Showing papers on "Added mass published in 2019"
TL;DR: In this article, the added-mass vorticity was found to be consistent with inviscid unsteady flow theory even in well-developed viscous flows, independent of changes to flow topology due to flow separation.
Abstract: Added mass characterises the additional force required to accelerate a body when immersed in an ideal fluid. It originates from an asymmetric change to the surrounding pressure field so the fluid velocity satisfies the no-through-flow condition. This is intrinsically linked with the production of boundary vorticity. A body in potential flow may be represented by an inviscid vortex sheet and added-mass forces determined using impulse methods. However, most fluids are not inviscid. It has been theorised that viscosity causes the ‘added-mass vorticity’ to form in an intensely concentrated boundary layer region, equivalent to the inviscid distribution. Experimentally this is difficult to confirm due to limited measurement resolution and the presence of additional boundary layer vorticity, some the result of induced velocities from free vorticity in the flow field. The aim of this paper is to propose a methodology to isolate the added-mass vorticity experimentally with particle image velocimetry, and confirm that it agrees with potential flow theory even in separated flows. Experiments on a flat-plate wing undergoing linear and angular acceleration show close agreement between the theoretical and measured added-mass vorticity distributions. This is demonstrated to be independent of changes to flow topology due to flow separation. Flow field impulse and net force are also consistent with theory. This paper provides missing experimental evidence coupling added mass and the production of boundary layer vorticity, as well as confirmation that inviscid unsteady flow theory describes the added-mass effect correctly even in well-developed viscous flows.
46 citations
TL;DR: In this paper, a fully coupled nonlinear simulation tool using Morison's equation is developed to predict the dynamic response of floating offshore wind turbine (FOWT) system under different sea states.
37 citations
TL;DR: In this article, a non-uniform bubble model (NUBM) was applied to predict the external characteristics, phase interaction and internal flow characteristics of a multiphase rotodynamic pump.
36 citations
TL;DR: In this paper, the authors investigate the unsteady hydrodynamic force of solid objects vertically entering water with an air cavity behind the falling body and propose physical models to represent the force components corresponding to the body acceleration, the gravity, and the velocity of the body and the fluid particles.
Abstract: We investigate the unsteady hydrodynamic force of solid objects vertically entering water with an air cavity behind the falling body. Physical models are proposed to represent the force components corresponding to the body acceleration, the gravity, and the velocity of the body and the fluid particles. The theoretical or numerical solutions of the physical models are presented to understand the evolution of the force components. The body-acceleration force component is expressed as the high-frequency added mass times the body acceleration. Near the undisturbed free surface, the added mass grows strongly with increasing the submerged depth. It tends to be steady after the submerged depth is greater than a few characteristic lengths. The gravity force component consists of an upward hydrostatic term and a downward dynamic term. Generally, the hydrostatic term, which is obtained by integrating the gravity term in Bernoulli’s equation over the wetted body surface, is much larger than the gravity force component. For the three-dimensional bodies, the gravity force component is found to vary as a power of the submerged depth, where the exponent is about 0.83. The velocity force component is represented as the drag coefficient defined by the V-squared law, which is characterized by the body geometry. The drag coefficient may experience three successive stages with increasing the submerged depth.
35 citations
TL;DR: In this paper, the authors developed an efficient potential-based numerical model to determine the hydrodynamic added mass for a column with general cross-section under horizontal earthquake and validated the accuracy of the developed model for immersed columns.
35 citations
TL;DR: In this article, the effects of added mass and fluid damping on a flapping membrane are quantified using a simple damped oscillator model, and an analytic model based on thin airfoil theory coupled with a membrane equation is developed to characterize the steady and unsteady aeroelastic behavior of compliant membrane wings under different conditions.
Abstract: We present a theoretical framework to characterize the steady and unsteady aeroelastic behaviour of compliant membrane wings under different conditions. We develop an analytic model based on thin airfoil theory coupled with a membrane equation. Adopting a numerical solution to the model equations, we study the effects of wing compliance, inertia and flapping kinematics on aerodynamic performance. The effects of added mass and fluid damping on a flapping membrane are quantified using a simple damped oscillator model. As the flapping frequency is increased, membranes go through a transition from thrust to drag around the resonant frequency, and this transition is earlier for more compliant membranes. The wake also undergoes a transition from a reverse von Karman wake to a traditional von Karman wake. The wake transition frequency is predicted to be higher than the thrust–drag transition frequency for highly compliant wings.
34 citations
TL;DR: In this paper, a degenerate parametric amplifier (DPA) is embedded into a membrane-in-the-middle cavity driven by a strong control field and a weak probe pulse.
Abstract: We propose and analyze an efficient scheme for realizing high-sensitive mass sensor in a quadratically coupled optomechanical system via nonlinear second-order sideband process. This is achieved by exploiting a well-established optomechanical circumstance, where a degenerate parametric amplifier (DPA) is embedded into a membrane-in-the-middle cavity driven by a strong control field and a weak probe pulse. Beyond the conventional linearized approximation, we derive analytical expressions for the efficiency of a second-order sideband and the sensitivity of a mass sensor by using a perturbation method. In this scheme, an added mass deposited on the dielectric membrane can be measured by monitoring the efficiency variation of second-order sideband generation. Using experimentally achievable parameters, we identify the conditions under which nonlinear gain of DPA allows us to enhance the efficiency of a second-order sideband and improve the sensitivity of a mass sensor beyond what is achievable in the linearly coupled optomechanical system based on the detection of mechanical frequency shift. More importantly, we also find that the maximum efficiency of a second-order sideband and the optimum sensitivity of a mass sensor simultaneously serve as an efficient detection for the added mass of a membrane when a control field and nonlinear gain of DPA become strong. The present proposal offers a practical opportunity to design an all-optical nonlinear mass sensor at the picogram level.
34 citations
TL;DR: In this paper, the authors presented the hydroelastic vibration analysis of clamped rectangular plates, vertically or horizontally submerged in fluid by using isogeometric finite element and boundary element methods.
33 citations
TL;DR: In this article, the mass sensing capability of an array of a few identical electrostatically actuated microbeams is investigated, as a first step toward the implementation of arrays of thousands of such resonant sensors.
Abstract: This paper investigates the mass sensing capability of an array of a few identical electrostatically actuated microbeams, as a first step toward the implementation of arrays of thousands of such resonant sensors. A reduced-order model is considered, and Taylor series are used to simplify the nonlinear electrostatic force. Then, the harmonic balance method associated with the asymptotic numerical method, as well as time integration or averaging methods, is applied to this model, and its results are compared. In this paper, two- and three-beam arrays are studied. The predicted responses exhibit complex branches of solutions with additional loops due to the influence of adjacent beams. Moreover, depending on the applied voltages, the solutions with and without added mass exhibit large differences in amplitude which can be used for detection. For symmetric configurations, the symmetry breaking induced by an added mass is exploited to improve mass sensing.
33 citations
TL;DR: In this paper, an accurate added mass model representation for a flexible elliptical cylinder vibrating in water is presented, where the analytical expressions for the hydrodynamic forces on elliptical cylinders are first derived in the elliptical coordinate system.
31 citations
TL;DR: In this article, the authors proposed added mass and added damping to address the effects of vibration of the damping material on the vibration of a pipe, which can be used to predict the vibration reduction effect in detail, but such analysis requires considerable computation time.
TL;DR: It is demonstrated that a fully partitioned PFEM–FEM coupling based on the IQN-ILS strategy allows the simulation of a very large spectrum of FSI problems without incurring added-mass instabilities.
TL;DR: In this paper, the authors investigated the interaction of water with multiple circular cylinders subjected to earthquake ground motion and incident linear waves respectively, and proposed a finite element model to calculate the earthquake-induced hydrodynamic forces and wave forces on uniform vertical cylinders with arbitrary cross-section.
TL;DR: In this article, the authors investigated the hydrodynamic properties of two tandem flexible cylinders and investigated the influence of the spacing ratio T/D (where T is the center-to-center separation distance between the two cylinders and D is the cylinder diameter).
TL;DR: In this article, the effects of grid scale, time-step, turbulence model, exciting force, and numerical damping on the calculation accuracy of the two-way FSI numerical simulation were analyzed in great detail through comparison with the previously published experimental data.
Abstract: Added mass and hydrodynamic damping play significant roles in fluid-structure interaction (FSI) in hydraulic turbines. Added mass can reduce natural frequencies, while hydrodynamic damping could result in a higher amplitude decay speed of the vibration. In order to quantify the added mass and hydrodynamic damping of a three-dimensional (3D) NACA 0009 hydrofoil with a blunt trailing edge, a two-way FSI simulation method was employed. The effects of grid scale, time-step, turbulence model, exciting force, and numerical damping on the calculation accuracy of the two-way FSI numerical simulation were analyzed in great detail through comparison with the previously published experimental data. Hydraulic force was obtained by using a transitional shear stress transport model at the flow region of the Reynolds number ReL = 0.2 × 106–2 × 106. The vortex shedding frequency, the natural frequency of the first-order bending mode in water, and the hydrodynamic damping ratio obtained from the numerical simulations agree well with the experimental data, with maximum deviations in 6.12%, 4.53%, and 8.82%, respectively. As the flow velocity increases, the natural frequency may not significantly change, while the added mass coefficient gradually increases, considering the effect of added stiffness. Above the first-order bending mode lock-in region, the results indicate that the first-order bending mode hydrodynamic damping ratio increases linearly with velocity. The present numerical achievements offer a higher level of accuracy for predicting the added mass and hydrodynamic damping characteristics of a hydrofoil.
TL;DR: In this article, a new method to determine the roll added mass moment of inertia using CFD simulations based on a harmonic excitation roll motion technique and the results are compared against Bhattacharyya's method.
TL;DR: The robustness and reliability of the 3D flexible multibody aeroelastic framework for an anisotropic flapping wing flight involving battens and membranes with composite material is studied and the accuracy of the coupled solution is validated with the available experimental data.
TL;DR: In this article, the hydrodynamic added mass and the inertial coefficient in Morison equation for earthquake-induced hydrodynamics were examined in a series of dynamic tests and the results showed that the proposed formula and method can be used to estimate the earthquake-induced added mass of cylindrical structures.
TL;DR: In this article, the amplitude-dependent added mass and damping coefficients of perforated plates were investigated using a presently developed Navier-Stokes solver and several comparison and sensitivity studies were presented, in order to validate and verify the solver.
TL;DR: In this article, an acoustic-structural coupling method was used to evaluate the added mass factors of a reduced scale pump-turbine with different axial and radial gap sizes between runner and nearby rigid walls.
Abstract: The gaps between runner and nearby structures play an important role in the dynamic response of runner, especially for pump-turbines. This paper aims to evaluate the gap influence on the added mass and dynamic stress of pump-turbine runner and provide an improved method to predict the resonance of runner.,Acoustic-structural coupling method was used to evaluate the added mass factors of a reduced scale pump-turbine with different axial and radial gap size between runner and nearby rigid walls. Improved one-way fluid-structural interaction (FSI) simulation was used to calculate the dynamic stress of the runner, which takes into account fluid added mass effect. The time-dependent hydraulic forces on the runner surfaces that were obtained from unsteady CFD simulation were transferred to the runner structure as a boundary condition, by using mesh-matching algorithm at the FSI surfaces.,The results show that the added mass factors increase as the gap size decreases. The axial gaps have greater influence on the added mass factors for the in-phase (IP) modes than the counter-phase (CP) and crown-dominant (CD) modes, while the CP and CD modes are very sensitive to the radial gaps. The largest added mass factor is observed in (2 + 4)ND-CP mode (resonance mode). The results reveal that the transient structural dynamic stress analysis, with the consideration of gaps and fluid added mass, can accurately predict the resonance phenomenon. Resonance curve of the pump-turbine has been obtained which agrees well with the test result. The gap fluid has great influence on the resonance condition, while for non-resonance operating points, the effect of gaps on the dynamic stress amplitude is quite small.,This paper provides an accurate method to analyze the dynamic response during runner design stage for safety assessment. The resonance curve prediction has more significance than previous methods which predict the resonance of runner by modal or harmonic analysis.
TL;DR: In this paper, a new methodology to determine hydrodynamic derivatives of a tow-fish underwater vehicle using computational fluid dynamics (CFD) was presented, which consists of added mass, linear damping, and nonlinear damping coefficients.
TL;DR: In this paper, a reduced-order model of an electrically-actuated microcantilever beam with a tip mass deployed as resonant sensor for bio-mass detection and sensing was developed.
Abstract: We apply perturbation techniques to develop a reduced-order model of an electrically-actuated microcantilever beam with a tip mass deployed as resonant sensor for bio-mass detection and sensing. This analytical model is validated against numerical model obtained by combining the differential quadrature method for space discretization and Runge–Kutta for time marching. The model is then employed to analyze the nonlinear dynamics and effectiveness of the bio-mass sensor under varying electric loading and explore novel concepts to quantify the mass of biological entities. The working principle of the present bio-mass sensor is based on inspecting the attenuation in the microbeam vibrations resulting from the biological element being deposited on its tip and then extracting the corresponding mass. The output parameter of the present bio-mass sensor is considered as the change in the maximum beam deflections at the tip with and without added mass. Calibration curves, showing the variations of the output parameter with the added mass, are generated to demonstrate the feasibility of the proposed sensing approach for mass detection of biological elements, particularly the Escherichia coli. Reducing the AC voltage when exciting the microbeam is observed to enhance the sensitivity of the output parameter for specific mass threshold. However, the operational range of the bio-mass sensor can be extended when applying higher DC and AC voltages.
TL;DR: In this article, the authors presented simulations for steady turning of a planing craft by developing a new mathematical model, which is assumed that the craft is free in six-degrees of freedom and all motions are strongly coupled.
TL;DR: The AMP scheme is found to be stable and second-order accurate even for very difficult cases of very light solids, and verified for accuracy and stability for a set of new exact benchmark solutions where finite interface deformations are permitted.
Abstract: An analysis is made of a new partitioned scheme for solving fluid-structure interaction problems involving viscous incompressible flow and compressible elastic-solids. The new scheme is stable, wit...
TL;DR: In this article, the authors extended the realm of pendulum studies to include large amplitude oscillations of heavy and buoyant pendulums in a fluid, and constructed a simple model that takes the buoyancy, added mass, fluid (nonlinear) drag and bearing friction into account.
Abstract: The humble pendulum is often invoked as the archetype of a simple, gravity driven, oscillator. Under ideal circumstances, the oscillation frequency of the pendulum is independent of its mass and swing amplitude. However, in most real-world situations, the dynamics of pendulums is not quite so simple, particularly with additional interactions between the pendulum and a surrounding fluid. Here we extend the realm of pendulum studies to include large amplitude oscillations of heavy and buoyant pendulums in a fluid. We performed experiments with massive and hollow cylindrical pendulums in water, and constructed a simple model that takes the buoyancy, added mass, fluid (nonlinear) drag and bearing friction into account. To first order, the model predicts the oscillation frequencies, peak decelerations and damping rate well. An interesting effect of the nonlinear drag captured well by the model is that, for heavy pendulums, the damping time shows a non-monotonic dependence on pendulum mass, reaching a minimum when the pendulum mass density is nearly twice that of the fluid. Small deviations from the model’s predictions are seen, particularly in the second and subsequent maxima of oscillations. Using time-resolved particle image velocimetry (TR-PIV), we reveal that these deviations likely arise due to the disturbed flow created by the pendulum at earlier times. The mean wake velocity obtained from PIV is used to model an extra drag term due to incoming wake flow. The revised model significantly improves the predictions for the second and subsequent oscillations.
TL;DR: In this article, a method for solving a finite inverse eigenvalue problem arising in the determination of added distributed mass in nanoresonator sensors by measurements of the first N natural frequencies of the free axial vibration under clamped end conditions is presented.
TL;DR: In this article, the authors analyzed the importance of the Basset history force and the added mass force for magnetic particle capture in an axial single wire high gradient magnetic separation filter with a bounded flow field.
TL;DR: In this article, the authors investigated the free vibration of the truncated conical shell with arbitrary boundary conditions, including elastic and inertia force constraints, and derived the equations of motion with elastic boundary constraints by employing Hamilton's principle and the thin-walled shallow shell theory of the Donnell type.
TL;DR: The AMP scheme is found to be stable and second-order accurate, without sub-time-step iterations, even for very difficult cases of very light solids when added-mass and added-damping effects are large.
TL;DR: In this paper, the authors developed analytical solutions to water wave radiation by vertical truncated circular cylinders based on linear potential flow theory, in which the fluid velocity on the interface between different regions is expanded into a set of basis functions involving the Gegenbauer polynomials, and the cube-root singularity of fluid velocity at the side edges of the truncated cylinders is correctly modeled.
Abstract: New analytical solutions to water wave radiation by vertical truncated circular cylinders are developed based on linear potential flow theory. Two typical cylinder configurations of a surface-piercing cylinder and a submerged floating cylinder are considered. The multi-term Galerkin method is employed in the solution procedure, in which the fluid velocity on the interface between different regions is expanded into a set of basis function involving the Gegenbauer polynomials, and the cube-root singularity of fluid velocity at the side edges of the truncated cylinders is correctly modeled. The present solutions have the merits of very rapid convergence. The results with six-figure accuracy for added mass and radiation damping can be obtained using a few truncated numbers in the basis function for three motions (surge, heave and roll). The calculated results of the present solutions agree well with that by a higher-order boundary element method solution. Calculation examples are presented to investigate the influence of the motion frequency on the added mass and the radiation damping of the truncated cylinders with different geometric parameters. The present solutions can be used as a reliable benchmark for numerical solutions to water wave radiation by complicated structures.