• Coupled systems mechanics
• /
• 제6권3호
• /
• pp.287-316
• /
• 2017

This paper studies the particularities of the forced vibration of the hydro-elastic system consisting of a moving elastic plate, compressible viscous fluid and rigid wall. This study is made by employing the discrete-analytical solution method proposed in the paper by the authors (Akbarov and Panakhli (2015)). It is assumed that in the initial state the fluid flow is caused by the axial movement of the plate and the additional lineally-located time-harmonic forces act on the plate and these forces cause additional flow field in the fluid and a stress-strain state in the plate. The stress-strain state in the plate is described by utilizing the exact equations and relations of the linear elastodynamics. However, the additional fluid flow field is described with linearized Navier-Stokes equations for a compressible viscous fluid. Numerical results related to the influence of the problem parameters on the frequency response of the normal stress acting on the plate fluid interface plane and fluid flow velocity on this plane are presented and discussed. In this discussion, attention is focused on the influence of the initial plate axial moving velocity on these responses. At the same, it is established that as a result of the plate moving a resonance type of phenomenon can take place under forced vibration of the system. Moreover, numerical results regarding the influence of the fluid compressibility on these responses are also presented and discussed.

• Structural Engineering and Mechanics
• /
• 제50권1호
• /
• pp.53-71
• /
• 2014

A semi-analytical method is developed to consider free vibrations of a functionally graded elastic plate resting on Winkler elastic foundation and in contact with a quiescent fluid. Material properties are assumed to be graded distribution along the thickness direction according to a power-law in terms of the volume fractions of the constituents. The fluid is considered to be incompressible and inviscid. In the analysis, the effect of an in-plane force in the plate due to the weight of the fluid is taken into account. By satisfying the compatibility conditions along the interface of fluid and plate, the fluid-structure interaction is taken into account and natural frequencies and mode shapes of the coupled system are acquired by employing energy methods. The results obtained from the present approach are verified by those from a finite element analysis. Besides, the effects of volume fractions of functionally graded materials, Winkler foundation stiffness and in-plane forces on the dynamic of plate are elucidated.

• 대한기계학회논문집
• /
• 제15권6호
• /
• pp.1799-1806
• /
• 1991

본 연구에서는 양단이 지지된 단순 모델을 사용하여, 양단 사이의 한 위치에 탄성지지를 할 때 고유진동수 변화를 검토하고 고유진동수를 높이는 방안을 제시하고 자 한다. 또한 분산변수계(distributed parameter system)을 사용하는 경우, 일반적 으로 홀수차항이 있는 미분방정식에서 그 해를 다항식, 고유벡터나 삼각함수의 무한개 의 합 등으로 표시하고 있으나 본 연구에서는 미분 방정식으로 표시하는 방법을 사용 하여 완전해(closed form solution)로 표시하여 구함으로서 오차를 제거하고 계산을 간결하게 하였다.

• Journal of Mechanical Science and Technology
• /
• 제19권9호
• /
• pp.1761-1772
• /
• 2005

In blood flow passing through the mechanical heart valve (MHV) and elastic blood vessel, hemolysis and platelet activation causing thrombus formation can be seen owing to the shear stress in the blood. Also, fracture and deformation of leaflets can be observed depending on the shape and material properties of the leaflets which is opened and closed in a cycle. Hence, comprehensive study is needed on the hemodynamics which is associated with the motion of leaflet and elastic blood vessel in terms of fluid-structure interaction. In this paper, a numerical analysis has been performed for a three-dimensional pulsatile blood flow associated with the elastic blood vessel and curved bileaflet for multiple cycles in light of fluid-structure interaction. From this analysis fluttering phenomenon and rebound of the leaflet have been observed and recirculation and regurgitation have been found in the flow fields of the blood. Also, the pressure distribution and the radial displacement of the elastic blood vessel have been obtained. The motion of the leaflet and flow fields of the blood have shown similar tendency compared with the previous experiments carried out in other studies. The present study can contribute to the design methodology for the curved bileaflet mechanical heart valve. Furthermore, the proposed fluid-structure interaction method will be effectively used in various fields where the interaction between fluid flow and structure are involved.

• Structural Engineering and Mechanics
• /
• 제59권3호
• /
• pp.403-430
• /
• 2016

This paper studies the dynamics of the lineal-located time-harmonic moving-with-constant-velocity load which acts on the hydro-elastic system consisting of the elastic plate, compressible viscous fluid - strip and rigid wall. The plane-strain state in the plate is considered and its motion is described by employing the exact equations of elastodynamics but the plane-parallel flow of the fluid is described by the linearized Navier-Stokes equations. It is assumed that the velocity and force vectors of the constituents are continuous on the contact plane between the plate and fluid, and impermeability conditions on the rigid wall are satisfied. Numerical results on the velocity and stress distributions on the interface plane are presented and discussed and the focus is on the influence of the effect caused by the interaction between oscillation and moving of the external load. During these discussions, the corresponding earlier results by the authors are used which were obtained in the cases where, on the system under consideration, only the oscillating or moving load acts. In particular, it is established that the magnitude of the aforementioned interaction depends significantly on the vibration phase of the system.

• 대한수학회논문집
• /
• 제39권2호
• /
• pp.513-534
• /
• 2024

The main goal of this work is to study an initial boundary value problem relating to the unsteady flow of a rigid, viscoplastic, and incompressible Bingham fluid in an elastic bounded domain of ℝ². By using the approximation sequences of the Faedo-Galerkin method together with the regularization techniques, we obtain the results of the existence and uniqueness of local solutions.

• Structural Engineering and Mechanics
• /
• 제46권6호
• /
• pp.827-842
• /
• 2013

In this paper, the wave propagation in generalized thermo elastic plate immersed in fluid is studied based on the Lord-Shulman (LS) and Green-Lindsay (GL) generalized two dimensional theory of thermo elasticity. Two displacement potential functions are introduced to uncouple the equations of motion. The frequency equations that include the interaction between the plate and fluid are obtained by the perfect-slip boundary conditions using the Bessel function solutions. The numerical calculations are carried out for the material Zinc and the computed non-dimensional frequency, phase velocity and attenuation coefficient are plotted as the dispersion curves for the plate with thermally insulated and isothermal boundaries. The wave characteristics are found to be more stable and realistic in the presence of thermal relaxation times and the fluid interaction.

• Structural Engineering and Mechanics
• /
• 제59권1호
• /
• pp.153-186
• /
• 2016

This paper addresses temperature-dependent nonlinear vibration and instability of embedded functionally graded (FG) pipes conveying viscous fluid-nanoparticle mixture. The surrounding elastic medium is modeled by temperature-dependent orthotropic Pasternak medium. Reddy third-order shear deformation theory (RSDT) of cylindrical shells are developed using the strain-displacement relations of Donnell theory. The well known Navier-Stokes equation is used for obtaining the applied force of fluid to pipe. Based on energy method and Hamilton's principal, the governing equations are derived. Generalized differential quadrature method (GDQM) is applied for obtaining the frequency and critical fluid velocity of system. The effects of different parameters such as mode numbers, nonlinearity, fluid velocity, volume percent of nanoparticle in fluid, gradient index, elastic medium, boundary condition and temperature gradient are discussed. Numerical results indicate that with increasing the stiffness of elastic medium and decreasing volume percent of nanoparticle in fluid, the frequency and critical fluid velocity increase. The presented results indicate that the material in-homogeneity has a significant influence on the vibration and instability behaviors of the FG pipes and should therefore be considered in its optimum design. In addition, fluid velocity leads to divergence and flutter instabilities.

• Coupled systems mechanics
• /
• 제6권4호
• /
• pp.439-464
• /
• 2017

The hydro-elastic system consisting of a pre-stretched highly elastic plate, compressible Newtonian viscous fluid, and the rigid wall is considered and it is assumed that on the plate a lineal-located time-harmonic force acts. It is required to investigate the dynamic behavior of this system and determine how the problem parameters and especially the pre-straining of the plate acts on this behavior. The elasticity relations of the plate are described through the harmonic potential and linearized (with respect to perturbations caused by external time-harmonic force) form of these relations is used in the present investigation. The plane-strain state in the plate is considered and the motion of that is described within the scope of the three-dimensional linearized equations of elastic waves in elastic bodies with initial stresses. The motion of the fluid is described by the linearized Navier-Stokes equations and it is considered the plane-parallel flow of this fluid. The Fourier transform with respect to the space coordinate is applied for a solution to the corresponding boundary-value problem. Numerical results on the frequency response of the interface normal stress and normal velocity and the influence of the initial stretching of the plate on this response are presented and discussed. In particular, it is established that the initial stretching of the plate can decrease significantly the absolute values of the aforementioned quantities.

• 한국음향학회지
• /
• 제38권5호
• /
• pp.511-521
• /
• 2019

본 연구에서는 무한 유체에 놓여있는 유한 길이의 탄성 원통 쉘에 외부에서 비스듬히 평면파가 입사할 때 발생하는 음향 산란 현상을 이론적으로 연구했다. 유한 길이의 원통 쉘에서는 해석적인 산란 해가 존재하지 않기 때문에, Kirchhoff 가정을 적용한 Ye의 산란 기법[Z. Ye, J. Acoust. Soc. Am. 102, 877-884 (1997)]을 사용했다. 탄성 원통 쉘의 특성은 3차원 탄성파 이론을 적용하여 구현했으며 원통 쉘 내부의 유체를 고려했다. 유도된 해석 해를 이용하여 내부 유체가 산란 음장에 미치는 효과, Rayleigh 변수에 대한 산란 음장, 탄성 재질의 변화에 따른 먼 거리 산란 함수를 살펴보았다.