Consideration Of Fluid-structure Interaction Research Articles

Deep learning-based analysis to identify fluid-structure interaction effects during the response of blast-loaded plates

Blast events within urban areas in recent decades necessitate that protective design is no longer reserved for military installations. Modern civil infrastructure composed of light-weight, flexible materials has introduced the consideration of fluid-structure interaction (FSI) effects in blast-resistant design. While the action of blast loading on massive, rigid structures in military fortifications is well established, assessment of FSI effects is, at present, only possible through computationally expensive coupled simulations. In this study, a data-driven approach is proposed to assist in the identification of the blast-loading scenarios for which FSI effects play a significant role. A series of feed-forward deep neural networks (DNNs) were designed to learn weighted associations between characteristics of uncoupled simulations and a correction factor determined by the out-of-plane displacement arising from FSI effects in corresponding coupled simulations. The DNNs were trained, validated and tested on simulation results of various blast-loading conditions and material parameters for metallic target plates. DNNs exposed to mass-per-unit-area, identified as an influential factor in quantifying FSI effects, generalised well across a range of unseen data. The explainability approach was used to highlight the driving parameters of FSI effect predictions which further evidenced the findings. The ability to provide quick assessments of FSI influence may serve to identify opportunities to exploit FSI effects for improved structural integrity of light-weight protective structures where the use of uncoupled numerical models is currently limited.

Mechanical research on aerostatic guideways in consideration of fluid-structure interaction

PurposeThe purpose of this paper is to study the mechanical properties of aerostatic guideway taking the structural deformation into account, and further improve the calculation method of guideway.Design/methodology/approachA theoretical model of fluid-structure interaction for the numerical simulation was established and mechanical properties of the aerostatic guideway with porous restrictors were solved based on computational fluid dynamics. The deformation law of the guideway with different materials and gas-film thicknesses was revealed, and its static and dynamic characteristic curves were obtained.FindingsThe results indicate that ceramics as the material of guideways exhibit good applicability due to the small deformation, the quick dynamic response and the relatively light weight. The rational initial gas-film of guideway is recommended.Originality/valueThe present work can provide ideas for the design and optimization of aerostatic guideways.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2019-0288

Analytical treatment for vibration analysis of partially cracked orthotropic and FGM submerged cylindrical shell with consideration of fluid-structure interaction

Analytical solution for vibration analysis of orthotropic and FGM submerged cylindrical shell containing a surface crack of variable angular orientation is presented in this work. The governing equations in terms of transverse deflection of cracked-submerged shell have been derived using classical shell theory. The fluid forces associated with its inertial effects are added in the governing differential equation to incorporate the fluid–structure interaction effect. The line spring model (LSM) is used to formulate the crack coefficients to accommodate the effect of crack in the governing equation. Furthermore, the governing equation is solved using Donell–Mushtari–Vlasov (DMV) theory to get the fundamental frequency. The results are presented for frequency by giving the input parameters as crack length, crack orientation, and shell’s physical properties such as radius, thickness, and length of the shell. Communicated by Wei-Chau Xie

Seismic performance of base-isolated AP1000 shield building with consideration of fluid-structure interaction

Seismically-induced FSI effect on dynamic responses of AP1000 shield building with base isolation is focused in this study using numerical simualtion. The numerical model is firstly validated by comparison with existing experimental results, which is capable of simulating dynamic behaviors of the water partially-filled shield building with seismic isolation using high damping rubber (HDR) bearings. The influences of FSI on seismic performance of the base-isolated and base-fixed AP1000 shield building with various water levels and on the corresponding isolation effectiveness are comparatively explored in details. Results show that base isolation can reduce the fundamental frequency of the shield building and make it close to water sloshing frequency. It is necessary to ensure an reasonable isolation design to keep the fundamental frequency away from the sloshing frequency and then to avoid the water resonance. Seismic isolation can offer a substantial benefit for the earthquake-resistant design of the shield building even filled with different levels of water, because the structural primary resonance is effectively transformed to the sub-resonance by application of base isolation. Dynamic responses of base-isolated models are influenced significantly by FSI and an optimal water level ratio of 0.8 is suggested to achieve excellent seismic performance for such structures.

The role of fluid-structure interaction for safety and life time prediction in hydraulic machinery

Reliable assessments of dynamic phenomena in hydraulic machinery require the consideration of fluid-structure interaction (FSI) if natural frequencies or damping properties of submerged structural parts clearly change due to the surrounding water or if the interaction may cause instabilities. Exemplarily, three different applications of strongly coupled FSI are presented which all have a high impact on operational safety or dynamic stresses and fatigue life. At first, flow induced damping effects at a Francis runner exhibit a strong dependency on operating condition and mode shape. Secondly, if a rotating disc is submerged, a splitting of natural frequencies is observed for mode shapes with different spinning direction. Finally, a hydroelastic instabilitiy is identified in a bypass valve at small opening.

On numerical simulation of fuel assembly bow in pressurized water reactors

Fuel assembly bow in pressurized water reactor cores is largely triggered by lateral hydraulic forces together with creep processes generated by neutron flux. A detailed understanding of the flow induced bow behaviour is, therefore, an important issue. The experimental feedbacks and laboratory tests on fuel assembly bow show that it is characterized to a high degree by fluid–structure interaction (FSI) effects, therefore, consideration of FSI is essential and indispensable in full comprehension of the bow mechanism.In the present study, coupled computational fluid dynamics (CFD) and finite element simulations are introduced, calculating fuel assembly deformation under different conditions as a quasi-stationary phenomenon. The aim has been, on the one hand, to develop such a simplified fuel assembly CFD model, which allows set up of fuel assembly rows without loosing its main hydraulic characteristic; on the other hand, to investigate the bow pattern of a given fuel assembly row under different boundary conditions. The former one has been achieved by comparing bow shapes obtained with different fuel assembly (spacer grid) modelling approaches and mesh resolutions with experimental data.In the second part of the paper a row model containing 7.5 fuel assemblies is introduced, investigating the effect of flow distribution at inlet and outlet boundary regions on fuel assembly bow behaviour. The post processing has been focused on the bow pattern, lateral hydraulic forces, and horizontal flow distribution. The results have revealed importance of consideration of FSI, and that an inhomogeneous inlet/outlet flow condition causes significant ‘C’ shaped deformation of fuel assemblies towards the core shroud. The important effect of the core shroud has been also shown.

Hydrodynamic modeling of cochlea and numerical simulation for cochlear traveling wave with consideration of fluid-structure interaction

The cochlea is an important structure in the hearing system of humanity. Its unique structure enables the sensibility to the sound waves of varied frequencies. The widely accepted model of the cochlea is expressed as a long tube longitudinally divided by a membrane named the Basilar Membrane (BM), into two fluid-filled channels. Based on various assumptions for the cochlear fluid and structure, simplified mathematical and mechanical cochlear models were developed to help to understand the mechanism of the complex coupled system in the past decades. This paper proposes a hydrodynamic numerical cochlear model with consideration of the Fluid-Structure Interaction (FSI). In this model, the cochlear lymph is considered as in a Newtonian viscous fluid, and the basilar membrane is modeled as a composite structure. The traveling wave is simulated. Also focusing on the pressure in the fluid field, the results are compared with studies of Peterson and Bogert, where it was assumed that the slow compressive waves are traveling along the BM. Furthermore, the transmitting time of the cochlear traveling wave is also discussed.

Study on hull vibration and underwater radiation noise induced by propeller excitation considering shafting alignment

The recent increases in the number, size, speed and horsepower of commercial ships led the ocean ambient noise levels at low frequencies increased. Accordingly, the analysis of ship hull vibration control and noise reduction needs to be paid more attention now. In this paper, a finite element model of bulk carrier including shafting is built. Considering the shafting alignment, the vibration and underwater radiation noise characteristics of hull structure caused by propeller excite force are calculated. Finite element method (FEM) is employed to simulate the vibration response of the hull structure due to the propeller excitation in consideration of fluid-structure interaction. Then the outer surface of the finite element model is treated as a boundary element model. Finite element solutions of the hull surface vibratory velocity are further used as velocity boundary condition of the hull boundary element model for consequent underwater radiated noise calculation with boundary element method (BEM). In addition, the characteristics of transfer force and radiated sound power of hull structure are obtained. Comparing with the numerical results of considering shafting alignment and without, the effect of shafting alignment on propeller-induced ship hull vibration and underwater radiation noise is analyzed.

Investigation of Ship Structural Vibration and Underwater Radiation Noise

Underwater radiation noise is a very important factor for most ships, such as fishing boats, warships, and so forth. The magnitude of its energy depends on the vibration of the hull in contact with water. The vibration of the hull caused by the power plant, while the vessel is cruising, is the dominant source of underwater radiation noise, which is the subject of our investigation. In this paper, the coupled finite element/boundary element method is used to investigate ship structural vibration and underwater radiation noise. The finite element method (FEM) is employed to analyze modes and vibration responses of an entire ship for different kinds of excitations in consideration of fluid-structure interaction. The boundary element method (BEM) is used to analyze the underwater radiation noise. A FEM model is first constructed by using 30 geometric parameters and five kinds of finite elements. Then, the reduced matrix method is used to eliminate the local modes in order to obtain the overall bending and torsional modes of the ship. Last, vibration displacements of the hull are treated as the velocity boundary condition of BEM to calculate underwater radiation noise. Numerical results show thatthe calculated sound-pressure levels of underwater radiation noise are in a good agreement with experimentally measured results;although the vibration isolator is used, the propulsion diesel engine is the dominant source of the underwater radiation noise among all machines in the engine room and the maximum sound-pressure levels increase as the sailing speed of the ship increases;the underwater radiation noise of the ship with gearbox excitation is greater than that of the ship with diesel generator set excitation, which should be noticed by the ship designers during the design stage.

Vibration analysis of the pressure vessel internals of WWER-1000 type reactors with consideration of fluid-structure interaction

Vibration analysis of the pressure vessel internals of WWER-1000 type reactors with consideration of fluid-structure interaction

SOUND ENERGY FLOW IN THE ACOUSTIC NEAR FIELD OF A VIBRATING PLATE

The sound radiation from a vibrating structure in water is investigated. The radiation depends on fluid boundaries, the geometry of structure, and associated mode shapes generated by driving forces on the structure. In the lower frequency range, the structure can be divided into regions having high and low radiation. These regions represent a distribution of sources and sinks of noise. The sound pressure level in the fluid domain and the velocity field is determined by using a boundary element method with input data of surface velocities obtained from the modal analysis of from a finite element calculation. A consideration of fluid structure interaction is possible. Alternatively, noise sources can be identified by intensity vector measurements in the acoustic near field. For a comparison of these approaches, the sound radiation from a vibrating plate calculated by the boundary element method (BEM) was compared with the results obtained by a superposition of pulsating spheres. The second approach is based on analytical results and the acoustic near field can be described in terms of energy flow.