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Water entry of deformable bodies has been investigated extensively despite the major challenges in precise simulations of the whole physical process. Inspired by the basic idea of immersed boundary method (IBM), a hybrid FEM-IBM-level set algorithm is proposed where structural compliance is considered. The flow is described by Navier-Stokes equations with an added body force while the drastically moving object of arbitrary geometry is represented by several Lagrangian points on solid boundary. The direct forcing IBM is enhanced and coupled with finite element method (FEM) to facilitate simulation of severe fluid-structure interactions. Consequently, the added body force is calculated implicitly based on the exact velocity boundary condition with divergence-free condition ensured simultaneously. The improved conservative level set technique is adopted for accurate depiction of instantaneously distorted water surface, and the strongly coupled system is resolved iteratively through a partitioned scheme. Examples including sedimentation of a disk, water entry of deformable wedge and cylindrical shell are performed for validation. Specifically, hydroelastic impact of a three-dimensional conical shell is investigated, and the influence factors of entry dynamics are discussed. The results demonstrate the reliability and great potential of present algorithm for practical applications in ocean engineering, naval architecture and military engineering, etc. • Innovative algorithm for water entry of flexible body is presented. • Strong coupling effect among heterogeneous phases is achieved. • Mechanical behaviors of arbitrary shaped body could be reasonably reflected. • The influence factors of 3D water entry behaviors are revealed. • The versatile method enables precise simulations of practical hydroelastic problem. [ABSTRACT FROM AUTHOR]

• A multiphase reactive transport pore-scale model is improved. • Negative feedback between multiphase flow and solid dissolution is revealed. • Multiphase flow can promote the compact solid dissolution in porous media. • Structure heterogeneity effect is not intensified in the multiphase dissolution. • A new correlation between porosity, saturation and interfacial length is proposed. Fundamental understanding of the multiphase reactive transport with solid dissolution is crucial for a wide range of scientific and engineering problems. In this study, a pore-scale model is improved to study coupled processes of multiphase flow, mass transport, chemical reaction and solid dissolution in porous media with increasing structural heterogeneity. The results show that with the existence of multiphase flow, under the reactive transport conditions studied (Pe = 5, Da = 10; and Pe = 5, Da = 1), more compact dissolution pattern is generated due to the negative feedback between reactant transport and solid dissolution, while the feedback is positive in single-phase condition leading to wormhole dissolution. Besides, while it is found that the structural heterogeneity amplifies the wormhole dissolution in single-phase reactive transport processes or promotes the formation of fingering for multiphase flow, such heterogeneity effect is homogenized in the multiphase case. Finally, based on the pore-scale results, a new correlation between porosity, saturation and interfacial length is proposed which can be upscaled into the continuum-scale models. [ABSTRACT FROM AUTHOR]

The numerical investigation of vortex-induced vibration (VIV) of a porous-coated cylinder in a two-dimensional incompressible turbulent flow is studied at subcritical Reynolds number by using finite volume method based software OpenFOAM. The mass ratio and damping ratio of the system are fixed at m∗ = 2.4 and ζ = 5.42 × 10−3, respectively. To account for the influence of the porous medium on the turbulent variables, a combined k - ε model is proposed, which combines the advantages of both the Renormalization Group (RNG) k - ε model and the Launder-Sharma (LS) k - ε model. The effect of the Darcy number (Da = 10−4, 10−3, and 10−2), the relative layer thickness (h∗ = 0.1 and 0.2), and reduced velocity (2≤ U r ≤ 11) on the vortex shedding pattern, vibration amplitude, and dynamic forces on the system are investigated. Results show that the porous coatings with larger thicknesses and Da = 10−3∼10−2 effectively suppress VIV, in which case the vibration amplitude is decreased by up to 95.5%. The total drag on the cylinder is increased for Da≤10−3. • A combined k - ε model simulates VIV of a porous-coated cylinder in the turbulent regime. • VIV response is significantly suppressed by the porous coating with Da = 10−3∼10−2. • The total drag on the coated cylinder is higher for Da≤10−3 from Re > 5000. • A thicker porous layer achieves better performance in controlling VIV. [ABSTRACT FROM AUTHOR]

In this paper, the lattice Boltzmann method (LBM) and the discrete element method (DEM) are coupled to simulate the interaction between the fluid phase and irregularly shaped solid particles. For this purpose, the geometry of realistic particle shapes is represented as clumps of overlapping spheres and then simulated through a multi-sphere model in DEM and coupled with LBM using two open-access codes, LIGGGHTS and Palabos. The accuracy of the coupling method with clumps is demonstrated by simulating several benchmark cases and comparing them with the results from the literature. The coupled LBM-DEM method is then used to simulate the collapse and transport of submerged granular particles with spherical shape and irregular shape, respectively, to highlight the influence of grain morphology in the solid–fluid interaction. Compared with previous LBM-DEM coupling for highly idealized non-spherical shapes, the research provides a more realistic computational framework to capture the complex irregular particle shapes of geomaterials with clumps/multi-spheres, which is useful for studying the underlying effect of particle shape on geotechnical issues such as internal erosions. [ABSTRACT FROM AUTHOR]

The study of fluid–structure interactions in elastic structures is highly important in hydraulic structural engineering. This paper adopts the smooth particle hydrodynamics (SPH) coupling method to simulate dam failure water impact elastic plate flow and solid coupling problems. In addition, a numerical simulation is performed on the study of the free surface flow impact of the elastic plate structure on the main dynamic characteristics, including the impact force distribution and the change process. Additionally, the elastic structure of the vibration amplitude and frequency change rule, as well as the drastic changes in free surface flow, are also carried out. In this paper, the synchronous finite element algorithm is used to analyze the problem to obtain FEM results Additionally, two-dimensional benchmark physical tests are designed for dam-break water flow impacting an elastic plate are conducted, focusing on a comparative analysis of the numerical results of the SPH method with the results of physical tests and verifying the validity, accuracy, and superiority of the SPH coupling method for solving the problem of fluid‒solid coupling in elastic structures. On this basis, to explore the relevant physical quantities that cannot be measured or described during the test process, the flow–solid coupling characteristics of the elastic plate impacted by water flow are further understood by analyzing the nature of the flow field, the change in the flow–solid force of the elastic plate and the change rule of the frequency spectrum. The results show the following: (i) The jumps in velocity between the streams and the strong curvature of the free liquid surface lead to the creation of vortices at the cavities. (ii) The flow solid force under the impact of water flow increases and then decreases, and the smaller the deformation of the elastic structure is, the greater the force is. (iii) The vibration frequency of the fixed end of the elastic structure gradually decreases along the free end frequency, and the larger the deformation of the free end of the elastic plate is, the weaker its vibration response is. In addition, the natural frequency of the elastic plate under water flow impact is slightly lower than that under free vibration of the elastic plate. The related research results provide reference and guidance for the fluid–structure interaction problem. • Physical tests of elastic plates impacted by dam break water flow are studied. • Dynamic characteristics of elastic structures based on the SPH solver are analyzed. • The generation of vorticity, fluid-solid forces, and spectral changes are analyzed. • The water flow impacting the elastic plate based on SPH and FEM solver is studied. [ABSTRACT FROM AUTHOR]

The mechanical and thermo-physical properties of a coating material affect the lubrication performance. The present study aims at to investigate the effect of mechanical and thermo-physical properties of coating material on the lubrication performance of rolling contact operating under Thermal Elasto-Hydrodynamic Lubrication (TEHL) regime. The mechanical and thermo-physical properties of the coating material considered in the present analysis are elastic modulus, density, thermal conductivity and specific heat. Furthermore, the effect of coating thickness is also studied. The Commercial Multiphysics software ANSYS is used in the present analysis to model and analysis of the finite line contact obtained in the rolling contact. It is observed that the pressure intensity increases with the elasticity of the coating. The maximum fluid pressure developed at the contact region 1.2GPa with the application of material possessing higher modulus of elasticity i.e. 420 GPa. With increase in coating thickness the contacts width reduces. The material having lower density, thermal conductivity and heat capacity exhibits as an insulating material which obstructs the transfer of heat from the fluid to the contacting surfaces. This leads to increase the temperature of the lubricant. With these properties the maximum developed temperature observed to be 351K. [ABSTRACT FROM AUTHOR]

Target signatures are discrete quantities computed from measured scattering data that could potentially be used to classify scatterers or give information about possible defects in the scatterer compared to an ideal object. Here, we study a class of modified interior transmission eigenvalues that are intended to provide target signatures for an inverse fluid–solid interaction problem. The modification is based on an auxiliary problem parametrized by an artificial diffusivity constant. This constant may be chosen strictly positive, or strictly negative. For both choices, we characterize the modified interior transmission eigenvalues by means of a suitable operator so that we can determine their location in the complex plane. Moreover, for the negative sign choice, we also show the existence and discreteness of these eigenvalues. Finally, no matter the choice of the sign, we analyze the approximation of the eigenvalues from far field measurements of the scattered fluid pressure and provide numerical results which show that, even with noisy data, some of the eigenvalues can be determined from far field data. [ABSTRACT FROM AUTHOR]

pH-sensitive hydrogels are classified as soft materials that can be employed for future imaginative applications due to their interesting characteristics. Smart hydrogels undergo large deformation under exterior stimuli. However, the swelling behaviors of hydrogels that can be harnessed for microfluidic applications are not well perceived. In this paper, the functionality of an assortment of micro-valves which are composed of pH-sensitive cylindrical hydrogel jackets coated on rigid pillars is inspected considering fully coupled fluid–solid interaction analysis. Therefore, in order to introduce the theory of transient swelling of a pH-sensitive micro-check valve, a transient constitutive model capturing electrical, chemical, and mechanical fields for the hydrogel domain is utilized with fluid fields passing around the micro-valve. In this regard, the Nernst–Planck equation is employed to describe the ions' diffusion, and Gent hyperelastic model is used to account for the large deformation of the hydrogel. Implementing this nonlinear finite element framework, we examine the performance of one cylindrical jacket and also three patterns of multiple cylindrical valves considering transient 3D FSI behavior of the hydrogel micro-valve. The foremost emphasized novelty of this paper is considering three-dimensional geometry, new designs of micro-valves, and time-dependent swelling of hydrogels by coupling ions diffusion and their large deformation. Article Highlights: Three-dimensional single and multiple pH-sensitive hydrogel micro-valves Electro-chemo-mechanical theory for pH-sensitive hydrogels to predict their transient swelling Fluid–solid interaction of Newtonian fluid and hydrogel which can undergo large reversible deformation [ABSTRACT FROM AUTHOR]

The aim of the present paper is the study of interaction of the abrupt wave with vertical and inclined rectangular obstacles. For this purpose, in the first step, two experiments have been done. The tests were performed with smooth rectangular cross-section channels, and related data were extracted using digital image processing. Flow behavior was recorded with one adjacent CCD camera through the glass walls of the entire downstream channel. In the second step, the numerical study has been done by a mesh-free particle Lagrangian method (Incompressible Smoothed Particle Hydrodynamics, ISPH) and a mesh-based Eulerian method (Finite Volume Method with Volume of Fluid surface tracking approach, FV-VOF). The capabilities of the numerical methods in simulation of the sudden variations free surface flows have been assessed. A comparison between the computed results and the experimental data shows that both numerical models simulate the mentioned flows with reasonable accuracy.

In this study, the active vibration control of a rectangular plate submerged in water was investigated. Mass dampers were attached to the plate, and the system was modeled via assumed mode. Water is modeled as an inviscid fluid with moving boundaries at fluid–solid interaction surfaces and applied forces on the plate being calculated by Bernoulli equation. The natural frequencies of the plate in vacuum and in water (for partial and fully submerged cases) found from numerical calculations are compared with experimental results to prove the accuracy of the model. Subsequently, for frequency computations, particular frequencies were chosen and active damping was applied for them. To actively control the plate’s vibration by a moving mass with static stable methods, the displacement data of some points were used as input. First, to increase the damping of target mode at low-frequency, the negative acceleration feedback control algorithm in modal-space was applied. Then, the decentralized method was examined. Both methods were successful in suppressing vibration of the submerged rectangular plate.

pH-sensitive hydrogels are promising materials to be employed in microfluidic devices, especially microvalves. In this paper, a theory of transient swelling of pH-sensitive micro-valve is presented. A transient constitutive model that captures electrical, chemical, and mechanical fields is considered to model the swelling phenomenon. The diffusion of ions into the hydrogel, the electromigration, and convection are described by implementing the Nernst-Planck equation. Assuming Gent model, hydrogel is considered as a compressible hyperelastic material and osmotic pressure is assumed as an external loading. Due to benefits of in-plane valves, a design of the micro-valve is studied. Design simplicity and great sealing are vital factors which can be considered as an advantage of this valve for fabrication. This design and modeling approach has not been used for pH-sensitive hydrogels in earlier works. Thus, we have studied the transient swelling of pH-sensitive hydrogel microvalve, when effects of fluid-structure-interaction are examined on valve performance. It is noted that in most previous studies, equilibrium conditions have been assumed. While considering transient fully-coupled fluid-structure-interaction is necessary to capture a more realistic modeling. The results illustrate that the microvalve blocks the channel much earlier than reaching the equilibrium-state, which implies importance of the transient behavior of hydrogels. [ABSTRACT FROM AUTHOR]

Target signatures are discrete quantities computed from measured scattering data that could potentially be used to classify scatterers or give information about possible defects in the scatterer compared to an ideal object. Here, we study a class of modified interior transmission eigenvalues that are intended to provide target signatures for an inverse fluid–solid interaction problem. The modification is based on an auxiliary problem parametrized by an artificial diffusivity constant. This constant may be chosen strictly positive, or strictly negative. For both choices, we characterize the modified interior transmission eigenvalues by means of a suitable operator so that we can determine their location in the complex plane. Moreover, for the negative sign choice, we also show the existence and discreteness of these eigenvalues. Finally, no matter the choice of the sign, we analyze the approximation of the eigenvalues from far field measurements of the scattered fluid pressure and provide numerical results which show that, even with noisy data, some of the eigenvalues can be determined from far field data. [ABSTRACT FROM AUTHOR]

In this paper, the elasto-hydrodynamic (EHD) performance of partial journal bearings has been studied. A numerical analysis has been conducted using the ANSYS Workbench (17.2) platform to investigate the performance of partial journal bearings. The lubricant used is considered Newtonian and incompressible fluid that flows steadily under laminar conditions, while the bearing material is assumed to be elastic, isotropic with smooth surface conditions. In the current FSI analysis, the lubricant flow has been predicted according to the finite_ volume method, while the finite element method has been adopted to compute the deformation and stress in the bearing surface.

Abstract This paper is concerned with the inverse scattering of time-harmonic acoustic plane waves by a multi-layered fluid–solid medium in the three dimensional space. We establish the global uniqueness in identifying the embedded penetrable solid obstacle, the surrounding fluid medium and its wave number from the acoustic far-field pattern for all incident plane waves at a fixed frequency. The proof depends on constructing different kinds of interior transmission problems in appropriate small domains and the a priori estimates derived for both the elastic wave fields in the embedded solid obstacle and the acoustic wave fields in the surrounding fluid medium.

Tornados are one of the most common natural disasters, but their occurrence can be sudden and unpredictable. For trains operating in the areas where tornadoes frequently happen, the operation safety is challenged. Tornado generator was recently proposed as a method of numerical investigation of tornado-like vortex flows. This paper presents a numerical approach for the simulation of train passing through a tornado-like vortex on realistic scale. It is found that the tornado-like vortex causes appearance of localized regions of a negative pressure on the train and transient variations of the aerodynamic loads acting on the train. As a result, the tornado-like vortex causes swings on the lateral force, and subsequently on the rolling moment, which affect the passenger comfort and operation safety of the train. The method presented herein can be further applied to the study of train behavior and real time response while encountering tornadoes of different types and strength, which is significant for evaluating the operation safety of high-speed trains.

Aerodynamic forces due to blade-tip clearance eccentricity are a known destabilizing source in rotating machinery with unshrouded impellers. Dynamic forces also appear in shrouded impellers, due to changes in the pressure in the gap between the impeller casing and its shroud. These are load-dependent forces typically characterized by a cross-coupled stiffness coefficient (k > 0). This paper reviews the archival literature for quantification of blade-tip clearance induced forces and impeller-casing forces in both unshrouded and shrouded turbines and compressors. Most distinctive are the lack of experimental results and the indiscriminate application of simple formulas to predict k, including Alford’s and Wachel’s equations. The disparity in estimations of the destabilizing k extends to recent CFD models and results. Hence, rotordynamic predictions vary widely. This review reveals that engineering practice ignores accurate physical models that could bridge the gap between practice and theory. As the energy market shifts toward carbon capture and hydrogen compression, accurate knowledge of aerodynamic forces from unshrouded compressors and open impellers will become necessary in multi-stage rotors.

It is of great significance to study the seepage characteristics of heavy oil reservoirs, which are conducive to the efficient development of resources. Boundary layer effect (BLE) exists in the pore-scale flow process of macromolecular fluid media, which is different from the flow law of conventional fluid in the pore, yet the influence of BLE is ignored in the previous pore-scale simulation. Conventional porous media simulations have difficulty analyzing the mass transfer law of small-scale models under the influence of microfractures. Based on the CT scanning data and thin section data of the real core in the target area, the rock skeleton and flow space were extracted according to the maximum ball algorithm, and the pore network model representing the complex structure was constructed. The microscale effect of macromolecules in the flow process in the pores was characterized by modifying the effective flow. The effects of the BLE on the effective connectivity, displacement process, and oil distribution law were analyzed. The seepage characteristics of different wettability conditions and different water cut stages were compared. The results show that BLE reduces the effective flow space and leads to deviations in the relative permeability curve and capillary curve. For fractured porous media, the irregular shape of porous media was characterized by the morphological method, and the mass transfer process was analyzed by the equivalent flux method. The influence of the porous media shape on the macromass transfer process was compared. This study provides a solution to the problem of BLE in pore-scale simulation.

The aim of this study is to analyse the behaviour of a thin plate with air flow velocities of 0.3–0.9 Ma. Data from the experiment and numerical tools were used for the analysis. For fluid–solid interaction calculations, the arbitrary Lagrange–Euler approach was used. The results of the measurements are twofold. The first one is the measurement of the flow before and after vibrating plate, i.e. pure flow plate, and the second consists in measuring the characteristics of vibration of the plate. The character of the vibration was measured with an oscilloscope, and then the results were subjected to FFT analysis to determine the natural and flow induced vibrations. For numerical calculations example, the velocity of 0.7 Ma was selected. The deflections of the platelet under the influence of airflow were obtained. The trace of the friction layer that forms the boundary between the flow from the platelet and the separation formed behind the platelet. [ABSTRACT FROM AUTHOR]

This paper is devoted to studying impedance eigenvalues (that is, eigenvalues of a particular Dirichlet-to-Neumann map) for the time harmonic linear elastic wave problem and their potential use as target signatures for fluid-solid interaction problems. We first consider several possible families of eigenvalues of the elasticity problem, focusing on certain impedance eigenvalues that are an analogue of Steklov eigenvalues. We show that one of these families arises naturally in inverse scattering. We also analyze their approximation from far field measurements of the scattered pressure field in the fluid and illustrate several alternative methods of approximation in the case of an isotropic elastic disk. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering Geology / Gongcheng Dizhi Xuebao is the property of Journal of Engineering Geology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Summary: We present an adaptive isogeometric‐analysis approach to elasto‐capillary fluid‐solid interaction (FSI), based on a diffuse‐interface model for the binary fluid and an Arbitrary‐Lagrangian‐Eulerian formulation for the FSI problem. We consider approximations constructed from adaptive high‐regularity truncated hierarchical splines, as employed in the isogeometric analysis (IGA) paradigm. The considered adaptive strategy comprises a two‐level hierarchical a posteriori error estimate. The hierarchical a posteriori error estimate directs a support‐based refinement procedure. To attain robustness of the solution procedure for the aggregated binary‐fluid‐solid‐interaction problem, we apply a fully monolithic solution procedure and we introduce a continuation process in which the diffuse interface of the binary fluid is artificially enlarged on the coarsest levels of the adaptive‐refinement procedure. To assess the capability of the presented adaptive IGA method for elasto‐capillary FSI, we conduct numerical computations for a configuration pertaining to a sessile droplet on a soft solid substrate. [ABSTRACT FROM AUTHOR]

In this study, the flagellar motility of a swimmer microorganism as a model of a human sperm cell, inside a two-dimensional channel as a model of the female reproductive tract containing a viscous fluid, is numerically investigated. The Navier–Stokes equations governing the fluid are coupled with the equations governing the models flagellum via applying a fluid–solid interaction approach and then solved using the finite element method. To stimulate the flagellum to move, a prescribed sinusoidal waveform is applied to it. The strain induced by this waveform along the flagellum initiates a continuous interaction between the flagellum and the fluid. The simulations are validated using data available in the literature. A very good agreement is seen between them. The results show that by decreasing the Young modulus of the flagellum as well as increasing the fluid viscosity, the swimming velocity of the model significantly decreases. It is found that for lower Young modulus of the flagellum, the effect of the fluid viscosity on the flagellar deformation is stronger. It is also found that for higher amplitude of the waveform applied to stimulate the flagellum, both the swimming velocity of the model and the average work rate are greater. Moreover, it is found that in a channel with a smaller height, the model swims at a higher speed and with a higher average work rate. [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A multibody dynamics-based solution to the fluid dynamics problem is compared herein to two established Lagrangian-based techniques used by the computational fluid dynamics (CFD) community. The multibody dynamics-based solution has two salient attributes: it enforces the incompressibility condition through bilateral kinematic constraints, and it treats the coupling with the solid phase via unilateral kinematic constraints. The multibody dynamics-based solution, called herein the Kinematically Constrained Smoothed Particle Hydrodynamics (KCSPH) method, is a Lagrangian approach to solving the CFD problem. It relies on the Smoothed Particle Hydrodynamics (SPH) method to discretize the spatial differential operators in the Navier–Stokes equations, and on the Newton–Euler equations of multibody dynamics to convect the SPH particles forward in time. We show that the multibody dynamics-based approach is efficient and accurate by comparing its performance with the two most commonly used SPH algorithms in the CFD community: the weakly compressible SPH (WCSPH), and the implicit SPH (ISPH) methods. The comparison is carried out in conjunction with four tests: an incompressibility benchmark test, dam break, floating cylinder, and sloshing tank. We conclude that KCSPH is a robust alternative to conventional CFD approaches for fluid–solid interaction (FSI) problems with complex/moving boundaries. The solvers and models used herein are publicly available in an open-source software called Chrono; the implementations use GPU (for WCSPH and ISPH), and multicore CPU (for KCSPH) parallel computing. [ABSTRACT FROM AUTHOR]

To investigate the effect of the target weight coefficient on the structure design of the micro-channel heat sink, an innovative method for the topology optimization design of micro-channel structures with different bifurcation angles is adopted. In this study, the improved interpolation function, density filtering, and hyperbolic tangent projection methods are adopted to obtain a clear topological structure of the micro-channel heat sink. The heat transfer of the micro-channel heat sink under different bifurcation angles is compared. At the same time, the influence of the two different objective functions, heat transfer, and flow energy consumption, is analyzed in the topology optimization of micro-channel heat sinks. The results show that when the bifurcation angle is 135°, both the heat transfer and the average outlet temperature of the micro-channel heat sink obtain the maximum value, and the heat transfer effect is the best. With the increase of the heat transfer weighting coefficient, the distribution of solid heat sources in the main channel increases, and the refinement of the branch channels also increases. On the other hand, although the heat transfer effect of the micro-channel heat sink is the best, the corresponding flow energy consumption is larger.

A new method is proposed to solve the hydrodynamics performances of a fluid lubricated screw-nut pair using FLUENT. Before the simulations, the Computational Fluid Dynamics (CFD) model of the gap flow field is built, based on some approximation rules. During the simulations, the dynamic mesh technology is employed to realize the real-time update of the grids of the computational domain. For a given velocity perturbation, the stiffness and damping coefficients of the system are solved using the finite difference method, and the influences of the perturbations on the system are compared among different ranges. With the fluid–solid interaction and the real-time restriction of the restrictors considered, the system is solved under different loading conditions. A more accurate solution method for the dynamic stiffness and damping coefficients is provided, and the dynamics characteristics of the system after loading are analyzed. On this basis, a qualitative and quantitative comparison is carried out between the method based on the simplified Reynolds equation and the proposed method in this paper, showing the latter superiorities in illustrating the field. A general understanding of the dynamics properties under different loading conditions of the system is obtained through this research, providing a basis for the precision control of the system in the future research.

In the tea industry, achieving a high winnowing accuracy to produce high-quality tea is a complex challenge. The complex shape of the tea leaves and the uncertainty of the flow field lead to the difficulty in determining the wind selection parameters. The purpose of this paper was to determine the accurate wind selection parameters of tea through simulation and improve the precision of tea wind selection. This study used three-dimensional modeling to establish a high-precision simulation of dry tea sorting. The simulation environment of the tea material, flow field, and wind field wall were defined using a fluid–solid interaction method. The validity of the simulation was verified via experiments. The actual test found that the velocity and trajectory of tea particles in the actual and simulated environments were consistent. The numerical simulations identified wind speed, wind speed distribution, and wind direction as the main factors affecting the winnowing efficacy. The weight-to-area ratio was used to define the characteristics of different types of tea materials. The indices of discrete degree, drift limiting velocity, stratification height, and drag force were employed to evaluate the winnowing results. The separation of tea leaves and stems is best in the range of the wind angle of 5–25 degrees under the same wind speed. Orthogonal and single-factor experiments were conducted to analyze the influence of wind speed, wind speed distribution, and wind direction on wind sorting. The results of these experiments identified the optimal wind-sorting parameters: a wind speed of 12 m s−1, wind speed distribution of 45%, and wind direction angle of 10°. The larger the difference between the weight-to-area ratios of the tea leaves and stems, the more optimized the wind sorting. The proposed model provides a theoretical basis for the design of wind-based tea-sorting structures.

Elastic wave metamaterials have been widely exploited with their dynamic superior properties and outstanding acoustic responses. However, it is difficult to directly manipulate sound pressure in low frequencies. In this study, we propose a new kind of elastic wave metamaterial which consists of vertical and lateral resonators as well as orthogonal stiffeners. The active feedback control system is applied to extend to the tunable scope for both lower and higher frequency regions and change the characteristics of acoustic-structure coupling. Its effective mass density is also discussed with different feedback constants. In order to present effects of the fluid-solid interaction, we considered that the elastic wave metamaterial is immersed in different fluid medium and its sound transmission loss (STL) is calculated. This work provides a feasible method for creating mechanical/acoustic models with multi-functional potentials. [ABSTRACT FROM AUTHOR]

Bicuspid aortic valve (BAV) patients are conventionally not treated by transcathether aortic valve implantation (TAVI) because of anatomic constraint with unfavorable outcome. Patient-specific numerical simulation of TAVI in BAV may predict important clinical insights to assess the conformability of the transcathether heart valves (THV) implanted on the aortic root of members of this challenging patient population. We aimed to develop a computational approach and virtually simulate TAVI in a group of n.6 stenotic BAV patients using the self-expanding Evolut Pro THV. Specifically, the structural mechanics were evaluated by a finite-element model to estimate the deformed THV configuration in the oval bicuspid anatomy. Then, a fluid-solid interaction analysis based on the smoothed-particle hydrodynamics (SPH) technique was adopted to quantify the blood-flow patterns as well as the regions at high risk of paravalvular leakage (PVL). Simulations demonstrated a slight asymmetric and elliptical expansion of the THV stent frame in the BAV anatomy. The contact pressure between the luminal aortic root surface and the THV stent frame was determined to quantify the device anchoring force at the level of the aortic annulus and mid-ascending aorta. At late diastole, PVL was found in the gap between the aortic wall and THV stent frame. Though the modeling framework was not validated by clinical data, this study could be considered a further step towards the use of numerical simulations for the assessment of TAVI in BAV, aiming at understanding patients not suitable for device implantation on an anatomic basis. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin University of Science & Technology is the property of Journal of Harbin University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study numerically investigates the aerodynamic and aeroelastic characteristics of a square prism (aeroelastic model) and wind field around it in sinusoidal oscillatory flows (SOFs). The reliability of the fluid-solid interaction (FSI) simulation is validated by a free vibration test and wind tunnel tests in smooth flow and SOF. The effects of the amplitude and frequency of SOFs are studied at the mean wind speed of vortex-induced resonance. The results show that increasing the amplitude and frequency of SOFs will amplify the root mean square (RMS) along-wind and across-wind base shear forces of the aeroelastic model but decrease the RMS across-wind displacement at the top of the aeroelastic model. The spectral analysis of the base shear forces indicates that the influence of vortex shedding on the across-wind base shear force is reduced by either increasing the amplitude or increasing the frequency of SOFs. The mean and instantaneous wind fields around the aeroelastic model in SOFs and smooth flow are compared, and the wake characteristics of the aeroelastic model in SOFs are analysed by dynamic mode decomposition. It is observed that when the frequency of SOFs is 1.5 times as large as the fundamental natural frequency of the aeroelastic model, the regular vortex shedding process is substantially affected. [ABSTRACT FROM AUTHOR]

To date, numerically simulating the Fluid–Solid Interaction (FSI) and the entire process of host rock damage and water inrush involved in tunnel construction relies intensively on hybrid methods of two or more numerical codes, which commonly encounter deficiency in learning, modelling and computation. A modified framework of Smoothed Particle Hydrodynamics (SPH), the Coupled Discontinuous SPH (CDSPH) method, was developed to simulate cracking, contacting and large deformation of rock blocks, free surface flow and the FSI for water/mud inrush disasters in tunnel construction through water–rich stratums. The failed SPH particles were transformed to discontinuous particles and new contacts between these particles were formed to simulate the frictional slip and separation/compression between fracture walls. The improved SPH method was employed to a water inrush case of a tunnel and the simulation results indicate that the entire process of progressive rock damage, water inrush and flooding are precisely reproduced by the improved method. The greater kinematic viscosity of fluids and rock wall thickness can increase the flow velocity and hence increasing the impact pressure of floods, and the failure pattern of the rock wall changes from partial outburst to complete failure. Vulnerability analysis of the water inrush reveals a complete damage status for people, vehicles and Non-RC frame buildings, and a moderate to complete damage to RC frame buildings at the tunnel portal. This single code is capable of simulating the behaviour of rocks, fluids and their interactions in catastrophic disasters that is potentially applicable to a wide spectrum of surface and subsurface problems involving FSI. [ABSTRACT FROM AUTHOR]

As key elements in plenty of rotating machinery, the elastohydrodynamic performance of journal bearings should be carefully checked in light of the design and operating parameters considered. This first part of the current study aims to numerically analyse the operation of journal bearings under alignment conditions. In the fluid-solid interaction analysis conducted, the lubricant flow field is solved using the finite volume method. Based on finite elements strategy, a structural analysis is then implemented to the solid bearing using the pressure distribution computed earlier on its inner surface. A wide range of operating conditions has been considered including the eccentricity ratio (0.1≤ε≤0.9), bearing length-diameter ratio (0.8≤L/D≤2), and rotation speed (4,000≤N≤10,000 rpm). Three principal categories of operational quantities have inspected, namely; the lubricant pressure distribution, overall performance parameters, and structural aftereffects. Among all the parameters examined, the eccentricity ratio is the most influential one on the performance of journal bearings. As it increases with applying heavier loads, a significant rise occurs in each of the friction force, power loss, stress levels, and deformation on the inner surface of the bearing. The bearing length and rotation speed, on the other hand, affect the bearing performance as well, but to a less extent.

Background: Carotid plaque morphology and tissue composition help assess risk stratification of stroke events. Many post-processing image techniques based on CT and MR images have been widely used in related research, such as image segmentation, 3D reconstruction, and computer fluid dynamics. However, the criteria for the 3D numerical model of carotid plaque established by CT and MR angiographic image data remain open to questioning.Method: We accurately duplicated the geometry and simulated it using computer software to make a 3D numerical model. The initial images were obtained by CTA and TOF-MRA. MIMICS (Materialize’s interactive medical image control system) software was used to process the images to generate three-dimensional solid models of blood vessels and plaques. The subsequent output was exported to the ANSYS software to generate finite element simulation results for the further hemodynamic study.Results: The 3D models of carotid plaque of TOF-MRA and CTA were simulated by using computer software. CTA has a high-density resolution for carotid plaque, the boundary of the CTA image is obvious, and the main component of which is a calcified tissue. However, the density resolution of TOF-MRA for the carotid plaque and carotid artery was not as good as that of CTA. The results show that there is a large deviation between the TOF-MRA and CTA 3D model of plaque in the carotid artery due to the unclear recognition of plaque boundary during 3D reconstruction, and this can further affect the simulation results of hemodynamics.Conclusion: In this study, two-dimensional images and three-dimensional models of carotid plaques obtained by two angiographic techniques were compared. The potential of these two imaging methods in clinical diagnosis and fluid dynamics of carotid plaque was evaluated, and the selectivity of image post-processing analysis to original medical image acquisition was revealed.

The aim of the present paper is the study of interaction of the abrupt wave with vertical and inclined rectangular obstacles. For this purpose, in the first step, two experiments have been done. The tests were performed with smooth rectangular cross-section channels, and related data were extracted using digital image processing. Flow behavior was recorded with one adjacent CCD camera through the glass walls of the entire downstream channel. In the second step, the numerical study has been done by a mesh-free particle Lagrangian method (Incompressible Smoothed Particle Hydrodynamics, ISPH) and a mesh-based Eulerian method (Finite Volume Method with Volume of Fluid surface tracking approach, FV-VOF). The capabilities of the numerical methods in simulation of the sudden variations free surface flows have been assessed. A comparison between the computed results and the experimental data shows that both numerical models simulate the mentioned flows with reasonable accuracy. [ABSTRACT FROM AUTHOR]

Background: Carotid plaque morphology and tissue composition help assess risk stratification of stroke events. Many post-processing image techniques based on CT and MR images have been widely used in related research, such as image segmentation, 3D reconstruction, and computer fluid dynamics. However, the criteria for the 3D numerical model of carotid plaque established by CT and MR angiographic image data remain open to questioning. Method: We accurately duplicated the geometry and simulated it using computer software to make a 3D numerical model. The initial images were obtained by CTA and TOF-MRA. MIMICS (Materialize's interactive medical image control system) software was used to process the images to generate three-dimensional solid models of blood vessels and plaques. The subsequent output was exported to the ANSYS software to generate finite element simulation results for the further hemodynamic study. Results: The 3D models of carotid plaque of TOF-MRA and CTA were simulated by using computer software. CTA has a high-density resolution for carotid plaque, the boundary of the CTA image is obvious, and the main component of which is a calcified tissue. However, the density resolution of TOF-MRA for the carotid plaque and carotid artery was not as good as that of CTA. The results show that there is a large deviation between the TOF-MRA and CTA 3D model of plaque in the carotid artery due to the unclear recognition of plaque boundary during 3D reconstruction, and this can further affect the simulation results of hemodynamics. Conclusion: In this study, two-dimensional images and three-dimensional models of carotid plaques obtained by two angiographic techniques were compared. The potential of these two imaging methods in clinical diagnosis and fluid dynamics of carotid plaque was evaluated, and the selectivity of image post-processing analysis to original medical image acquisition was revealed. [ABSTRACT FROM AUTHOR]

Interactions between an incompressible fluid passing through a flexible tube and the elastic wall is one of the strongly coupled fluid–solid interaction (FSI) problems frequently studied in the literature due to its research importance and wide range of applications. Although incompressible fluid is a prevalent model in many simulation studies, the assumption of incompressibility may not be appropriate in strongly coupled FSI problems. This paper narrowly aims to study the effect of the fluid compressibility on the wave propagation and fluid–solid interactions in a flexible tube. A partitioned FSI solver is used which employs a finite volume-based fluid solver. For the sake of comparison, both traditional incompressible (ico) and weakly compressible (wco) fluid models are used in an Arbitrary Lagrangian–Eulerian (ALE) formulation and a PISO-like algorithm is used to solve the unsteady flow equations on a collocated mesh. The solid part is modeled as a simple hyperelastic material obeying the St-Venant constitutive relation. Computational results show that not only use of the weakly compressible fluid model makes the FSI solver in this case more efficient, but also the incompressible fluid model may produce largely unrealistic computational results. Therefore, the use of the weakly compressible fluid model is suggested for strongly coupled FSI problems involving seemingly incompressible fluids such as water especially in cases where wave propagation in the solid plays an important role. Article highlights: Flow in a flexible tube is a strongly coupled FSI problem. The weakly compressible fluid model has computational merits in FSI problems. The incompressibility assumption for liquids leads to unrealistic results in some FSI cases. [ABSTRACT FROM AUTHOR]

Resin infusion is a pressure-gradient-driven composite manufacturing process in which the liquid resin is driven to flow through and fill in the void space of a porous composite preform prior to the heat treatment for resin solidification. It usually is a great challenge to design both the infusion system and the infusion process meeting the manufacturing requirements, especially for large-scale components of aircraft and wind turbine blades. Aiming at addressing the key concerns about flow fronts and air bubble entrapment, the present study proposes a modelling framework of the multiphase flow of resin and air in a dual scale porous medium, i.e. a composite preform. A finite strain formulation is discussed for the fluid–solid interaction during an infusion process. The present study bridges the gap between the microscopic observation and the macroscopic modelling by using the averaging method and first principle method, which sheds new light on the high-fidelity finite element modelling. [ABSTRACT FROM AUTHOR]

The fluid-solid interaction force has a decisive influence on the flow characteristics of micro-nano scale. Based on the dissipative particle dynamics (DPD) method, static and flow simulations of fluid in typical shale slits were carried out. The Lennard-Jones (LJ) potential function of 96X was applied to characterize the fluid-solid interaction force. The slit width ranged 3–10nm, the wall material was quartz, the fluid was n-hexane, and the driving force of the flow simulation ranged 1–20kcal/(mol·Å). The results show that due to the attraction of solid wall, the aggregation of fluid molecules near the wall was enhanced, fluid density there increased, and the diffusion coefficient there was significantly lower than that in the middle of the slit. The fluidity of the fluid near the wall is significantly reduced. In the flow model, when the fluid-solid interaction force was ignored, the flow profile was piston-like, and the velocity gradient at the edge of the slit was extremely large, showing the characteristics of slip flow. When the fluid-solid interaction force was taken into account, the velocity was reduced significantly, and the profile was parabolic. When the LJ96X was replaced by LJ126X potential function to characterize the fluid-solid interaction force, the attractive force from the wall on the fluid near the wall decreased, the fluidity was enhanced, and the velocity profile increased. When the conservative force parameter of fluid was changed, enhancing the wettability of oil phase, the affinity between fluid and solid was increased, and the velocity profile was reduced. [ABSTRACT FROM AUTHOR]

In order to study the variation of vortices and heat transfer enhancement characteristics of piezoelectric vibrating cantilever in liquid-cooled channels, the effects of fluid density and viscosity, mainstream velocity, and excitation voltage on vortices were analyzed. The theoretical and numerical simulation of piezoelectric vortices was carried out by using fluid-solid coupling method. On the basis of hydrodynamic function considering the additional effect of liquid viscosity and density on piezoelectric vibrator, the vortex structure of piezoelectric vibrator was analyzed by panel method free-wake model. It is found that the larger the density of the liquid, the smaller the vortex shedding strength and the radius of the core. The larger the viscosity of the liquid, the easier to fully develop the vortex generated by the excitation. The increase of the mainstream flow velocity is beneficial to the development of the vortex structure and the increase of the vorticity intensity. Compared with the increase of the mainstream flow velocity, the excitation voltage is more conducive to the enhancement of the vorticity structure, then make it easier to mix hot and cold fluids, thus enhancing heat transfer. [ABSTRACT FROM AUTHOR]