Showing papers on "Added mass published in 2005"
TL;DR: A simplified model representing the interaction between a potential fluid and a linear elastic thin tube is considered, which reproduces propagation phenomena and takes into account the added-mass effect of the fluid on the structure, which is known to be source of numerical difficulties.
875 citations
TL;DR: It is found that in a particular limit corresponding to a low-density fluid flowing over a soft high-density flag, the flapping instability is akin to a resonance between the mode of oscillation of a rigid pivoted airfoil in a flow and a hinged-free elastic plate vibrating in its lowest mode.
Abstract: We give an explanation for the onset of fluid-flow-induced flutter in a flag. Our theory accounts for the various physical mechanisms at work: the finite length and the small but finite bending stiffness of the flag, the unsteadiness of the flow, the added mass effect, and vortex shedding from the trailing edge. Our analysis allows us to predict a critical speed for the onset of flapping as well as the frequency of flapping. We find that in a particular limit corresponding to a low-density fluid flowing over a soft high-density flag, the flapping instability is akin to a resonance between the mode of oscillation of a rigid pivoted airfoil in a flow and a hinged-free elastic plate vibrating in its lowest mode.
280 citations
TL;DR: This work addresses two difficult points in the simulation of blood flows in compliant vessels: the fluid and structure meshes generation and the solution of the fluid-structure problem with large displacements.
201 citations
TL;DR: This article presents a unified state-space model for ship maneuvering, station-keeping, and control in a seaway by separating the vessel model into a low-frequency model and a wave- frequencies model, which is commonly used for simulation.
Abstract: This article presents a unified state-space model for ship maneuvering, station-keeping, and control in a seaway. The frequency-dependent potential and viscous damping terms, which in classic theory results in a convolution integral not suited for real-time simulation, is compactly represented by using a state-space formulation. The separation of the vessel model into a low-frequency model (represented by zero-frequency added mass and damping) and a wave-frequency model (represented by motion transfer functions or RAOs), which is commonly used for simulation, is hence made superfluous.
164 citations
TL;DR: In this paper, a 2D Navier-Stokes equation was used to analyze the 2D sloshing motion of a tank and the boundary of the tank was mapped onto a fixed square domain through proper mapping functions and stretched meshes were employed near boundaries to more accurately evaluate the large disturbance of fluid along the boundary.
126 citations
TL;DR: In this paper, a model based on a slender-body approximation and unsteady potential flow theory was proposed for a ribbon hanging in a vertical air stream, which showed that the critical flow velocity depends strongly on the length of the ribbon.
88 citations
TL;DR: In this article, the authors investigated the limits imposed by thermomechanical noise on both the linear operating regime of a simple harmonic oscillator and the equivalent limits on nonlinear parametric amplifiers used as parametric sensors.
Abstract: Measuring and monitoring the dynamic parameters of a nanomechanical resonator, in particular the resonance frequency, has received significant attention recently, in part due to the possibility of very sensitive, fast and precise mass sensing. Added mass can include chemisorbed or physisorbed metalsororganicmolecules,andifsufficientlyhighsensitivity,dynamicrangeand detector speed can be achieved, they could have applications in, e.g., proteomics. Here, I investigate some of the fundamental limits to mass sensing in such resonators, discussing the limits imposed by thermomechanical noise on both the linear operating regime of a simple harmonic oscillator, and the equivalent limits on nonlinear parametric amplifiers used as parametric sensors. The model system is a cantilevered flexural resonator, but the results apply equally well (in most cases) to doubly clamped or torsional resonant structures as well.
88 citations
TL;DR: In this article, the authors describe the characteristics of fluid forces and wake patterns of a circular cylinder oscillating in the streamwise direction in a cross-flow, on the basis of precise measurements and flow-visualizations in forced-oscillation tests in a water tunnel at subcritical Reynolds numbers.
68 citations
TL;DR: In this article, a new monolithic approach based on the fluid pressure Poisson equation (PPE) was proposed to solve an interaction problem of incompressible viscous fluid and an elastic body.
Abstract: This paper describes a new monolithic approach based on the fluid pressure Poisson equation (PPE) to solve an interaction problem of incompressible viscous fluid and an elastic body. The PPE is derived so as to be consistent with the coupled equation system for the fluid-structure interaction (FSI). Based on this approach, we develop two kinds of efficient monolithic methods. In both methods, the fluid pressure is derived implicitly so as to satisfy the incompressibility constraint, and all other unknown variables are derived fully explicitly or partially explicitly. The coefficient matrix of the PPE for the FSI becomes symmetric and positive definite and its condition is insensitive to inhomogeneity of material properties. The arbitrary Lagrangian–Eulerian (ALE) method is employed for the fluid part in order to take into account the deformable fluid-structure interface. To demonstrate fundamental performances of the proposed approach, the developed two monolithic methods are applied to evaluate the added mass and the added damping of a circular cylinder as well as to simulate the vibration of a rectangular cylinder induced by vortex shedding. Copyright © 2005 John Wiley & Sons, Ltd.
65 citations
TL;DR: In this article, a mixed mode-type magneto-rheological fluid mount (MR mount in short) is devised by considering the nondimensional formulation of Bingham plastic flow, and applied to vibration control of a structural system subjected to external excitations.
Abstract: In this work, a mixed mode-type magneto-rheological fluid mount (MR mount in short) is devised by considering the nondimensional formulation of Bingham plastic flow, and applied to vibration control of a structural system subjected to external excitations. The structural system consists of a vibrating mass, semi-active MR fluid mount, and passive rubber mounts. The MR mount is installed on the beam structure as a semi-active actuator and supports the vibrating mass, while the flexible beam structure is supported by two passive rubber mounts. After verifying the field-dependent damping force characteristics of the MR mount, the governing equation of the structural system is derived in the modal coordinate and rewritten as a state space control model. The linear quadratic Gaussian (LQG) controller is then formulated in order to attenuate vibration of the structural system. The LQG controller is experimentally realized and control responses such as accelerations and transmitted forces of the structural system are presented in the frequency domain.
65 citations
Journal Article•
TL;DR: In this paper, a time-domain strip model for simulation of the planing hull in waves is presented. But the model is based on a wave height measurement signal and is not suitable for full-scale measurement data.
Abstract: Simulation of the planing hull in waves has been addressed during the last 25 years and basically been approached by strip methods. This work follows that tradition and describes a time-domain strip model for simulation of the planing hull in waves. The actual fluid mechanical problem is simplified through the strip approach. The load distribution acting on the hull is approximated by determining the section load at a number of hull sections, strips. The section-wise 2-dimensional calculations are expressed in terms of added mass coefficients and used in the formulations of both inertia and excitation forces in the equations of motions. The modeling approach starts from the hypothetic assumption that the transient conditions can be modeled based on those section-wise calculations. The equation of motion is solved in the time-domain. The equation is up-dated at each time step and every iteration step with respect to the momentary distribution of section draught and relative incident velocity between the hull and water and catches the characteristic non-linear behavior of the planing craft in waves. The model follows the principles of the pioneering work of E. E. Zarnick differing on model structure and in details such as the modeling of the lift in the transom area. A major part of the work is concerned with experiments and evaluation of simulations with respect to performed model tests and to published experiment data. Simulations of model tests have been performed and comparisons have been made between measured and simulated time series. The link between simulation and experiment is a wave model which is based on a wave height measurement signal. It is developed and evaluated in the thesis. The conclusions are in favor of the 2-dimensional approach to modeling the conditions for the planing hull in waves and among further studies is evaluation of simulated loads and motions to full-scale trial measurement data.
TL;DR: In this article, a generalized added mass approach was proposed to model the acoustic gas-solid interaction Reynolds stress term, which corresponds to a redistribution of the filtered gas phase pressure gradient over the phases.
Abstract: To account for mesoscale phenomena in coarse grid simulations, Reynolds stress terms appearing in the filtered gas-solid flow equations have to be modeled. A generalized added mass approach previously proposed by Zhang and VanderHeyden [Int. J. Multiphase Flow 28, 805 (2002)] to model the acoustic gas-solid interaction Reynolds stress term is analyzed. Theoretically, it is shown that a generalized added mass term appears directly from the filtered acoustic gas-solid interaction term and that it corresponds to a redistribution of the filtered gas phase pressure gradient over the phases. This direct contribution scales according to the mean square of the solid volume fraction fluctuations. Two-dimensional dynamic mesoscale simulations over a broad solid volume fraction range and for two domain sizes and two grid resolutions are carried out to calculate the magnitude of the generalized added mass effect. Calculated values of the mean square of the solid volume fraction fluctuations are qualitatively in agreement with the experimental observations of Zenit and Hunt [Int. J. Multiphase Flow 26, 763 (2000)]. A second, indirect contribution to the generalized added mass term from the filtered acoustic gas-solid interaction term is shown to be statistically significant, but one order of magnitude smaller than the direct contribution. A further quantification of the maximum generalized added mass effect as a function of the filter frequency is obtained from a mixture speed of sound test. The results show that a large generalized added mass coefficient, as previously reported by Zhang and VanderHeyden [Int. J. Multiphase Flow 28, 805 (2002)], is justified only in case the filter frequency is low (< 20 Hz), i.e., if the grid is, either spatially or temporally, sufficiently coarse. (c) 2005 American Institute of Physics.
TL;DR: In this paper, a hybrid method is developed for predicting the highfrequency vibration response of fluid-loaded cylindrical shells with periodic circumferential stiffeners, which includes added mass and radiation effects due to the surrounding exterior fluid medium.
TL;DR: In this paper, two highly efficient fully-coupled methods of predicting the resonant forced response of turbomachinery blades have been developed with the intention of increased computational efficiency over a decoupled method.
TL;DR: In this article, the coupled flexural-torsional free and forced vibrations of a beam with tip and/or in-span attachments are studied, and the modal functions of this model and the orthogonality condition among them are derived.
TL;DR: In this paper, an energy finite element analysis (EFEA) formulation for high frequency vibration analysis of stiffened plates under heavy fluid loading is presented, and the added mass effect and the radiation damping effect due to the fluid loading are incorporated in the derivation of the EFEA governing differential equations.
TL;DR: In this paper, a two-dimensional laminar channel flow divided by a plate and another two dimensional Laminar flow caused by the oscillation of a vertical plate in a cavity filled with a fluid are considered to investigate the dynamic FSI between the fluid and the plate.
TL;DR: In this article, a simple approach is proposed that can be used to readily determine the eigenvalues of an arbitrarily supported single-span or multi-span beam carrying any combination of lumped mass.
TL;DR: In this paper, an approach combining finite element with boundary element methods is proposed to calculate the elastic vibration and acoustic field radiated from an underwater structure, where the FEM software NASTRAN is employed for computation of the structural vibration.
TL;DR: In this article, a criterion for the transition from the homogeneous to the heterogeneous regime in a bubble column is developed based on the theory of linear stability, and a good agreement has been obtained between the experimental transition gas hold-up and the predictions of the same obtained by the theory developed in this work.
TL;DR: In this article, the displacement functions for the immersed part and emerged part of a doubly tapered beam are derived and the force (and moment) equilibrium conditions and the deflection compatibility conditions for the two parts are imposed to establish a set of simultaneous equations with eight integration constants as the unknowns.
TL;DR: In this paper, the authors describe the experiments on shallow-water flat-bottom slamming of a circular disk and evaluate the dependence of the added mass of a disk on water depth and impact velocity.
TL;DR: In this paper, free undamped in-plane vibrations of shear unbounded curved beams around their highly buckled configurations are investigated neglecting rotary inertia effects, and the solutions of the associated eigenvalue problems are found employing two approaches: a semi-analytical method based on Galerkin discretization and a finite element method.
Abstract: Free undamped in-plane vibrations of shear undeformable beams around their highly buckled configurations are investigated neglecting rotary inertia effects. The beams are inertially nonuniform since a lumped mass is rigidly clamped along the span. Two mechanical models are considered depending on the boundary conditions in the post-buckling phases. First, the beam is considered inextensible because it is hinged at one end and is acted upon by an axial compressive force on the other end, a roller support, both in the buckling and post-buckling phases. In the second model, the beam is extensible in the post-buckling phase because the roller support boundary is changed into a fixed hinged end. Free undamped vibrations are governed, in the first case, by a homogeneous integral-partial-differential equation and, in the second case, by two coupled partial-differential equations with variable coefficients. The solutions of the associated eigenvalue problems are found employing two approaches: a semi-analytical method based on Galerkin discretization and a finite element method. A close agreement in the outcomes is found. The leading differences relating to the natural frequencies and linear normal modes of the two pre-stressed curved beam models are discussed; in particular, the occurrence of the veering phenomenon and the crossovers are outlined.
TL;DR: A fixed-mesh method for general moving objects in fluid flow was developed and implemented into the commercial CFD software FLOW-3D and a good agreement is achieved between computational and experimental results in an application to a valve problem.
Abstract: In this work, a fixed-mesh method for general moving objects in fluid flow was developed and implemented into the commercial CFD software FLOW-3D. A general moving object is a rigid body with any type of six-degrees-of-freedom, fixed-point and fixed-axis motion which can be either user-prescribed or dynamically coupled with fluid flow. The method allows multiple general moving objects, and each of them can possess any different type of motion. Area and volume fractions to represent the objects in the fixed-grid are calculated at every time step to describe time-variation of object locations and orientations. Continuity and momentum equations for fluid are modified to account for the effects of object motion on fluid flow. A good agreement is achieved between computational and experimental results in an application to a valve problem.
TL;DR: In this paper, the authors deal with the simulation of fluid structure interaction problems in large deformation, and discuss two aspects of their numerical solution: (i) the derivation of energy conserving time integration schemes in presence of fluid structures coupling, moving grids, and nonlinear kinematic constraints such as incompressibility and contact, and (ii) the introduction of adequate preconditioners efficiently chaining local fluid and structure solvers.
01 Jan 2005
TL;DR: In this paper, the entrapment of inclusions, bubbles, slag, and other particles into solidified steel products is simulated using a Lagrangian approach to track the trajectories.
Abstract: The entrapment of inclusions, bubbles, slag, and other particles into solidified steel products is a critically-important quality concern. During continuous casting, particles may enter the mold with the steel flowing through the submerged nozzle. In addition, mold slag may be entrained from the top surface. A computational model has been developed to simulate the transport and entrapment of particles from both of these sources. The model first computes transient turbulent flow in the mold region using Large Eddy Simulation (LES), with the sub-grid-scale (SGS) k model. Next, the transport and capture of over 30,000 particles are simulated using a Lagrangian approach to track the trajectories. A new criterion was developed to model particle pushing and capture by a dendritic interface and was incorporated into the particle transport model. Particles smaller than the primary dendrite arm spacing are entrapped if they enter the boundary layer region and touch the solidifying steel shell. Larger particles are entrapped only if they remain stable while the shell grows around them. The new criterion models this by considering a balance of ten different forces which act on a particle in the boundary layer region, including the bulk hydrodynamic forces (lift, pressure gradient, stress gradient, Basset, and added mass forces), transverse drag force, (caused by fluid flow across the dendrite interface), gravity (buoyancy) force, and the forces acting at the interface (Van der Waals interfacial force, lubrication drag force, and surface energy gradient force). The criterion was validated by reproducing experimental results in two different systems. Finally, the model was used to predict the entrapment distributions, removal rates, and fractions of different sized particles in a straight-walled thin slab caster. Although more large particles are safely removed than small ones, the capture rate as defects is still very high.
01 Jan 2005
TL;DR: In this article, the effects of oscillation amplitude and opening size on the hydrodynamic forces acting on the plates whilst undergoing forced heave motion were investigated, and the coefficient values obtained were compared with the published data available.
Abstract: For truss SPAR platforms, damping plates are employed to increase the added mass and viscous drag in the heave direction. The paper aims to investigate experimentally the hydrodynamic forces on heave plates with different opening sizes. Model scale experiments were carried out on three 40 by 40cm flat plates to investigate the effects of oscillation amplitude and opening size on the hydrodynamic forces acting on the plates whilst undergoing forced heave motion. Three different methods of data processing were investigated, namely, directly processing unfiltered data to obtain the hydrodynamic coefficients, filtering the data before evaluating the coefficients and fitting the filtered data to a sine curve before evaluating the coefficients. The most accurate method was then selected and used to evaluate the experiment results. The coefficient values obtained were compared with the published data available. The effects of various variables such as opening size, KC number, frequency of oscillation on the hydrodynamic coefficients were also studied. Relative magnitudes of the drag and inertia components of the overall hydrodynamic load are compared.Copyright © 2005 by ASME
TL;DR: In this paper, four kinds of moving mass elements, 1st-node, 2nd-node and full and short-range mass elements are presented, where the full mass element refers to that with mass distributed from the first node (or second node) to the arbitrary position of a two-node beam element, while the short range mass element is the case with its location arbitrary on a beam element.
Abstract: Four kinds of moving mass elements, 1st-node, 2nd-node, full and short-range mass elements, are presented, where the 1st-node (or 2nd-node) mass element refers to that with mass distributed from the first node (or second node) to the arbitrary position of a two-node beam element, the full mass element is the special case of the 1st-node (or 2nd-node) mass element with mass distributed over the full length of the beam element, while the short-range mass element is the case with its location arbitrary on a beam element. If the total range of a distributed mass is denoted by R and the length of each beam element is denoted by , then, for the case of R≥, one may model the distributed mass on the beam using the combination of the 1st-node, 2nd-node and full mass elements, while for the case of R <, one may model the distributed mass using the short-range mass element. It has been found that the effects of the vertical (y) and horizontal (x) inertia forces, Coriolis force and centrifugal force induced by the moving distributed mass can be easily taken into the formulations by means of the last concept. To illustrate the application of the presented theory, the dynamic analysis of a pinned-pinned beam and that of a portal frame under the action of a moving uniformly distributed mass are performed by means of the finite element method and the Newmark integration method. Numerical results show that some pertinent factors, such as Coriolis force, centrifugal force, acceleration, velocity and total range of the moving distributed mass, have significant influences on the vertical (y) and horizontal (x) response of a structure.
TL;DR: In this article, the authors investigate the influence of pre-stress state on the natural periods and mode shapes of steel cylindrical tanks and on the response under horizontal motions, and show that the pre-stress state has a significant influence in the natural period and mode shape of tank-liquid systems with thinner walls.
Abstract: In this paper we investigate the influence of hydrostatic pressure and self-weight loads (pre-stress state) on the natural periods and mode shapes of steel cylindrical tanks and on the response under horizontal motions. The tank structure is modeled with finite elements and added mass models are used to represent the liquid. Only the impulsive component of the hydrodynamic response is considered. The natural periods and mode shapes for tank-liquid systems including and neglecting the effect of the pre-stress state are computed and compared. Three tank-liquid systems with different cylinder height to diameter ratios and slenderness ratios are considered. The numerical results show that the pre-stress state has a significant influence in the natural periods and mode shapes of tank-liquid systems with thinner walls; however, for thicker shells this effect is reduced. When the pre-stress state is neglected and included, the smaller differences in natural periods occur, for modes characterized by small circumf...