A lot of work has gone into the study of valveless micropumps for various applications. However, the complex fluid-structure interactional physics and associated phenomena such as cavitation affects the characterizati...
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A lot of work has gone into the study of valveless micropumps for various applications. However, the complex fluid-structure interactional physics and associated phenomena such as cavitation affects the characterization of valveless micropumps, for applying them reliably in any real-time applications. This paper presents a method of characterization of valveless micropump performance through dynamic measurement of chamber pressure. Experimental investigation has been carried out to study the micropump behavior through pressure measurement under both cavitation and non-cavitation conditions, and the results show that this technique is useful for the characterization of micropump.
The micropressure wave radiated from a tunnel exit is one of the environmental problems which can be investigated from the temporal pressure gradient of the compression wave. The effects of inclined portals on the ini...
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The micropressure wave radiated from a tunnel exit is one of the environmental problems which can be investigated from the temporal pressure gradient of the compression wave. The effects of inclined portals on the initial compression wave, specifically the maximum temporal pressure gradient, are numerically studied by solving the flow field during a high-speed train nose entering a tunnel, using the unsteady three-dimensional (3D) Euler equations. After mesh independency and temporal sensitivity tests of the numerical method, validations are conducted by comparing the numerical results with experimental and numerical data. The temporal gradients of pressure wavefront are parametrically investigated for different combinations among the train speed, the blockage ratio of the train to tunnel, and inclination angle of the tunnel entrance. The numerical results show a negligible influence of train Mach number or blockage ratio on the normalized pressure gradient and noticeable effects of inclination angle, location of the train with respect to the median line of a double-tracked tunnel (DT), and the profile of train nose. Based on the numerical results, an empirical formula is proposed to predict the relationship between the maximum pressure gradient and the inclination angle of tunnel entrance.
The use of a membrane to mitigate the extreme pressure loads on the roof of a surface-mounted prism is investigated. The fluid-structure interaction problem is solved by coupling the unsteady Navier-Stokes equation wi...
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The use of a membrane to mitigate the extreme pressure loads on the roof of a surface-mounted prism is investigated. The fluid-structure interaction problem is solved by coupling the unsteady Navier-Stokes equation with the membrane equation. The minimum number of membrane modes required for the solution is determined through a convergence study. The results show that this passive control technique can be used to reduce the extreme pressure coefficients by approximately 25%. This reduction is explained by investigating the effects of the membrane on the flow field. (C) 2014 American Society of Civil Engineers.
In the present study, a finite element formulation is presented to investigate vibration response of elastic plates in contact with a fluid medium. The fluid is assumed to be incompressible and inviscid, and the imper...
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In the present study, a finite element formulation is presented to investigate vibration response of elastic plates in contact with a fluid medium. The fluid is assumed to be incompressible and inviscid, and the impermeability condition of the plate is taken into account. The classical plate theory (CPT), first-order shear deformation plate theory (FSDT), and Reddy third-order shear deformation plate theory (RSDT) are considered for the kinematic description of the solid medium and the simplified Navier-Stokes equations are used as the governing equations for the fluid medium. For each plate theory, a coupled set of finite element equations is derived. The effect of the fluid pressure is considered as an added mass and its effect on natural frequencies and mode shapes is investigated through several numerical simulations by varying the boundary conditions.
Engineers have started to develop ways to decrease noise radiation. Structural-acoustic design sensitivity analysis can provide information on how changes in design variable affect the radiated acoustic performance. A...
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Engineers have started to develop ways to decrease noise radiation. Structural-acoustic design sensitivity analysis can provide information on how changes in design variable affect the radiated acoustic performance. As such, it is an important step in the structural-acoustic design and in optimization processes. For thin structures immersed in water, a full interaction between the structural domain and the fluid domain needs to be taken into account. In this work, the finite element method is used to model the structure parts and the boundary element method is applied to the exterior acoustic problem. The formula of the sound pressure sensitivity based on the direct differentiation method is presented. The design variable can be chosen as the material parameters, structure and fluid parameters, such as the fluid density, structural density, Poisson's ratio, Young's modulus, structural shape size and so on. Numerical examples are presented to demonstrate the validity of the proposed algorithm. Different types elements are used for the numerical solution, and the performance of different types of FE/BE element is presented and compared.
This work reports results related to the EU-FP7-HRC-Power project aiming at developing micro-meso hybrid sources of power. One of the goals of the project is to achieve surface temperatures up to more than 1000 K, wit...
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This work reports results related to the EU-FP7-HRC-Power project aiming at developing micro-meso hybrid sources of power. One of the goals of the project is to achieve surface temperatures up to more than 1000 K, with a T 100 K, in order to be compatible with a thermal/electrical conversion by thermo-photovoltaic cells. The authors investigate how to reach that goal adopting swirling chambers integrated in a thermally-conductive and emitting element. The converter consists of a small parallelepiped brick inside two separated swirling meso-combustion chambers, which heat up the parallelepiped, emitting material by the combustion of H-2 and air at ambient pressure. The overall dimension is of the order of cm. Nine combustion simulations have been carried out assuming detailed chemistry, several length/diameter ratios (Z/D = 3, 5 and 11) and equivalence ratios (0.4, 0.7 and 1);all are at 400 W of injected chemical power. Among the most important results are the converter surfaces temperatures, the heat loads, provided to the environment, and the chemical efficiency. The high chemical efficiency, > 99.9%, is due to the relatively long average gas residence time coupled with the fairly good mixing due to the swirl motion and the impinging air/fuel jets that provide heat and radicals to the flame.
The fluid-structure interaction (FSI) effect should be carefully considered in a seismic analysis of nuclear reactor internals to obtain the appropriate seismic responses because the dynamic characteristics of reactor...
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The fluid-structure interaction (FSI) effect should be carefully considered in a seismic analysis of nuclear reactor internals to obtain the appropriate seismic responses because the dynamic characteristics of reactor internals change when they are submerged in the reactor coolant. This study suggests that a seismic analysis methodology considered the FSI effect in an integral reactor, and applies the methodology to the System-Integrated Modular Advanced Reactor (SMART) developed in Korea. In this methodology, we especially focus on constructing a numerical analysis model that can represent the dynamic behaviors considered in the FSI effect. The effect is included in the simplified seismic analysis model by adopting the fluid elements at the gap between the structures. The overall procedures of the seismic analysis model construction are verified by using dynamic characteristics extracted from a scaled-down model, and then the time history analysis is carried out using the constructed seismic analysis model, applying the El Centro earthquake input in order to obtain the major seismic responses. The results show that the seismic analysis model can clearly provide the seismic responses of the reactor internals. Moreover, the results emphasize the importance of the consideration of the FSI effect in the seismic analysis of the integral reactor.
In this paper, the applicability of the homotopy perturbation method (HPM) in analyzing the flutter of geometrically nonlinear cross-ply rectangular laminated plates resting on nonlinear elastic foundation is investig...
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In this paper, the applicability of the homotopy perturbation method (HPM) in analyzing the flutter of geometrically nonlinear cross-ply rectangular laminated plates resting on nonlinear elastic foundation is investigated. The piston theory is employed to evaluate the aerodynamic pressure acting on the plate. The von Karman geometric nonlinear theory is used to construct the governing equations of the system. The Galerkin's method is used to reduce the nonlinear partial differential equations to a nonlinear second-order ordinary differential equation, and the HPM is employed to study the effect of initial deflection, aspect ratio and stacking sequence on the flutter pressure of cross-ply laminated plates. The results show that the first approximation of the HPM leads to highly accurate solutions for the geometrically nonlinear flutter of cross-ply rectangular laminated plates subjected to the aerodynamic pressure.
A partitioned implicit coupling strategy is proposed for fluid-structure interaction (FSI) problems in this paper. The incompressible Navier-Stokes equations under arbitrary Lagrangian-Eulerian description are solved ...
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A partitioned implicit coupling strategy is proposed for fluid-structure interaction (FSI) problems in this paper. The incompressible Navier-Stokes equations under arbitrary Lagrangian-Eulerian description are solved by the characteristic-based split scheme while the structural equation is evaluated by the composite implicit time integration method. Moving submesh approach is performed for the mesh deformation and a mass source term (MST) is introduced into the pressure Poisson equation for respecting geometric conservation law. fluid-structure coupling is achieved by the combined interface boundary condition (CIBC) method. The iterative loops are realized by fixed-point iterations with Aitken's Delta(2) method. A structural force predictor is employed within the present algorithm, ensuring that the latest quantities belonging to different subdomains are adopted for the CIBC method. The proposed methodology is validated by flow-induced oscillations of a bluff body. The obtained results agree with the well-documented data. Some well-known flow phenomena have been detected successfully.
A semi-implicit coupling strategy under the arbitrary Lagrangian-Eulerian description is presented for the incompressible fluid flow past a geometrically nonlinear solid in this paper. The incompressible fluid is solv...
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A semi-implicit coupling strategy under the arbitrary Lagrangian-Eulerian description is presented for the incompressible fluid flow past a geometrically nonlinear solid in this paper. The incompressible fluid is solved by means of the characteristic-based split (CBS) finite element method while the cell-based smoothed finite element method is employed to settle the governing equation of the geometrically nonlinear solid. Because of the CBS fluid solver, the present coupling strategy is performed in a semi-implicit fashion. In particular, the first step of the CBS scheme is explicitly treated whereas the others are implicitly coupled with the structural motion. The computational cost is hence reduced because no subiterations are included in the explicit coupling step and the fluid mesh is frozen in the implicit coupling step. A classic cantilever problem is dealt with to validate the structural solver, and then flow-induced vibrations of a restrictor flap in a uniform channel flow is analyzed in detail. The obtained results agree well with the existing data.
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