Two-way Fluid Structure Interaction Simulation Research Articles

Study on the influence mechanism of elastic appendage on the longitudinal stability of high-speed planing craft

Aiming at the problem of porpoising during high-speed navigation of planing crafts, this study designed a localized elastic appendage installed in the high-pressure area of the boat bottom, which can improve the longitudinal stability of the planing craft through its passive deformation. The ship model towing test and numerical simulation of rigid model (RM) and local elastic model (LEM) are carried out under still water conditions. The flow field calculation of RM based on CFD and the two-way fluid-structure interaction simulation of LEM based on CFD-FEM are all in good agreement with the experimental data. The test and numerical results indicate that in the speed range of 1–11 m/s, the maximum deformation of the LEM elastic appendage can approach 4 mm. There is an obvious improvement in longitudinal stability following deformation. The stable speed range is increased by 1.2 times and the trim angle of LEM is reduced by a maximum of 15% when compared to RM at the same speed. In terms of resistance, RM and LEM exhibit almost identical characteristics. Based on the details of flow field and the pressure distribution obtained by the numerical simulation, the mechanical properties of the planing craft after the deformation of the local elastic appendage have been analyzed, which provides a new design idea for the planing craft to improve the longitudinal stability.

Efficient two-way fluid–structure interaction simulation for performance prediction of pressure-compensating emitter

Drip irrigation using a high-performance pressure-compensating (PC) emitter is one of the essential components for precision agriculture, and it is necessary to accurately predict its performance prior to design. In this study, an efficient two-way fluid–structure interaction (FSI) simulation model was developed and verified through an enlarged model experiment. The computational fluid dynamics (CFD) and computational solid mechanics (CSM) models of the FSI simulation were systematically verified, and a calibration method for the overestimated flow rate in the re-rising range was applied. The CFD model was determined to be the shear stress transport turbulence model, and the CSM model was determined to be the Ogden hyperelastic model for the PC emitter. The minimum prediction error for the flow rate was 7.93%, which was within 10% for all cases. The simulation model demonstrated its efficiency by analysing the performance of a single PC emitter with an average total analysis time of 18.6 h. In addition, by comparing various cases according to the design parameters, it is considered that the hardness of the diaphragm has a significant impact on the design of low-pressure PC emitters. The simulation model of this study can accurately predict the performance of PC emitter under specific conditions, yet improvement of simulation model is required to be applied in design optimisation. Future studies may benefit from combining an improved FSI simulation with a surrogate model to further enhance optimisation efforts.

Wind-Induced Response Assessment of CAARC Building Based on LBM and FSI Simulation

It is very important for the wind-resistant design of high-rise buildings to assess wind-induced vibrations efficiently. The Lattice Boltzmann Method-based Large Eddy Simulation and Fluid–Structure Interaction techniques are used to identify the surface wind pressure and wind-induced dynamic response of a CAARC standard high-rise building. Compared with wind tunnel tests, a detailed analysis of the accuracy of simulated wind pressures and base moments of the CAARC model are discussed under multiple wind direction angles. The differences between one-way and two-way Fluid–Structure Interaction simulations are compared under two different reduced wind velocities. The research results show that the simulated mean surface wind pressures of building under seven wind direction conditions have an error within 15% compared to probe measurements, and the average and root mean square base bending moments agree well with the wind tunnel tests. The top transverse wind-induced vibrations of the buildings are significantly larger when the reduced wind velocity reaches 4.6, indicating that aerodynamic damping effects on structural responses should not be overlooked. The research findings of this article provide valuable technical references for the application of LBM methods in the wind load effect assessments of high-rise buildings.

Numerical Simulation and Validation of Flow-Induced Vibration of the Specific Rod under Elastic Supports using One-Way Fluid-Solid Interaction

The vibration induced by the cooling fluid flow around the fuel rods in the fuel Assembly of nuclear reactors causes the rods to be destroyed and eventually leak due to the fretting wear in the place of contact with their supports for a long time. In this paper, the vibration caused by axial fluid flow around a specific fuel rod under elastic supports is numerically simulated. In this study, the fluid flow is modeled using the Large Eddy Simulation (LES) turbulence model in the FLUENT software. The fluid-structure interaction is also modeled using the ANSYS coupling system. To validate the implemented numerical model, the test results of the reported brass rod vibration similar to the studied problem in this research are used. Due to the long execution time of the two-way fluid-structure interaction simulations with a high grid number, the one-way fluid-structure interaction method is proposed. The results of simulations show that the one-way fluid-structure interaction method can be used in cases where the vibration amplitude of the structure is less than the height of the viscous sub-layer. Also, this method reduces the simulation time by 80%. Finally, the results of the flow-induced vibration simulation of the fuel rod show that the vibration range of the fuel rod will increase by 20 times if the contact of the elastic supports with the rod is lost, which will lead to the intensification of the wear caused by the rod oscillation. Also, the main natural frequency of the rod decreases when the rod loses contact with the supports and falls within the range of the reactor excitation frequency, i.e. 0 to 50 Hz, which should be avoided.

Prediction of Thermoacoustic Instability and Fluid–Structure Interactions for Gas Turbine Combustor

Abstract This work simulates a laboratory-scale three-dimensional methane/air burner, which features a bluff body stabilized, lean partially premixed flame experiencing strong limit cycle oscillations. A thin steel liner is installed around the combustion chamber, which heavily interacts with the flow field and produces large amplitude structural deformation via fluid–structure interaction (FSI). An unsteady Reynolds averaged Navier–Stokes (URANS) approach uses the shear stress transport (SST) turbulence model and a flamelet generated manifold (FGM) combustion model to predict the thermoacoustic oscillations in the turbulent reacting flow. The solver also has a built-in finite element structure model, which solves the structural governing equations simultaneously with the computational fluid dynamics (CFD)-computed, finite volume flow equations. This way, a fully coupled, two-way FSI simulation can be performed to predict the thermoacoustic instabilities and the associated solid deformations in the burner. Overall, the predicted strongest pressure oscillation and wall displacement modes (frequency and amplitude) are all in good agreement with the experimental data across different operating conditions. The established workflow may support realistic gas turbine combustor design and prognosis.

Fluidelastic instability research of tube bundles by a two-way fluid-structure interaction simulation

Fluidelastic instability (FEI) could cause serious damage to the tube bundle, and streamwise FEI has attracted more attention in recent years. Water tunnel experiments have been conducted to investigate streamwise and transverse FEI in a parallel triangular tube bundle with a single elastic tube in center. RMS displacement-reduced velocity relationship diagram, vibration time-history curve and frequency spectrum response in streamwise and transverse directions are obtained. A Two-way fluid-structure simulation method was developed to calculate the streamwise and transverse FEI. The motion of the elastic tube was controlled by a User-Defined Function (UDF) coupled with dynamic mesh. The FEI tendency of simulation is consistent with experiment results but the values of predicted critical reduced velocities are more conservative. The process of FEI was analyzed. Finally, the model was extended to explore the effect of pitch diameter ratio, elastic tube arrangement and natural frequency ratio of streamwise and transverse.

Reconstruction of 3D Porous Geometry for Coupled FEM-CFD Simulation

Porous materials can be found in numerous areas of life (e. g., applied science, material science), however, the simulation of the fluid flow and transport phenomena through porous media is a significant challenge nowadays. Numerical simulations can help to analyze and understand physical processes and different phenomena in the porous structure, as well as to determine certain parameters that are difficult or impossible to measure directly or can only be determined by expensive and time-consuming experiments. The basic condition for the numerical simulations is the 3D geometric model of the porous material sample, which is the input parameter of the simulation. For this reason, geometry reconstruction is highly critical for pore-scale analysis. This paper introduces a complex process for the preparation of the microstructure's geometry in connection with a coupled FEM-CFD two-way fluid-structure interaction simulation. Micro-CT has been successfully applied to reconstruct both the fluid and solid phases of the used porous material.

Slamming and green water loads on a ship sailing in regular waves predicted by a coupled CFD–FEA approach

A numerical simulation method is presented by integrating Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) solvers to predict ship wave loads and slamming loads taking into account hydroelastic effects. The interest of this study mainly lies in the slamming and green water pressures acting on a flexible ship investigated by the coupled CFD–FEA method. Firstly, verification and sensitivity analysis of the wave loads and slamming pressures on the S175 containership evaluated by the coupled CFD–FEA method is conducted by comparing the results using different mesh sizes and time step schemes. Discussion on the effect of hydroelasticity on impact pressures is also conducted. Then a comprehensive analysis on the global motions, wave loads, slamming and green water pressures of the ship in different regular wave conditions is undertaken. Finally, a simplified bow flare and bottom slamming pressure estimation method based on the seakeeping data of incident wave and ship global motions are proposed, which can reduce the computational burden of the two-way fluid-structure interaction simulations when impact pressure is concerned.

Comparison between an uncoupled one-way and two-way fluid structure interaction simulation on a super-tall slender structure

This paper presents a comprehensive analysis on a super-tall structure where a numerical approach is used to measure its structural response when subjected to turbulent wind. The aim of this study is to provide a feasible alternate approach, to the experimental multi-degree of freedom (MDOF) aeroelastic wind tunnel tests, which are commonly used in industry to estimate structural responses of super-tall structures. An innovative and time-efficient uncoupled one-way Fluid-Structure Interaction (FSI) simulation technique was used to measure the structural response. This novel method was evaluated against a commercially available two-way FSI analysis technique and validated with an experimental MDOF aeroelastic model. It is shown that the uncoupled one-way FSI analysis is capable of estimating structural responses and provides similar numerical accuracy to that of the experimental response. This performance was achieved in a total of 74clock hours which accounts for the CFD simulation and transient structural analysis calculated for eighteen different structural configurations. In comparison, the two-way FSI analysis, which uses a commercial code, took 4800clock hours to calculate for six configurations. The uncoupled one-way FSI technique also provided good correlations with experimentally observed trends such as vortex-induced resonance. In comparison the two-way FSI simulation was not as accurate due to the practical limitations (such as mesh size) that needed to be introduced in order to obtain results within a feasible time frame. Finally through validation, it is demonstrated that the proposed uncoupled one-way FSI analysis technique can provide accurate results at a feasible cost.

The effect of the entry and re-entry size in the aortic dissection: a two-way fluid-structure interaction simulation.

Aortic dissection (AD) is one of the most catastrophic cardiovascular diseases. AD occurs when a layer inside the aorta is disrupted and gives rise to the formation of a true lumen and a false lumen. These lumens can be connected through tears in the intimal flap which are known as entries. Despite being known for about two centuries, the effects of many factors on the morbidity and mortality of this disease are still unknown. As the blood interaction with the aorta is crucial in the severity and the progression of the aortic dissection, a biomechanical approach is chosen to investigate the influence of different morphologies on the severity of this disease. Using the finite element method (FEM) and the fluid-structure interaction (FSI) approach, we have evaluated the blood flow characteristics along the diseased aorta, in conjunction with the deformation of the aortic wall. In this study, an idealized geometry of a dissected descending aorta (type B) with two entries has been studied. The values for the diameter of the entry tear were chosen to be 5 mm and 10 mm. Therefore, a total of four conditions were investigated. According to our results, the retrograde flow through the proximal tear is dependent on the size of the distal re-entry and vice versa. Our results revealed that when both entry and re-entry tears are 10 mm in diameter, the flow passes through the true and false lumens with smaller resistance, resulting in a smaller flutter of the intimal flap, and therefore more stable intimal flap. Major oscillation frequencies of 2.5 Hz and 7.4 Hz were observed for the oscillation of the intimal flap, and amplitudes of the waves with higher frequencies were negligible.

Research on negative-buoyancy autorotating-rotor autonomous underwater vehicles

The traditional neutral buoyancy underwater vehicle's carrying capacity is limited by space and displacement, making it difficult to meet the increasing demand for mission sensors. In light of this, a new type of negative-buoyancy autonomous underwater vehicle equipped with an autorotating rotor is proposed in this paper. Referring to the principle of air autorotating rotor, the negative-buoyancy autorotating-rotor autonomous underwater vehicle (NAAUV) adopts an autorotating rotor to provide lift and compensate for negative buoyancy, thus achieving effective navigation. Negative-buoyancy vehicles have greater carrying capacity, less use of buoyancy materials, smaller size of the vehicle, and lower resistance and energy consumption. To verify the working principle of NAAUV, a dynamic model is established and the navigation process of the vehicle is simulated. The results verify satisfactory navigation stability of the vehicle. Focus on the issue of the flapping and shimmy caused by inconsistent speeds of advancing and retreating rotor blades, the two-way fluid-structure interaction simulation method is adopted. As a result, flapping deformation and equivalent stress of the rotor are acquired. Because rotor material performance requirements are not strict, common metal materials can meet the requirements.

Numerical Simulation Calculation and Analysis of the Effect of Rocket and Duck Rudder on Its Aerodynamic Characteristics and Flexible Deformation

Based on inertia relief and CFD/CSD two-way coupling methods, the static aeroelasticity numerical simulation of a simply guided rocket with duck rudder actuator has been done, and the influence of duck rudder on aerodynamic characteristics and flexible deformation has been analyzed. Firstly, the lift, drag force and pitch moment coefficients, etc. had been calculated by using CFD method based on SST k-ω turbulence model, the error was less than 10 percent compared with the experimential data, and it verified the accuracy of fluid domain numerical method. Then, the two-way fluid-structure interaction simulation on the rocket and the contrastive analysis were done based on ANSYS Workbench multi-physics coupling simulation platform. The results show that duck rudder has a larger influence on rocket aerodynamic characteristics, by analysing the rocket aerodynamic coefficients under the conditions of without duck rudder, 0° rudder angle and 10° rudder angle, and it shows that the lift force and pitch moment coefficients change 5 to 30 percent with or without duck rudder and angle. Considering the influence of flexible deformation on aerodynamic coefficients, the flexible deformation has a more influence on the lift force and pitch moment coefficients, it reflects that the flexible deformation leads to the lift force coefficients smaller and pitch moment coefficients absolute value smaller, the maximum influence can reach to 5 to 10 percent. Meanwhile, the results show that the maximum deformation of rocket occurred in the middle of the rocket body, and the maximum equivalent stress occurred in the empennage of the rocket. Therefore, in the design of simply guided rockets, it’s very important to consider the influence of duck rudder on the aerodynamic characteristics and flexible deformation.

Numerical Investigation of Added Mass and Hydrodynamic Damping on a Blunt Trailing Edge Hydrofoil

Added mass and hydrodynamic damping play significant roles in fluid-structure interaction (FSI) in hydraulic turbines. Added mass can reduce natural frequencies, while hydrodynamic damping could result in a higher amplitude decay speed of the vibration. In order to quantify the added mass and hydrodynamic damping of a three-dimensional (3D) NACA 0009 hydrofoil with a blunt trailing edge, a two-way FSI simulation method was employed. The effects of grid scale, time-step, turbulence model, exciting force, and numerical damping on the calculation accuracy of the two-way FSI numerical simulation were analyzed in great detail through comparison with the previously published experimental data. Hydraulic force was obtained by using a transitional shear stress transport model at the flow region of the Reynolds number ReL = 0.2 × 106–2 × 106. The vortex shedding frequency, the natural frequency of the first-order bending mode in water, and the hydrodynamic damping ratio obtained from the numerical simulations agree well with the experimental data, with maximum deviations in 6.12%, 4.53%, and 8.82%, respectively. As the flow velocity increases, the natural frequency may not significantly change, while the added mass coefficient gradually increases, considering the effect of added stiffness. Above the first-order bending mode lock-in region, the results indicate that the first-order bending mode hydrodynamic damping ratio increases linearly with velocity. The present numerical achievements offer a higher level of accuracy for predicting the added mass and hydrodynamic damping characteristics of a hydrofoil.

Two-way fluid-structure interaction simulation for steady-state vibration of a slender rod using URANS and LES turbulence models

Abstract Anisotropic distribution of the turbulent kinetic energy and the near-field excitations are the main causes of the steady state Flow-Induced Vibration (FIV) which could lead to fretting wear damage in vertically arranged supported slender rods. In this article, a combined Computational Fluid Dynamics (CFD) and Computational Structural Mechanic (CSM) approach named two-way Fluid-Structure Interaction (FSI) is used to investigate the modal characteristics of a typical rod's vibration. Performance of an Unsteady Reynolds-Average Navier-Stokes (URANS) and Large Eddy Simulation (LES) turbulence models on asymmetric fluctuations of the flow field are investigated. Using the LES turbulence model, any large deformation damps into a weak oscillation which remains in the system. However, it is challenging to use LES in two-way FSI problems from fluid domain discretization point of view which is investigated in this article as the innovation. It is concluded that the near-wall meshes whiten the viscous sub-layer is of great importance to estimate the Root Mean Square (RMS) of FIV amplitude correctly as a significant fretting wear parameter otherwise it merely computes the frequency of FIV.

CFD analysis of energy harvesting from flow induced vibration of a circular cylinder with an attached free-to-rotate pentagram impeller

A new converter consisting of an elastically mounted circular cylinder and a free-to-rate pentagram impeller is proposed to harness hydrokinetic energy from water currents. The vibration energy of the cylinder and the rotation energy of the impeller are harvested simultaneously. The two-way fluid-structure interaction simulations are employed to investigate the vibration and rotation response of the converter. The simulated Reynolds number range is 14,000 < Re < 80,000, falling in the TrSL2 (transition of shear layer 2) and TrSL3 regimes. The results indicate that the vibration amplitude of the converter increases with increasing of the flow velocity, and the growth becomes faster at high reduced velocity (Ur). The presence and rotation of the impeller contribute to the hydrodynamic instability of the system at Ur ≥ 9, where the rotational direction is constantly changing. The hydrodynamic instability brings about a wider flow wake and unstable vortex shedding, resulting in the enhancement of vibration and the increase of power. For such a rotation symmetric structure, increasing the torsional friction does not play a significant role in suppressing the hydrodynamic instability. The estimated power generating capacity is sensitive to flow velocity and additional damping ratio. The average power efficiency is about 22.6%, and the power density for a 5D × 5D staggered configuration with ζharn of 0.031374 can reach 885.53 W/m3.

Simulation of air flow–yarn interaction inside the main nozzle of an air jet loom

The main nozzle of an air jet loom plays an essential role in the weft insertion process. This role involves sucking the weft yarn from the prewinder and launching it into the reed. Simulating the dynamic behavior of the weft yarn inside the main nozzle involves fluid–structure interaction (FSI). In this work, one-way and two-way FSI simulations of air flow–yarn interaction inside a main nozzle have been performed. A three-dimensional model of the flexible weft yarn, consisting of a chain of line segments, and a two-dimensional axisymmetric model of the supersonic flow have been developed and coupled to perform these simulations. The results of the simulations are compared quantitatively and qualitatively with experimental results. Good agreement has been found between the results of the two-way FSI simulations and the experiment. The coupled fluid and structure models provide an effective numerical tool to optimize the geometry of the main nozzle based on the calculated motion and speed of the weft yarn.

Importance of Physical and Physiological Parameters in Simulated Particle Transport in the Alveolar Zone of the Human Lung

The trajectory and deposition efficiency of micron-sized (1–5 µm) particles, inhaled into the pulmonary system, are accurately determined with the aid of a newly developed model and modified simulation techniques. This alveolar model, which has a simple but physiologically appropriate geometry, and the utilized fluid structure interaction (FSI) methods permit the precise simulation of tissue wall deformation and particle fluid interactions. The relation between tissue movement and airflow in the alveolated duct is solved by a two-way fluid structure interaction simulation technique, using ANSYS Workbench (Release 16.0, ANSYS INC., Pittsburgh, PA, USA, 2015). The dynamic transport of particles and their deposition are investigated as a function of aerodynamic particle size, tissue visco-elasticity, tidal breathing period, gravity orientation and particle–fluid interactions. It is found that the fluid flows and streamlines differ between the present flexible model and rigid models, and the two-way coupling particle trajectories vary relative to one-way particle coupling. In addition, the results indicate that modelling the two-way coupling particle system is important because the two-way discrete phase method (DPM) approach despite its complexity provides more extensive particle interactions and is more reliable than transport results from the one-way DPM approach. The substantial difference between the results of the two approaches is likely due to particle–fluid interactions, which re-suspend the sediment particles in the airway stream and hence pass from the current generation.

Aortic dissection simulation models for clinical support: fluid-structure interaction vs. rigid wall models.

BackgroundThe management and prognosis of aortic dissection (AD) is often challenging and the use of personalised computational models is being explored as a tool to improve clinical outcome. Including vessel wall motion in such simulations can provide more realistic and potentially accurate results, but requires significant additional computational resources, as well as expertise. With clinical translation as the final aim, trade-offs between complexity, speed and accuracy are inevitable. The present study explores whether modelling wall motion is worth the additional expense in the case of AD, by carrying out fluid-structure interaction (FSI) simulations based on a sample patient case.MethodsPatient-specific anatomical details were extracted from computed tomography images to provide the fluid domain, from which the vessel wall was extrapolated. Two-way fluid-structure interaction simulations were performed, with coupled Windkessel boundary conditions and hyperelastic wall properties. The blood was modelled using the Carreau-Yasuda viscosity model and turbulence was accounted for via a shear stress transport model. A simulation without wall motion (rigid wall) was carried out for comparison purposes.ResultsThe displacement of the vessel wall was comparable to reports from imaging studies in terms of intimal flap motion and contraction of the true lumen. Analysis of the haemodynamics around the proximal and distal false lumen in the FSI model showed complex flow structures caused by the expansion and contraction of the vessel wall. These flow patterns led to significantly different predictions of wall shear stress, particularly its oscillatory component, which were not captured by the rigid wall model.ConclusionsThrough comparison with imaging data, the results of the present study indicate that the fluid-structure interaction methodology employed herein is appropriate for simulations of aortic dissection. Regions of high wall shear stress were not significantly altered by the wall motion, however, certain collocated regions of low and oscillatory wall shear stress which may be critical for disease progression were only identified in the FSI simulation. We conclude that, if patient-tailored simulations of aortic dissection are to be used as an interventional planning tool, then the additional complexity, expertise and computational expense required to model wall motion is indeed justified.