Added mass

About: Added mass is a research topic. Over the lifetime, 2849 publications have been published within this topic receiving 47899 citations.

Time-marching analysis of fluid-coupled systems with large added mass

Abstract: Time-marching stability analysis of fluid-structure interaction problems is considered in this paper. The Navier-Stokes equations and the equation of motion of the structure are integrated simultaneously in time in a coupled manner to assess structural dynamics and thereby the possibility for flutter and/or divergence. A method developed by the authors for the incompressible Navier-Stokes equations consists of combining a Runge-Kutta time integration for the structure with a three-point backward time discretization for the fluid. Problems have been encountered with that method, however, when the fluid-added mass is larger than the structural mass, leading to numerical instability in the integration scheme. A cure to remedy these difficulties is proposed in this paper. It consists of introducing estimates for the added mass, obtained, for example, from potential flow calculations, into the structural equation so as to cancel the fluid inertial forces. To illustrate the possibilities of the method, analysis of the free vibrations of two coaxial cylinders coupled by annular fluid is performed

On bubble forces in turbulent channel flows from direct numerical simulations

Abstract: The prediction of void fraction, which relies on interfacial force models, is a major issue in the context of boiling. The two-fluid model requires the modelling of the momentum transfer between phases. When bubbles are small (particle hypothesis), the momentum transfer is related to interfacial forces acting on bubbles. However, the splitting of these forces into drag, lift, added mass, etc., is not straightforward from the local point of view, where only the total interfacial force is defined as an integral of the constraint over the interface. For large-size bubbles, the particle hypothesis can be questioned. The momentum transfer can then be connected to the forces acting on a fluid element of the vapour phase. Based on the local and averaged formulations of the Navier–Stokes equations, a new balance equation for forces enables us to define lift, drag, added-mass and dispersion forces acting on a fluid element of the vapour phase. This equation gives a local definition for all the forces responsible for spatial distribution of bubbles and reflects the meaning usually assigned to the interfacial forces in the particle approach. Through this means, the link between the local formulation and physical phenomena is established and a new way of modelling the lift force is proposed. Furthermore, a new laminar dispersion force which relies on surface tension and pressure effects is introduced. The analysis of the budget equation on our direct numerical simulation database brings into light the large influence of this laminar dispersion force in the migration process. Different well-known physical behaviours can be modelled via this new force: the horizontal clustering of spherical bubbles in laminar flows and the oscillating trajectories of deformable bubbles.

Nonlocal Timoshenko frequency analysis of single-walled carbon nanotube with attached mass: An alternative hamiltonian approach

Abstract: In the present paper, the nonlocal vibration analysis of single-walled carbon nanotube as nanosized mass-sensor is examined. The nanotube is modeled as a clamped-free Timoshenko beam carrying an attached mass at its free end. Using the nonlocal Timoshenko beam theory, a re-formulation of Hamilton's principle has been presented and the equations of motion and the general corresponding boundary conditions have been derived. The main purpose of this paper is to show the sensitivity of the nanotube to the values of added mass and the in presence of nonlocal parameter on the fundamental frequencies values. Some numerical examples have been performed and discussed and the obtained results are compared with those of available works in literature and listed in bibliography.

Some aspects of load-rate sensitivity in visco-elastic microplane material model

Abstract: The paper describes localization of deformation in a bar under tensile loading. The material of the bar is considered as non- linear viscous elastic and the bar consists of two symmetric halves. It is assumed that the model represents behavior of the quasi-brittle viscous material under uniaxial tension with different loading rates. Besides that, the bar could represent uniaxial stress-strain law on a single plane of a microplane material model. Non-linear material property is taken from the microplane material model and it is coupled with the viscous damper producing non-linear Maxwell material model. Mathematically, the problem is described with a system of two partial differential equations with a nonlinear algebraic constraint. In order to obtain solution, the system of differential algebraic equations is transformed into a system of three partial differential equations. System is subjected to loadings of different rate and it is shown that localization occurs only for high loading rates. Mathematically, in such a case two solutions are possible: one without the localization (unstable) and one with the localization (stable one). Furthermore, mass is added to the bar and in that case the problem is described with a system of four differential equations. It is demonstrated that for high enough loading rates, it is the added mass that dominates the response, in contrast to the viscous and elastic material parameters that dominated in the case without mass. This is demonstrated by several numerical examples.