The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Hilmi Demiray - One of the best experts on this subject based on the ideXlab platform.
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weakly non linear waves in a tapered elastic tube filled with an Inviscid Fluid
International Journal of Non-linear Mechanics, 2005Co-Authors: Ilkay Bakirtas, Hilmi DemirayAbstract:In the present work, treating the artery as a tapered, thin walled, long and circularly conical prestressed elastic tube and using the longwave approximation, we have studied the propagation of weakly non-linear waves in such a Fluid-filled elastic tube by employing the reductive perturbation method. By considering the blood as an incompressible Inviscid Fluid, the evolution equation is obtained as the Korteweg-de Vries equation with a variable coefficient. It is shown that this type of equation admits a solitary wave-type solution with variable wave speed. It is observed that, the wave speed decreases with distance for positive tapering while it increases for negative tapering. It is further observed that, the progressive wave profile for expanding tubes (a>0) becomes more steepened whereas for narrowing tubes (a<0) it becomes more flattened.
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nonlinear waves in a thick walled viscoelastic tube filled with an Inviscid Fluid
International Journal of Engineering Science, 1998Co-Authors: Hilmi DemirayAbstract:Abstract In the present work, we studied the propagation of small but finite amplitude waves in a prestressed thick-walled viscoelastic tube filled with an incompressible Inviscid Fluid. In order to include the dispersion, the wall's inertial and shear effects are taken into account in determining the inner pressure–inner cross-sectional area relation. Using the reductive perturbation method, the propagation of weakly nonlinear waves in the long-wave approximation is investigated. After obtaining the general evolution equation in the long-wave approximation, by a proper scaling, it is shown that this general equation reduces to the well-known evolution equations such as the Burgers, Korteweg–deVries and Korteweg–deVries–Burgers equations. The variations of solution profile with initial deformation, thickness ratio and the viscosity coefficients are numerically evaluated and the results are illustrated in some figures.
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nonlinear waves in an Inviscid Fluid contained in a prestressed viscoelastic thin tube
Zeitschrift für Angewandte Mathematik und Physik, 1997Co-Authors: Hilmi Demiray, Nalan AntarAbstract:In the present work, we examine the propagation of weakly nonlinear waves in a prestressed thin viscoelastic tube filled with an incompressible Inviscid Fluid. Considering that the arteries are initially subjected to a large static transmural pressure P0 and an axial stretch \(\lambda_z\) and, in the course of blood flow, a finite time dependent displacement is added to this initial field, the nonlinear equation governing the motion in the radial direction is obtained. Using the reductive perturbation technique, the propagation of weakly nonlinear waves in the long-wave approximation is studied. After obtaining the general equation in the long-wave approximation, by a proper scaling, it is shown that this general equation reduces to the well-know nonlinear evolution equations. Intensifying the effect of nonlinearity in the perturbation process, the modified forms of these evolution equations are also obtained.
Konstantin Ilin - One of the best experts on this subject based on the ideXlab platform.
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on the stability of the dynamical system rigid body Inviscid Fluid
Journal of Fluid Mechanics, 1999Co-Authors: V A Vladimirov, Konstantin IlinAbstract:We study a dynamical system consisting of a rigid body and an Inviscid incompressible Fluid. Two general configuraions of the system are considered: (a) a rigid body with a cavity completely filled with a Fluid and (b) a rigid body surrounded by a Fluid. In the first case the Fluid is confined to an interior (for the body) domain and in the second case it occupies an exterior domain, which may, in turn, be bounded by some fixed rigid boundary or may extend to infinity. The aim of the paper is twofold: (i) to develop Arnold's technique for the system 'body + Fluid' and (ii) to obtain sufficient conditions for the stability of steady states of the system. We first establish an energy-type variational principle for an arbitrary steady state of the system. Then we generalize this principle for states that are steady either in translationally moving in some fixed direction or rotating around some fixed axis coordinate system. The second variations of the corresponding functionals are calculated. The general results are applied to a number of particular stability problems. The first is the stability of a steady translational motion of a two-dimensional body in an irrotational flow
Shi-qiang Dai - One of the best experts on this subject based on the ideXlab platform.
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Flexural-Gravity Waves Due to Transient Disturbances in an Inviscid Fluid of Finite Depth
Journal of Hydrodynamics, 2008Co-Authors: Shi-qiang DaiAbstract:The dynamic response of an ice-covered Fluid to transient disturbances was analytically investigated by means of integral transforms and the generalized method of stationary phase. The initially quiescent Fluid of finite depth was assumed to be Inviscid, incompressible, and homogenous. The thin ice-cover was modeled as a homogeneous elastic plate. The disturbances were idealized as the fundamental singularities. A linearized initial-boundary-value problem was formulated within the framework of potential flow. The perturbed flow was decomposed into the regular and the singular components. An image system was introduced for the singular part to meet the boundary condition at the flat bottom. The solutions in integral form for the vertical deflexion at the ice-water interface were obtained by means of a joint Laplace-Fourier transform. The asymptotic representations of the wave motion were explicitly derived for large time with a fixed distance-to-time ratio. The effects of the finite depth of Fluid on the resultant wave patterns were discussed in detail. As the depth increases from zero, the critical wave number and the minimal group velocity first increase to their peak values and then decrease to constants.
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Flexural- and capillary-gravity waves due to fundamental singularities in an Inviscid Fluid of finite depth
International Journal of Engineering Science, 2008Co-Authors: Shi-qiang DaiAbstract:Wave motion due to line, point and ring sources submerged in an Inviscid Fluid are analytically investigated. The initially quiescent Fluid of finite depth, covered by a thin elastic plate or by an inertial surface with the capillary effect, is assumed to be incompressible and homogenous. The strengths of the sources are time-dependent. The linearized initial-boundary-value problem is formulated within the framework of potential flow. The perturbed flow is decomposed into the regular and the singular components. An image system is introduced for the singular part to meet the boundary condition at the flat bottom. The solutions in integral form for the velocity potentials and the surface deflexions due to various singularities are obtained by means of a joint Laplace–Fourier transform. To analyze the dynamic characteristics of the flexural- and capillary-gravity waves due to unsteady disturbances, the asymptotic representations of the wave motion are explicitly derived for large time with a fixed distance-to-time ratio by virtue of the Stokes and Scorer methods of stationary phase. It is found that the generated waves consist of three wave systems, namely the steady-state gravity waves, the transient gravity waves and the transient flexural/capillary waves. The transient wave system observed depends on the moving speed of the observer in relation to the minimal and maximal group velocities. There exists a minimal depth of Fluid for the possibility of the propagation of capillary-gravity waves on an inertial surface. Furthermore, the results for the pure gravity and capillary-gravity waves in a clean surface can also be recovered as the flexural and inertial parameters tend to zero.
Pius Kirrmann - One of the best experts on this subject based on the ideXlab platform.
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Capillary Gravity Waves on the Free Surface of an Inviscid Fluid of Infinite Depth. Existence of Solitary Waves
Archive for Rational Mechanics and Analysis, 1996Co-Authors: Gérard Iooss, Pius KirrmannAbstract:Permanent capillary gravity waves on the free surface of a two dimensional Inviscid Fluid of infinite depth are investigated. An application of the hodograph transform converts the free boundary-value problem into a boundary-value problem for the Cauchy-Riemann equations in the lower halfplane with nonlinear differential boundary conditions. This can be converted to an integro-differential equation with symbol-k^2 + 4|k|-4(1 +µ), where µ is a bifurcation parameter. A normal-form analysis is presented which shows that the boundary-value problem can be reduced to an integrable system of ordinary diflerential equations plus a remainder term containing nonlocal terms of higher order for |µ| small. This normal form system has been studied thoroughly by several authors (Iooss & Kirchgaessner [8], Iooss & Pérouème [10], Dias & Iooss [5]). It admits a pair of solitary-wave solutions which are reversible in the sense of Kirchgaessner [11]. By applying a method introduced in [11], it is shown that this pair of reversible solitary waves persists for the boundary-value problem, and that the decay at infinity of these solitary waves is at least like 1/[x].
Darren Crowdy - One of the best experts on this subject based on the ideXlab platform.
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Fluid structure interaction of two bodies in an Inviscid Fluid
Physics of Fluids, 2010Co-Authors: Andrew A Tchieu, Darren Crowdy, Anthony LeonardAbstract:The interaction of two arbitrary bodies immersed in a two-dimensional Inviscid Fluid is investigated. Given the linear and angular velocities of the bodies, the solution of the potential flow problem with zero circulation around both bodies is reduced to the determination of a suitable Laurent series in a conformally mapped domain that satisfies the boundary conditions. The potential flow solution is then used to determine the force and moment acting on each body by using generalized Blasius formulas. The current formulation is applied to two examples. First, the case of two rigid circular cylinders interacting in an unbounded domain is investigated. The forces on two cylinders with prescribed motion (forced-forced) is determined and compared to previous results for validation purposes. We then study the response of a single “free” cylinder due to the prescribed motion of the other cylinder (forced-free). This forced-free situation is used to justify the hydrodynamic benefits of drafting in aquatic locomotion. In the case of two neutrally buoyant circular cylinders, the aft cylinder is capable of attaining a substantial propulsive force that is the same order of magnitude of its inertial forces. Additionally, the coupled interaction of two cylinders given an arbitrary initial condition (free-free) is studied to show the differences of perfect collisions with and without the presence of an Inviscid Fluid. For a certain range of collision parameters, the Fluid acts to deflect the cylinder paths just enough before the collision to drastically affect the long time trajectories of the bodies. In the second example, the flapping of two plates is explored. It is seen that the interactions between each plate can cause a net force and torque at certain instants in time, but for idealized sinusoidal motions in irrotational potential flow, there is no net force and torque acting at the system center.
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the irrotational motion generated by two planar stirrers in Inviscid Fluid
Physics of Fluids, 2007Co-Authors: Darren Crowdy, Amit Surana, K Y YickAbstract:The irrotational motion of an Inviscid incompressible Fluid driven by two objects, of arbitrary shape, moving at specified velocities in a two-dimensional Fluid region is determined. The problem is shown to be equivalent to a standard mathematical problem in potential theory known as the modified Schwarz problem. The solution is given, up to conformal mapping, by the classical Villat formula.
