Fluid-Structure Interaction Analysis on Pressure-Compensating Emitters

Key Words: Fluid-Structure Coupled Analysis(유체-구조연계해석), Low-Pressure Turbine(저압터빈), SweptbackWing(후퇴익), NASA Rotor 37초록: 본논문에서는, 운전조건에서의저압최종단블레이드에대하여약결합유체-구조연계해석기법을이용한해석이수행되었다. 저압터빈최종단에대한해석이전에경계조건에대한검증을위하여15도후퇴익과NASARotor 37을대상으로예비해석이수행되었다. 각각의해석결과들을기존문헌들과비교하였다. 15도후퇴익에대한안정상태와불안정상태에서동적FSI해석이수행되었다. 해석결과변위가일정한안정상태에비하여고속에서는0.05 초만에발산하는결과를산출하였다. NASA Rotor 37의정상상태해석결과를바탕으로정적·동적FSI해석을수행하여뒷전의변형크기에대하여정적FSI 결과와동적FSI간의차이가있음을확인하였다. 저압최종단블레이드의형상측정및동특성시험을바탕으로해석모델을생성하였다. 이를바탕으로, 운전조건에서저압최종단블레이드에대한정적유체-구조연계해석을성공적으로수행하였다.Abstract: In this study, a loosely coupled fluid-structure interaction (FSI) analysis was conducted for a low-pressure(LP) final-stage rotor blade. Preliminary FSI analyses of a 15° sweptback wing and a NASA Rotor 37 compressorblade were performed for verifying the boundary conditions. The results were compared with the established literaturesfor each model. The FSI analysis of the 15° sweptback wing was carried out under both stable and unstableconditions. The excessive deformation of the wing was observed within 0.05 s under the unstable condition which ishigher than the divergence speed of a wing compared with the stable condition. On the basis of the results of asteady-state study, an unsteady state FSI analysis was conducted for a NASA Rotor 37. Different deformations wereobserved at trailing edge of the blade in the static FSI and dynamic FSI analysis. A 3D FE model of a LP rotor wasgenerated from the span-wise section data. In order to develop a reasonable model, an impact test was performed andcompared to the FE model. Using this FE model, the steady-state FSI analysis was performed successfully.

Inflatable aerodynamic decelerators are being developed as a new technology for atmospheric reentry. Flexible aeroshells have been observed to deform under aerodynamic loads, and to investigate their behavior, fluid-structure interaction (FSI) analysis that considers the coupling between high enthalpy flow and structural flexibility is appropriate. This study investigated the FSI behavior of a flexible aeroshell in the supersonic regime, where compression effects are prominent, with the objective of elucidating the influence of structural deformation on the resulting aerodynamic forces. Numerical simulations were conducted with and without structural deformation under two angle-of-attack (AOA) conditions. The results showed that at non-zero AOA, asymmetric deformation of the structure, caused noticeable changes in the flow and aerodynamic forces. In contrast, at zero AOA, the influence of structural flexibility was relatively small. These findings indicate that FSI analysis is especially important for accurately evaluating flexible aeroshells in supersonic flows under inclined flight conditions.

Transcatheter aortic valve replacement (TAVR) is a minimally invasive procedure that provides an effective alternative to open-heart surgical valve replacement for treating advanced calcific aortic valve disease patients. However, complications, such as valve durability, device migration, paravalvular leakage (PVL), and thrombogenicity may lead to increased overall post-TAVR morbidity and mortality. A series of numerical studies involving a self-expandable TAVR valve were performed to evaluate these complications. Structural studies were performed with finite element (FE) analysis, followed by computational fluid dynamics (CFD) simulations, and fluid-structure interaction (FSI) analysis. The FE analysis was utilized to study the effect of TAVR valve implantation depth on valve anchorage in the Living Heart Human Model, which is capable of simulating beating heart during repeated cardiac cycles. The TAVR deployment cases where no valve migration was observed were then used to calculate the post-deployment thrombogenic potential via CFD simulations. FSI analysis followed to further assess the post-deployment TAVR hemodynamic performance for different implantation depths. The deployed valves PVL, geometric and effective orifice areas, and the leaflets structural and flow stress magnitudes were compared to determine the device optimal landing zone. The combined structural and hemodynamic analysis indicated that with the TAVR valve deployed at an aft ventricle position an optimal performance was achieved in the specific anatomy studied. Given the TAVR's rapid expansion to younger lower-risk patients, the comprehensive numerical methodology proposed here can potentially be used as a predictive tool for both procedural planning and valve design optimization to minimize the reported complications.

The use of very thin, subtle and light structures as an external part of buildings causes many problems related to wind induced vibration. Constructions of this type occur mostly as a part of roofs or design facades. The principal idea of this paper is to show dynamic response of triangular lamella exposed to wind gusts, which frequency is equal to the first natural frequency of the lamella. By the two-way software fluid-structure interaction (FSI) analysis, oscillation of the lamella was detected. The solution of two-way FSI analysis requires co-simulation between computational fluid dynamics and structural mechanics. In the simulation, it was essential to simulate conditions that if met, create resonant vibration of the lamella caused by vortex shedding on the leeward side of the structure. If the frequency of vortex shedding matches the resonance frequency of the structure, the structure begins to resonate and vibrates in harmonic oscillations driven by the energy of the flow. In this case, vibration rises and structure can be damaged or deformed permanently. For the long-term vibration, fatigue stress and subsequently fatigue failure is significant. By the usage of empirically derived equations, input data for the software simulation were obtained. It was important to consider mainly natural frequency of lamella, frequency of vortex shedding behind the structure and also correct properties of air such as wind speed, frequency of wind gusts, density of an air and Strouhal number. As a conclusion, dynamic response of lamella in the form of deformation and wind stream pattern depending on time is shown. It has been also shown that if the inputs are specified correctly to software simulation it is possible to analyse time history of many variables such as deformation, wind speed, and acceleration. By this method, it is possible to determine not only the maximum variables such as deformation or wind speed, but also its entire time history. In practice, it is therefore possible to create different design situations and, on their basis, design the lightweight non-bearing structures exposed to the wind.

It is known that damages to the subsea cables used for electric power transmission between islands and countries, including renewable energy from offshore wind power, current, tides, etc., cost much to restore, which causes social and economic losses. Various types of fishing rigs and anchors have been reported to be the greatest hazards to subsea cables. It is possible to design and construct a suitable protection facility for a subsea cable by precisely estimating the underwater behavior of such hazardous apparatuses. In this study, numerical simulations of the underwater behaviors of various hazardous apparatuses were carried out using fluid-structure interaction (FSI) analysis as a basic study to simulate the actual behavior phenomena of hazardous apparatuses in relation to a subsea cable. In addition, the underwater drop characteristics according to the types of hazardous apparatuses were compared. In order to verify the accuracy of the FSI analysis method used in this study, we compared the test results for underwater drops of a steel ball bearing. Stock anchors, stockless anchors, and rocket piles, which were actually reported to be the cases of damage to subsea cables along the southwest coast of Korea, were considered as the hazardous apparatuses for the numerical simulations. Each hazardous apparatus was generated by a Lagrangian model and coupled with the fluid domain idealized by the Eulerian equation to construct the three-dimensional FSI analysis model. The accuracy of the numerical simulation results was verified by comparing them with the analytical solutions, and the underwater drop characteristics according to the types of hazard apparatuses were compared.

Dynamic response considering fluid structure interaction (FSI) is crucial in many engineering fields and the numerical methods to solve the FSI problems are keenly demanded in engineering field. Generally coupled phenomena can be simulated in either monolithic or partitioned methods, however the application of FSI analysis are limited because of its calculation costs. The partitioned method is now focused because it can re-use the existing flow and structural analysis solver without elaborated modification and it gives the same accuracy when iterative coupling approach is taken. When the partitioned method combined with the existing flow and structure solver which can solve large-scale analysis model, it is expected to solve realistic three dimensional complex FSI problems in acceptable durations. In this work, the partitioned FSI analysis system are developed using existing flow and structure solvers. The system is applied to several validation models and accuracy and efficiency of the solver are shown.

A non-linear analysis procedure has been developed to investigate the plastic behavior of the divider (or partition) plate in Steam Generators (SG) of Pressurized Water Reactors (PWRs). The integrity of the divider plate in the primary channel head of a Steam Generator of a Pressurized Water Reactor has to be verified for a postulated loss of coolant accident (LOCA). Primary stresses due to differential pressure Δp have to be analyzed for faulted conditions. A static elastic-plastic finite element analysis for the divider plate was performed showing unrealistically high plastic deformation due to the high differential pressure loading resulting from the assumption of rigid walls in the fluid analysis. Therefore the LOCA is analyzed in a Fluid Structure Interaction Analysis (FSIA), representing the divider plate as a single degree of freedom system (SDOFS) acting like a piston. The present paper explains how the Δp across the plate was correlated with an equivalent displacement ve and how the mass of the plate is considered. In the FSIA a realistic dynamic response of the divider plate is considered now, with a significant reduction of differential pressure Δp. The analysis results proved the resistance of the divider plate with sufficient margin.

Effect of different sand filter underdrain designs on emitter clogging using reclaimed effluents

<div class="section abstract"><div class="htmlview paragraph">The present work is concentrated to study the effect of varying inlet pressures on the dynamics of the suction valve obtained from a hermetic reciprocating compressor. The effect of valve functioning on the efficiency of a compressor is highly acceptable. Rather than the delivery valve, the suction valve has a significant impact on the compressor efficiency. The reed valve in a hermetic compressor is a cantilever type arrangement. The valve operates due to the pressure difference between the suction muffler and the cylinder. The numerical analysis which includes Fluid-structure interaction is used in the present study. The flow and structural domain employed in the present study are modelled with Solidworks 15.0. The fluid structure interaction analysis is a combination of ANSYS Fluent and ANSYS structural. These two are coupled with a system coupling in ANSYS Workbench 16.0. The numerical results obtained from the simulation are validated with the experimental data. The setup consists of a stainless steel reed valve taken from a Samsung model compressor which is attached to a fixed base. Air is taken as working medium and supplied to the valve for measuring the valve lift. The valve lift is measured with a strain gauge fitted on the valve near the fixed end. The results from both the experimental and numerical method are compared to 0.5 bar, and the results are in good agreement. Various parameters like valve deflection, stress on the valve, velocity vectors and pressure contours are plotted. Further, the analysis is carried out for varying pressure from 0.5 bar to 2 bar. Also, the material of the reed valve is changed to Sandvik Hiflex steel which is known for its high fatigue strength and the corresponding results are plotted.</div></div>

Analysis of fluid/structure interaction: Influence of silicon chip thickness in moulded packaging

An experimental analysis of fluid structure interaction on a flexible hydrofoil in various flow regimes including cavitating flow

New designs of low pressure turbines show optimized geometries of stator and rotor blading as well as reduced axial spacing between stator and rotor due to the main target of saving weight which is directly related to the fuel consumption of the aero engine. An important step during the realization process is to investigate altered excitation mechanism. For this purpose aero elastic investigations will be performed at the test rig of Graz University of Technology. In general for a serious prediction of vibration characteristics under operating conditions of any structure a detailed knowledge of the dynamic behavior is essential. In preparation of upcoming strain gauge vibration measurements in combination with a telemetry system of the low pressure turbine rotor blading, modal characteristics as well as a realistic estimation of blade deformation are mandatory. Within this paper different methods of evaluating modal characteristic numerical as well as experimental such as impact hammer and shaker tests, respectively are presented. Numerical investigations show different models and mathematical contact formulation and should provide a better understanding for using correct contact models additionally. When comparing numerical with experimental results a prediction of an optimal strain gauge setup for vibration measurements as well as a simplified numerical model for further aero elastic investigations, such as fluid structure interaction analysis (FSI), complete previous investigations. In order to set up the telemetry system the knowledge of blade deformation at operating conditions is of particular importance. Therefore finally in this paper a 1-way FSI coupling is presented.

ABSTRACTIn this study, an improved fluid–structure interaction (FSI) analysis method is developed for a flapping wing. A co-rotational (CR) shell element is developed for its structural analysis. Further, a relevant non-linear dynamic formulation is developed based on the CR framework. Three-dimensional preconditioned Navier–Stokes equations are employed for its fluid analysis. An implicit coupling scheme is employed to combine the structural and fluid analyses. An explicit investigation of a 3D plunging wing is conducted using this FSI analysis method. A further investigation of this plunging wing is performed in relation to its operating condition. In addition, the relation between the wing’s aerodynamic performance and plunging motion is investigated.

Fluid–structure interaction analysis on the effect of chip stacking in a 3D integrated circuit package with through-silicon vias during plastic encapsulation

Numerical analysis of rubber dams using fluid–structure interactions