficients, and improves the accuracy of structural responses by employing a fluid solver to calculate the flow field and a superior Screen model to calculate the hydrodynamic forces. The coupling algorithm is comprehensively described and validated with published experiments for both fixed and flexible nets. Different solidities, inflow angles, incoming velocities and dimensions of nets are also considered. The comparisons of flow velocity in the wake, deformation of flexible nets and drag force on the full-scale fish cage show that the numerical results obtained from the present coupling algorithm are in good agreement with published experimental data.

Fluid-structure interaction analysis of a lightweight sandwich composite structure for solar central receiver heliostats

Central tower concentrating solar power systems are moving to the forefront to become the technology of choice for generating renewable electricity, but their widespread implementation is limited by cost. Heliostats contribute almost 50% to the plant’s cost and are thus the most significant element in central tower systems. For both large and small-area heliostats, the drive elements demonstrate the largest cost element in these systems. While large-area heliostats (>100 m2) have proven offer the best economy compared to other sizes, they require high-torque drives due to the heavy steel-based support structure. Heliostat costs could be reduced by decreasing the support structure’s weight, avoiding large drive units and reducing energy consumption. However, the structure must be able to cope with the aerodynamic loads imposed upon them during operation. Although honeycomb sandwich composites have been widely used where high structural rigidity and low weight are desired, there is an absence of studies that rigorously investigated their suitability as the structure for heliostat mirror. Here, a fluid-structure interaction study investigated, for several loading conditions at various tilt and wind incidence angles, the aero-structural behavior characteristics of honeycomb sandwich composites used as a heliostat support structure. The honeycomb sandwich panel showed markedly different behavior characteristics at various operational conditions. The effect of tilt orientation on the sandwich panel’s maximum deflection and stresses became more pronounced as wind velocity increased above 10 m/s, and increasing wind incidence angle reduced their magnitudes at different rates. The supporting components and torque tube had a noticeable wind-shielding effect, causing pronounced changes in the deflection and stresses experienced by the heliostat. The worst operational condition was at a tilt angle of 30° with wind flow of 20 m/s at 0° to the heliostat surface. However, the heliostat maintained its structural integrity according to relevant optical and material failure standards.

Coupled computing for reactive hydrogen leakage phenomena with crack propagation in a pressure tank

This research focuses on reactive hydrogen leakage due to the fracturing of high-pressure hydrogen tanks to develop a coupled computing method that can simultaneously perform reactive fluid-structure interaction analyses. The integrated computational approach to reactive hydrogen leakage with combustion due to wall crack propagation was implemented using a hybrid of the coupled particle and Eulerian methods. This computational method provides valuable safety information for predicting crack propagation and hydrogen leakage with combustion reaction in pressure tanks as an essential part of assessing hydrogen as an energy vector. As a result, the effect of crack formation and wall boundary conditions on hydrogen turbulent diffusion and concentration distribution and the thermodynamic behavior of the chemical reaction were predicted computationally. It was found that a combustion reaction does not occur near the streamwise axis at the duct center because there is an excess of hydrogen fuel, which increases scalar dissipation, and that the combustion reaction separated into upper and lower regions as it proceeded.

Development of deep learning-based detection technology for vortex-induced vibration of a ship's propeller

Vortex-induced vibration (VIV) resulting lock-in phenomenon which is the vibration frequency of the structure immersed in a fluid is locked in its resonance frequencies within a flow speed range is a potential cause of vibration fatigue and/or singing of the propellers of large merchant ships. A deep learning-based indirect VIV detection algorithm that works by vibration measurement data of a hull structure instead of a propeller during the sea trial phase is proposed in this study. RPM-frequency representations of the vibration signal by stacking the vibration frequency spectrum relative to various propeller RPM's, so-called waterfall chart of 2-dimensional data like an image, are measured and fed into the proposed convolutional neural network (CNN) architecture for VIV detection i.e. VIV frequency and RPM range. To generate the large data set, artificial data looks real, for learning, a method based on the modal superposition method instead of time-consuming fluid-structure interaction analysis is proposed. 10k set data for training, 1k set for hyper-parameter tuning, and 1k set for the test were generated. After the training, it showed a diagnosis success rate of 82% for the test set. To test the proposed VIV detection algorithm, investigations were carried out in a laboratory on a small-scale ship propulsion system designed in such a way that the vortex shedding frequency and the underwater natural frequency match each other. The proposed VIV detection algorithm was tested using the structural vibration signals measured at stationary structures in the air instead of the rotating propeller immersed in water. Lastly, the validity of the proposed algorithm was tested using the structural vibration signal measured at the hull structure of a crude oil carrier in which a propeller singing occurred during her sea trial.

Finite element analysis in the modeling of the heart and aorta structures

Rationale: 3D modeling of various anatomical structures has recently become a separate area of topographical, anatomical, and biomechanical studies. Current in vivo visualization methods and quantitative analysis in silico allow to perform the precise modeling of these processes aimed at investigation into the pathophysiology of cardiovascular disorders, risk prediction, planning of surgical interventions and virtual refinement of their separate stages.Aim: To develop tools for elaboration, analysis and validation of personalized models of various structures of the heart and aortal arch taking into account their morphological characteristics.Materials and methods: We used the results of 14 computed tomography studies from randomized patients without any disease or anomaly of the heart, aortic valve and aortal bulb. The analysis and subsequent transformation of the images were done with Vidar DICOM Viewer, SolidWorks 2016, VMTKLab software. For the FSI modeling of the aortic arch based on the results of functional multiaxial computed (MAC) coronarography (a female patient of 55 years) we developed a personalized model of the ascending aorta and aortic arch at the beginning of the systole. Using HyperMesh software (Altair Engineering Inc., USA) we have built a network of finite element of the luminal area, adventitia, and aortic media. To model mechanical properties of the aortic structures we used an anisotropic hyperelastic material model by Holzapfel – Gasser – Ogden. Material modeling, choice of the limiting antecedents, and analysis of fluid-structure interaction were performed with Abaqus CAE 6.14 software (Simulia, Johnston, USA). Adaptive image meshing by Young was used to elaborate the finite element template of the left ventricle. The algorithm was realized within the IDE PyCharm software media in Python 3.7. The algorithm was realized based on the open-source libraries OpenCV, NumPy, Matplotlib, and SciPy.Results: The first stage of the development of the aortic valve model included the design of its virtual 3D template. Thereafter, a cohesive geometric model was elaborated. Subsequent stage of the work included the transformation of the aortic valve geometric model into the parametric one. This was done through the use of the “Equations” tool within the SolidWorks. No problems with geometry of the model during its deformation were identified. Aortic segment modeling was based on the data obtained by functional MAC coronarography. Based on this and on Inobitec Dicom Viewer software, we generated a multiplane reconstruction of the zone of interest including anatomical structure of the heart and aortic valve. With the resulting set of contours, we created a 3D model, which then was converted into a polygonal stereolithographic model. We developed an algorithm for adaptive meshing to elaborate a polygonal template capable of deformation that can be used for registration both with the net methods (B-Spline) and based on the image characteristics (homologous pixels). Conclusion: The resulting parametric 3D model of the aortic valve anatomical structures is capable of adequate transformation of its geometry under external factors. It can be used in simulators of endovascular cardiosurgical procedures.

Effect of plaque compositions on fractional flow reserve in a fluid-structure interaction analysis.

Coronary artery disease involves the reduction of blood flow to the myocardium due to atherosclerotic plaques. The findings of myocardial ischemia may indicate severe coronary stenosis, but many studies have demonstrated a mismatch between lumen stenosis and fractional flow reserve (FFR). Recently, some clinical studies have found that the composition of atherosclerotic plaques may be a potential missing link between stenosis and ischemia. To investigate the relationship between myocardial ischemia and plaque composition, we have developed and adopted a new fluid-structure interaction (FSI) patient-specific coronary plaque model, based on computed tomography angiography data, to assess the impact on FFR as a biomechanical indicator of ischemia. A total of 180 analyses have been performed in 3D-FSI coronary artery disease models based on plaque compositions, plaque location, and stenosis degree. Hemodynamic analysis of simulation results and comparisons with other methods has been conducted to validate our models. Our results have successfully verified that the different compositions of plaques have resulted in differences in the calculated FFR. The mean FFR values with lipid plaques are [Formula: see text] as compared to the mean FFR values in lesions with fibrous plaques [Formula: see text] and calcified plaques [Formula: see text]. Besides, FFR differences between the three different plaque compositions have been shown to increase as the diameter stenosis increased. Plaque composition affects vascular stiffness and vascular dilation ability, and thereby affects the stenosis degree, resulting in abnormal FFR leading to myocardial ischemia. This interrelationship can help to diagnose the cause of high-risk coronary artery disease, leading to myocardial ischemia.

Vessel structural stress mediates aortic media degeneration in bicuspid aortopathy: New insights based on patient-specific fluid-structure interaction analysis

This study aimed to assess the relationship between local mechanical stimuli and regional aortic tissue degeneration using fluid–structure interaction (FSI) analysis in patients with bicuspid aortic valve (BAV) disease. Nine patients underwent ascending aortic replacement were recruited. Tissues were collected to evaluate the pathology features in four regions, greater curvature (GC-region), posterior (P-region), anterior (A-region), and lesser curvature (LC-region). FSI analysis was performed to quantify vessel structural stress (VSS) and flow-induced parameters, including wall shear stress (WSS), oscillatory shear index (OSI), and particle relative residence time (RRT). The correlation between these biomechanical metrics and tissue degeneration was analyzed. Elastin in the medial layer and media thickness were thinnest and the gap between fibers was biggest in the GC-region, followed by the P-region and A-region, while the elastin and media thickness were thickest and the gap smallest in the LC-region. The collagen deposition followed a pattern with the biggest in the GC-region and least in the LC-region. There is a strong negative correlation between mean or peak VSS and elastin thickness in the arterial wall in the GC-region (r = -0.917; p = 0.001 and r = -0.899; p = 0.001), A-region (r = -0.748; p = 0.020 and r = -0.700; p = 0.036) and P-region (r = -0.773; p = 0.014 and r = -0.769; p = 0.015), and between mean VSS and fiber distance in the A-region (r = -0.702, p = 0.035). Moreover, strong negative correlation between mean or peak VSS and media thickness was also observed. No correlation was found between WSS, OSI, and RRT and aortic tissue degeneration in these four regions. These findings indicate that increased VSS correlated with local elastin degradation and aortic media degeneration, implying that it could be a potential biomechanical parameter for a refined risk stratification for patients with BAV.

A Coupled Two-Way Fluid–Structure Interaction Analysis for the Dynamics of a Partially Confined Cantilevered Pipe Under Simultaneous Internal and External Axial Flow in Opposite Directions

Abstract This paper presents the results of a coupled two-way fluid–structure interaction (FSI) analysis of a slender flexible vertical cantilevered pipe hanging concentrically within a shorter rigid tube forming an annulus. The pipe is subjected to internal and annular flows simultaneously. This system has applications in brine production and salt-cavern hydrocarbon storage. In this study, the fluid–structure problem is solved with a finite volume based computational fluid dynamics (CFD) code for the fluid domain coupled to a finite element based computational solid mechanics code for the structural domain. The numerical results obtained for the free-end displacement of the central pipe versus the annular/internal flow velocity ratio Uo/Ui are presented and compared with those obtained from experiment. The capability of the numerical model to predict the onset of the experimentally observed flutter instability in the system is also examined. This study provides a better insight into the dynamics of the system.

Behavior of Multiple Blocks Mounted Underwater Using Fluid-Structure Interaction and Contact Analysis

Kang, C.; Lee, W.D.; Kim, T.; Lee, T.K., and Hong, S., 2021. Behavior of multiple blocks mounted underwater using fluid-structure interaction and contact analysis. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 589–593. Coconut Creek (Florida), ISSN 0749-0208. This study discusses a method for estimating the structural stability of a coastal concrete structure with an emphasis on sliding and overturning due to tidal current or waves. Because of the complexity of fluid flow behavior, a coastal structure was assumed to be a rigid body for structural safety reviews. Namely, the safety reviews assume the stress and strain of a structure insignificant and focus only on the fluid analysis. However, a structural analysis should be considered especially if the structure is not of single, large block construction, such as artificial reef blocks, which are stacked on each other. An artificial reef is normally composed of small concrete blocks stacked together. A section of each block is relatively small and interacts with each other blocks. Macro issues, such as sliding and over-turning as well as micro issues such as stress concentration and contact between blocks must be considered. This study emphasizes the microstructural point of view, such as the stress and strain of each artificial block and the interaction between blocks. ABAQUS 2D fluid-structure interaction analysis was performed where the simultaneous analysis was completed using computational flow dynamics; in addition, the performance of a structural analysis using finite element modeling.