Structure Interaction Research Articles

Energy balance during Bragg wave resonance by submerged porous breakwaters through a mixture theory-based δ-LES-SPH model

This paper presents a numerical analysis of the time behaviors of mechanical and internal fluid energies during the Bragg wave resonance induced by two-arrayed trapezoidal submerged porous breakwaters based on a reformatted δ-LES-SPH model (Di Mascio et al., 2017). In the present work, a mixture theory is introduced into the δ-LES-SPH model by reformulating the governing equations with the incorporation of a volume fraction. In this approach, the viscous and diffusive terms are also modified by the volume fraction. The energy equation is then written for the presented model highlighting the presence of two additional components compared with the classical δ-LES-SPH formulation: one coming from the fluid compression and another one due to the dissipation both induced by the interaction of the porous structure with the fluid phase. The numerical results are validated by available experimental data for a gravity-driven mass flow passing through a porous dam case and two Bragg wave resonance by two-arrayed submerged trapezoidal porous breakwaters cases. A numerical analysis is then conducted on Bragg wave resonance by two-arrayed trapezoidal porous breakwaters, by investigating the effects of the distance between the two breakwaters and their porosity. Interesting insights about the type and magnitude of dissipation occurring during the wave-structure interaction are captured by analyzing the time evolutions of each energy component.

Fabrication of novel chitosan decorated reduced graphene oxide/cobalt oxide hybrid nanocomposite electrode material for supercapacitor applications

Supercapacitors are considered efficient electrochemical energy storage devices due to their high-power density, long cycling stability, and quick charge–discharge rates. Despite exhibiting high power density and cycling stability, the electrode materials are toxic and non-degradable, continuously affecting the environment. Biopolymers are a suitable alternative to conventional electrode materials since they possess interesting properties such as unique structure, biodegradability, abundant availability, and efficient interaction with other materials. This study aims to synthesize chitosan (CS) based nanocomposites, namely CS-rGO, CS-Co3O4, and CS-rGO-Co3O4 hybrid nanocomposites by an effective simple strategy method. XRD results show well-intensified peaks confirming the formation of nanocomposites. SEM and HR-TEM analysis indicates the cobalt oxide nanoparticles diffused in the sheet-like structure of CS-rGO which is evident for the porous nature of the CS-rGO-Co3O4 hybrid nanocomposite. A novel CS-rGO-Co3O4 hybrid nanocomposite showed surpassing electrochemical performance compared to other synthesized binary composites. The hybrid composite exhibited a high specific capacitance of 361.31 Fg−1 with an electroactive surface area of 136.880 m2g−1. In GCD, the hybrid composite demonstrates a 70 % capacitance retention and 99 % Coulombic efficiency after 10,000 cycles. An asymmetric hybrid supercapacitor is assembled using CS-rGO-Co3O4 nanocomposite as an anode and activated carbon as a cathode. The assembled AHS device delivers a high specific capacitance of 75.7 Fg−1 at 0.5 Ag−1. The energy density of the CS-rGO-Co3O4 hybrid nanocomposite is 23.6 WhKg−1 and the power density is 734.15 WKg−1. Hence, our research provides valuable insights for developing high-performance supercapacitor electrodes.

Targeting adhesion G protein-coupled receptors. Current status and future perspectives.

G protein-coupled receptors (GPCRs) orchestrate many physiological functions and are a crucial target in drug discovery. Adhesion GPCRs (aGPCRs), the second largest family within this superfamily, are promising yet underexplored targets for treating various diseases, including obesity, psychiatric disorders, and cancer. However, the receptors' unique and complex structure and miscellaneous interactions complicate comprehensive pharmacological studies. Despite recent progress in determining structures and elucidation of the activation mechanism, the function of many receptors remains to be determined. This review consolidates current knowledge on aGPCR ligands, focusing on small molecule orthosteric ligands and allosteric modulators identified for the ADGRGs subfamily (subfamily VIII), (GPR56/ADGRG1, GPR64/ADGRG2, GPR97/ADGRG3, GPR114/ADGRG5, GPR126/ADGRG6, and GPR128/ADGRG7). We discuss challenges in hit identification, target validation, and drug discovery, highlighting molecular compositions and recent structural breakthroughs. ADGRG ligands can offer new insights into aGPCR modulation and have significant potential for novel therapeutic interventions targeting various diseases.

Experimental decomposition of nonlinear hydrodynamic loads and hydroelastic responses in wave–structure interactions of monopile wind turbines

This study explores the nonlinear effects of hydrodynamic loads and hydroelastic responses in monopile-supported offshore wind turbines, with a focus on their harmonic structures. High-quality experimental data were collected in a shallow water basin across various irregular waves. Their harmonic components up to the fourth order were successfully isolated using a novel four-phase decomposition technique, which effectively extracts harmonics from random time series. The results highlight significant contributions of higher-order harmonics across various sea states. Specifically, two physical models were employed: a flexible monopile to capture structural hydroelastic deformations during large wave events and a rigid monopile to accurately estimate hydrodynamic loads without hydroelastic effects. Additionally, numerical results from fully nonlinear potential-flow calculations were compared, revealing that while the potential-flow solver underestimates total wave loading, especially for higher harmonics. In terms of the free-surface elevations and hydrodynamic forces, this study confirms that their higher-order harmonics align well with the scaling of their corresponding linear components in both amplitude and phase. This enables the prediction of higher-order profiles based solely on their linear components. However, this efficient model is inadequate for accurately estimating the higher-order harmonics of monopile's hydroelastic responses during these extreme wave events, highlighting the need for further refinement.

Accurate simulations of moving flexible objects with an improved immersed boundary-lattice Boltzmann method

Accurately capturing boundaries is crucial for simulating fluid–structure interaction (FSI) problems involving flexible objects undergoing large deformations. This paper presents a coupling of the immersed boundary-lattice Boltzmann method with a node-based partly smoothed point interpolation method (NPS-PIM) to enhance the accuracy of simulating moving flexible bodies in FSI problems. The proposed method integrates a multiple relaxation time scheme and employs a force correction technique to address boundary capturing inaccuracies. The effect of virtual fluid is accounted for through a Lagrangian point approximation, ensuring precise FSI force calculations for unsteady solid motions. NPS-PIM is utilized as the solid solver, constructing a moderately softened model stiffness by combining the finite element method (FEM) with the node-based smoothed PIM (NS-PIM). Simulations of flow fields near flexible objects with large deformations demonstrate that the proposed approach reduces numerical errors, improves computational efficiency compared to traditional FSI models using FEM and NS-PIM, and accurately captures the behavior of moving flexible bodies and detailed flow fields.

A 4D Soil-Structure Interaction Model Testing Apparatus

Abstract A new three-axis loading frame has been developed to enable real-time visualization of in-situ soil and rock structure interactions via X-ray tomography during small-scale model testing. The constructed frame is capable of performing a wide range of small-scale 1g tests and can accommodate monotonic and cyclic actuation under both load and displacement control. The compact size of the system enables remote multi-axis operation from within an X-ray cone-beam scanning bay, a capability which is owed to a comprehensive design process. Design and fabrication involved a blend of physical and numerical experiments to assess suitable construction materials and performance. In this scope, the new equipment is discussed and its capability is showcased.

Blood flow through a stenosed left anterior descending coronary artery: Evaluation of loss coefficients in one-dimensional fluid–structure interaction model

Coronary arterial flow is affected by conditions such as atherosclerosis and stenosis resulting in coronary artery disease. Quantifying the flow fields across arteries is a key aspect in the functional assessment of occlusive arterial disease. An essential aspect of blood flow modeling is the mechanical interaction between the fluid flow and the arterial vessel wall. The present study focuses on the modeling of blood flow within the left anterior descending artery affected with stenosis. A one-dimensional (1D) model was developed to study the transient blood flow characteristics in the artery. The 1D model is coupled with the material tube law to account for the flexibility of the arterial wall. The loss coefficients that account for the local viscous and turbulent losses across the stenosis region are estimated accurately in terms of the varying local cross-sectional area, instead of empirical constants used in the literature. It was observed that the magnitude of viscous losses decreases with an increase in the severity of stenosis. For lower degree of stenosis (<30%), the local turbulent losses are insignificant compared to the viscous losses. The maximum deformation of the vessel wall is ∼0.12mm at t=0.45s for s=70%. During the cardiac cycle (T=0.9s), the artery is observed to be experiencing dilation (Δr>0) in the upstream region, whereas contraction (Δr<0) in the downstream region for all the values of severity (s). A fractional flow reserve of 58.53% was noticed in a stenosed artery of 70% severity.

Numerical simulation progress of whole-heart modeling: A review

Cardiovascular diseases, characterized by high mortality rates, complex etiologies, and challenging prevention and treatment strategies, have become a major focus of public concern. With the advancement of computational numerical simulation technologies, whole-heart modeling has emerged as a crucial direction in cardiovascular engineering research. This review summarizes the progress in numerical simulations of whole-heart models, with a particular emphasis on the modeling and computation of cardiac-related physical fields. Through a retrospective study, this article covers various modeling approaches, including electrophysiological simulations, cardiac mechanics, and fluid–structure interaction models. Advanced theoretical models and numerical techniques are discussed in depth to enhance the accuracy and relevance of the simulations. Currently, numerical simulation techniques for whole-heart modeling have developed a relatively complete theoretical framework to compute key cardiac functions. However, there remains a need for further exploration in multiphysics coupling and high-performance computing to support clinical applications, requiring additional theories and methods. The integration of multiphysics and multiscale modeling is critical for advancing personalized medicine and improving the diagnosis and treatment of cardiovascular diseases. Future research will focus on enhancing computational efficiency and expanding clinical applications.

A coupled peridynamics–smoothed particle hydrodynamics model for fluid–structure interaction with large deformation

Fluid–structure interaction (FSI) is ubiquitous in various engineering disciplines, and effectively managing FSI often appears to be the key for successful failure analysis and safety-oriented design. Smoothed particle hydrodynamics (SPH) serves as a potent nonlocal meshfree method for fluid dynamics modeling, while peridynamics (PD) demonstrates exceptional capability in addressing structural dynamics involving large deformations and discontinuities. Thus, leveraging their respective strengths in a combined approach holds significant promise for tackling FSI challenges. In this work, we propose a new peridynamics–smoothed particle hydrodynamics (PD-SPH) coupling model for addressing FSI. A stable and efficient coupling algorithm for data transfer between PD and SPH is put forward. In this coupling strategy, a PD particle directly participates in solving the SPH governing equations when it is identified to be within the support domain of an SPH particle. This can be done since the SPH quantities including the density, velocity, and pressure of a PD particle are naturally attainable within the framework of non-ordinary state-based peridynamics theory. Concurrently, in solving PD governing equations, reaction forces from SPH particles act as external forces for PD particles, determined straightforwardly through Newton's third law. As such, the proposed PD-SPH coupling strategy is straightforward to implement and offers high computational efficiency. Validation examples demonstrate that the proposed PD-SPH coupling model is computationally robust and adept at capturing physical phenomena in diverse FSI scenarios involving breaking free surfaces of fluid and large structural deformations of solid. Moreover, the proposed PD-SPH coupling model is flexible introducing no constraint conditions for applications and can accommodate different particle resolutions for PD and SPH domains. These features enable a broad application range of the proposed PD-SPH coupling model including simulations of explosion-induced soil fragmentation, rock fracture, and concrete dam failure, which will be conducted by authors in the near future.

Spatiotemporal mode extraction for fluid–structure interaction using mode decomposition

A fluid–structure interaction (FSI) analysis model was developed based on the partitioned coupling approach. The study analyzed the fluid and structure behavior in a well-established validation case known as the Turek–Hron FSI benchmark test. This test involves strong, unsteady interaction between fluid flow and an elastic flap behind a rigid cylinder. Comparison of the elastic flap displacement frequencies and amplitudes from the present FSI model with reference data showed good agreement, validating the model. Dynamic mode decomposition (DMD) was employed to extract fundamental structures from the complex spatiotemporal data obtained from the FSI analysis. In addition, a mode–sensing technique based on a greedy algorithm was developed, and significant modes were extracted with elastic flap displacement as a feature. The crucial modes for the elastic flap displacement were the second bending modes at specific frequencies. However, these results differed significantly from the natural frequencies of the second bending modes obtained via eigenmode analysis. This discrepancy can be attributed to the close coupling between the fluid and structure, which alters elastic deformation behavior. The study demonstrates the potential for straightforward extraction of essential fluid–structure coupling using FSI-DMD.

Advanced piezoelectric fluid energy harvesters by monolithic fluid–structure–piezoelectric coupling: A full-scale finite element model

A full-scale finite element model is presented for monolithic fluid–structure interaction (FSI) simulations of thin-walled piezoelectric fluid energy harvesters (PFEHs). Unlike widely used beam/plate-based models, our model employs a solid finite element discretization to precisely represent the complex PFEH designs involving microstructured transducers and non-uniform cantilevers. These features, plus the local FSI effects, are often ignored by simplified models. We applied the Galerkin method to formulate the weak form of the mixed equation system, integrating the flow dynamics, the geometrically nonlinear cantilever, the piezoelectric components, the electrode, and the output circuit within a closed-circuit electro-mechanical coupled system. The coupling of the multiple domains is achieved through boundary-fitted discretization within a monolithic scheme, using shifted-Crank–Nicolson temporal integration. This work explored implementing piezoelectric FSI systems within the FEniCS-based TurtleFSI library, and experimented techniques such as employing penalty functions for achieving electrode components with uniform electric potentials. We investigated various advanced PFEH features, including the baseplate design, the arrangement and microstructure of the piezoelectric components, and their influence on the system's dynamic and energy output behavior. The results confirmed the model's key advantages: full-scale modeling allows the integration of complex base structures and transducer microstructures in PFEH design. Combined with monolithic FSI coupling, it offers greater versatility, supporting a wider range of fluid environments and configurations in both wind and hydropower harvesting. Additionally, the modeling strategy can be intended not only to enhance power output, but also to minimize material usage, reduce mechanical fatigue, and extend the operational lifespan of PFEH systems.

Mechanism of airfoil stall flutter: New insights from global linear stability analysis

Stall flutter is a self-excited aeroelastic vibration phenomenon that occurs in lifting systems near the stall angle of attack, characterized by the distinct single-degree-of-freedom behavior. Despite its significance, this phenomenon remains not fully understood and is often vaguely attributed to nonlinear effects. To address this gap, the present study aims to reveal the underlying fluid–structure interaction mechanisms of stall flutter through global linear stability analysis (LSA). For this purpose, a reduced-order model (ROM)-based aeroelastic stability analysis framework is established using the autoregressive with exogenous input method. The ROM-based aeroelastic model provides a low-order representation of the coupled dynamics near the equilibrium steady state and can accurately capture the stability characteristics of the fluid-elastic system. It is found that as the angle of attack approaches the static stall angle, a low-frequency weakly stable fluid mode emerges, whose frequency is sufficiently lower than that of the von Kármán vortex shedding. The interaction between this fluid mode and the structure mode ultimately leads to the instability of the aeroelastic system at high reduced velocities, which is the fundamental cause of stall flutter. Moreover, dynamic mode decomposition is employed to successfully extract the spatial coherent structures and frequency characteristics of this low-frequency fluid mode, thereby confirming the validity of the LSA results. Further analysis indicates that, as the angle of attack decreases, this low-frequency fluid mode gradually weakens and eventually degenerates into more stable non-oscillatory fluid modes, resulting in structural stabilization and the cessation of stall flutter. Overall, the linear dynamic model accurately predicts the onset of instability and the vibration frequency of the airfoil, which challenges the traditional nonlinear perspectives and supports the feasibility of using linear control theory for stall flutter suppression in future research.

Dynamics of fluid–structure interaction in paintbrush

Fluid–structure interactions are fundamental in both natural phenomena and industrial applications, particularly in dip-coating processes where withdrawal velocity and drainage dynamics are crucial. Understanding these interactions is essential for optimizing various processes, from enhancing the efficiency of industrial coatings to developing advanced materials with tailored properties. Here, we examine the capillary-induced dynamics of fiber bundles using paintbrush-like structures. We submerge fiber bundles in water and withdraw them at various velocities, observing that water trapped within the bundles leads to capillary-driven fiber assembly. Our experiments show that the bundle diameter after emergence increases with higher withdrawal speed due to viscous effects. We develop a theoretical model that accurately predicts the dynamics of fiber assembly driven by capillary and viscous flows. The mathematical model agrees well with our experimental results, demonstrating the complex interplay between capillary forces and fiber packing. We anticipate that our findings improve the understanding of fluid-structure interactions in fibrous media, providing physical insights that can be applied to more complex systems such as nanopattern collapse and nano/micro-manufacturing.

Fluid–structure interaction analysis of a helico-axial multiphase pump under fluctuating incoming flow conditions

Fluid–structure interaction analysis of a helico-axial multiphase pump under fluctuating incoming flow conditions

Numerical study of liquid sloshing in three-dimensional flexible cylindrical tank under multi-directional seismic excitation

The present study aims to evaluate the effect of the flexibility of three-dimensional (3D) cylindrical tank on liquid sloshing inside the tank as well as the influence of the hydrodynamic forces on the structure's deformation. A ground-supported cylindrical flexible tank filled with water and subjected to seismic excitation is investigated using a numerical coupling methodology to take into account the fluid–structure interactions. The Navier–Stokes equations in the fluid domain are solved using the finite volume method, while the finite element method is used to solve the linear-elastic equations of the structure. The arbitrary Lagrangian–Eulerian formulation is applied for the moving mesh in two-phase flow system. The simulations are conducted using free open-source software: OpenFOAM for fluid dynamics and FEniCS for solid mechanics, both utilize the preCICE library for data exchanging and fluid–structure coupling. The numerical methodology is validated by the experimental and numerical results given in literature. A multi-directional earthquake ground motion is then considered as external loading, and the elasticity of the tank wall is varied to investigate the effect on the fluid sloshing. It has been shown that the more flexible the tank walls are, the greater will be both the sloshing height and the structural deformations during an earthquake event. Several flow field information and structural responses have been provided, such as the sloshing height, hydrodynamic pressure, structure deformations, and structural stress distribution. The potential elephant's foot buckling phenomenon at the lower part of tank can also be predicted.

Dynamic modeling of air–metal plasma mixture of single-turn coil with erosion at megaGauss magnetic field

Single-turn coil (STC) is a destructive pulsed magnet aiming at 100–300 T magnetic field. Due to the high discharge current, the conductor of STC is heated rapidly and undergoes melting and vaporization, leading to the generation of supersonic air–metal vapor mixed plasma jet and the magneto-fluid effect. In this study, the mixed plasma mass-transfer and fluid dynamic characteristics are modeled at megaGauss magnetic field, high temperature, high pressure, and supersonic conductor shock deformation. The collision integral method is employed to calculate the fluid transport properties. In addition, a boundary constraint model of fluid–structure interaction (FSI) compatible with both fluid wall boundary condition and plasma jet entrance condition and a model to simultaneously solve the thermal ionization and high electric field ionization of the mixed vapor are proposed. As the result, the distributions of plasma electrical conductivity, current density, electron, heavy particles, temperature, air body load, and velocity are derived. Especially, the region of highest electrical conductivity is not the air domain near the inner surface of the conductor with the highest electron density and the highest magnetic field, but the air domain near the outer surface of the conductor with the relatively higher electron density and lower magnetic field.

Physical properties of Korean normal aortic valves based on fluid–structure interactions

Recently, numerical methods such as computational fluid dynamics (CFD), have been widely used in heart valve research. The CFD approach has fewer restrictions compared to clinical and experimental methods as it involves interpretations through computer calculations, and it can be used to predict and analyze fluids. For valve numerical analysis using CFD, the mechanical properties of the valve must be defined based on the physical properties. However, most of the existing heart valve numerical analysis studies have been conducted for westerners, and only a few studies on the same topic have focused on Asians. Thus, in this paper, we aim to determine the physical property parameters suitable for defining the mechanical properties of the normal aortic valves of Koreans over time. In this study, we used a fluid−structure interaction technique for the valve simulation and applied three representative valve characteristics presented in previous aortic valve simulation studies. Herein, the valve patency rates in case of simulation and multidetector computed tomography images were compared and analyzed through statistical techniques. Our results revealed that the physical properties, such as density (1050 kg/m3), Young’s modulus (2 MPa), and Poisson’s ratio (0.3), are like those of the Korean aortic valve over time. If hemodynamic evaluation of the Korean aortic valve is performed through simulation using these conditions, it can be effective in identifying the factors of heart valve disease.

Multifunctional Nacre-Like Nanocomposite Papers for Electromagnetic Interference Shielding via Heterocyclic Aramid/MXene Template-Assisted In-Situ Polypyrrole Assembly

HighlightsThe large-scale, high-strength, super-tough, and multifunctional nacre-like heterocyclic aramid (HA)/MXene@polypyrrole (PPy) (HMP) nanocomposite papers were fabricated using the in-situ assembly of PPy onto the HA/MXene hydrogel template.The "brick-and-mortar" layered structure and abundant hydrogen-bonding interactions among MXene, PPy, and HA respond cooperatively to external stress and effectively increase the mechanical properties of HMP nanocomposite papers.The templating effect from HA/MXene was utilized to guide the assembly of conducting polymers, leading to high electrical conductivity and outstanding electromagnetic interference shielding performance.

Comparative Analysis of Soil-Piles Structure Interaction of Framed Structure

This study presents a comparative analysis of a 15-story building with two foundational approaches: a fixed- base foundation and a pile foundation incorporating soil- structure interaction (SSI) in sandy soil conditions. The research investigates the dynamic behavior of each foundation type under varying conditions, specifically examining the effects of different pile spacings and relative densities of sandy soil on the building’s fundamental frequency, time period, lateral displacement, and overall structural stability. The SAP2000 software is used for numerical study. Key Words: Soil-Structure Interaction (SSI), frequency, time period, displacement, Lateral Displacement, Seismic Analysis, G+14, SAP2000, sandy soil

Genome-Wide Identification, Characterization and Expression Patterns of the DBB Transcription Factor Family Genes in Wheat.

Double B-box (DBB) proteins are plant-specific transcription factors (TFs) that play crucial roles in plant growth and stress responses. This study investigated the classification, structure, conserved motifs, chromosomal locations, cis-elements, duplication events, expression levels, and protein interaction network of the DBB TF family genes in common wheat (Triticum aestivum L.). In all, twenty-seven wheat DBB genes (TaDBBs) with two conserved B-box domains were identified and classified into six subgroups based on sequence features. A collinearity analysis of the DBB family genes among wheat, Arabidopsis, and rice revealed some duplicated gene pairs and highly conserved genes in wheat. An expression pattern analysis indicated that wheat TaDBBs were involved in plant growth, responses to drought stress, light/dark, and abscisic acid treatment. A large number of cis-acting regulatory elements related to light response are enriched in the predicted promoter regions of 27 TaDBBs. Furthermore, some of TaDBBs can interact with COP1 or HY5 based on the STRING database prediction and yeast two-hybrid (Y2H) assay, indicating the potential key roles of TaDBBs in the light signaling pathway. Conclusively, our study revealed the potential functions and regulatory mechanisms of TaDBBs in plant growth and development under drought stress, light, and abscisic acid.