For a structure vibrating in a viscous fluid the modal damping ratio can be expressed as follows. A new method of determining acoustic added mass and. Fluidstructure interaction fsi is a multiphysics coupling between the laws that describe fluid dynamics and structural mechanics. Scaling of added mass and added damping of cylindrical. In order to calculate hydrodynamic pressure of piers with arbitrary crosssections under earthquake, a new added mass method is presented. The fem is applied to evaluate the dynamic blade stresses and deformations. Timedomain analysis of the hydroelastic response of. While these coupling e ects are negligible for typical steel or concretestructures, they may dominate the dynamic response of lighter and more exible compliantsystems like membranes, blast curtains or cable facades. Modelling of fluidstructure interaction effects of added mass. The method is designed and demonstrated for use in interactive 3d systems, where live sound synthesis is important. Bthe added damping the damping mechanism is complex phenomenon which depends on many factor associated to the fluid and structure parameters such as viscosity, types of fluid,the lift and drag forces, boundary conditions, structure mass and stiffness, fluid hammering, etc. The scheme is based on a generalized robin interface condition for the fluid pressure. Numerical investigation of added mass and hydrodynamic.
The scheme is stable irrespective of the socalled added mass effect and allows for conservative timestepping within the structure. Investigation of the added mass method for seismic design. Jeanfrancois sigrist fulfills the need for an introductive approach to the general concepts of fsi from the mathematical formulation to the physical interpretation of numerical simulations. Fluidstructure interaction fsi is the interaction of some movable or deformable structure with an internal or surrounding fluid flow. These phenomena increase fluidstructure interaction fsi related issues among. The added mass is generally described as a matrix which models the interaction of the elements of the mechanical structure via the fluid pressure fluctuations. In oscillatory interactions, the strain induced in the solid structure causes it to move such that the source of strain is reduced, and the. A stable added mass partitioned amp algorithm is developed for fluid structure interaction fsi problems coupling viscous incompressible flow and compressible elastic solids.
If you want to see how fluidsolid interactions work, and be able to use that knowledge, join us. Introduction an important notion in fluid structure interaction studies is that of added mass of mechanical systems vibrating in a liquid. I tried different approaches to model the silicone in the solid mechanics module. The hyperbolic system governing the solid is integrated using an explicit upwind godunov scheme. Influence of the added mass effect and boundary conditions. The added mass coefficient is not always unity but rather depends on the body shapes, the fluid viscosity, and the fluid compressibility.
Fluidstructure interaction analysis for hydrodynamic. Part of the cism international centre for mechanical sciences book series. Fluid structure interaction effect nacim mellel et al. Fluid structure interaction simulations in still air have been performed to assess added mass and added damping effects. An analysis is made of a new partitioned scheme for solving fluid structure interaction problems involving viscous incompressible flow and compressible elasticsolids. In many fluid structure interaction problems, the added mass, inertial mass, virtual mass, carried mass or induced mass is one of important interests.
This book provides with analytical tools for the analysis of the vibrations of. Computational methods for fluid structure interaction longman, 1994 116. In this paper, we propose a semiimplicit coupling scheme for the numerical simulation of fluid structure interaction systems involving a viscous incompressible fluid. Added mass and damping in fluid structure interaction by c. Planchard, global behaviour of large elastic tube bundle immersed in a fluid, comput. Investigation of added mass and damping coefficients of. For this reason, during the past 30 years and over most coupled fluid structural dynamic problems have been solved by simplifying them as weakly coupled problems provided that a hydrodynamic mass and a hydrodynamic damping are added to the original mass and damping of each structure under consideration, respectively, to take into account the. The added mass and the added damping are both proportional to the mass number. Fluid added mass, damping, and stiffness are highly relevant parameters to consider. The added mass coefficient c m is the ratio of the added mass to the displaced fluid mass m f. The fluidstructure interaction for multiple mem bers is significantly.
Modelling of fluidstructure interaction effects of. Shailendra 4, however, proposed a finite element analysis to determine only the added mass coefficient. It was concluded that immersion in water does not add significant damping to oil and gas pipework. These approaches are illustrated with examples arising from industrial or academic applications. Flowinduced vibration is a term to denote those phenomena associated with the response of structures placed in or conveying fluid flow. Proceedings of the asme 2015 pressure vessels and piping conference. An experimental investigation of added mass and damping in.
Fundamentals of fluidsolid interactions polytechnique. Fluid structure interaction analysis on vibrations of a rod exposed to axial flow 5 summary vibration on components caused by flow, so called flow induced vibrations, is an important area in many industrial fields, including the nuclear power. The fictitious pressure method involves modification of the fluid solver whereas the fictitious mass and damping methods modify the structure solver. Proceedings of the asme 2002 international mechanical engineering congress and exposition. Adaptive time stepping for fluidstructure interaction. In addition, the hydrodynamic damping effects is remarkably affected by the interplay of geometric and dynamic parameters. In other words, the added mass can be imaged as a virtual mass added to the structure resulting from the acceleration of the surrounding fluid. Fluidstructure interactionfsi, hydrodynamic mass, hydrodynamic damping, weakly coupling, strongly coupling, oneway separate analysis, twoway. It was necessary to include appropriate added mass coefficients in the computer simulation for both the pipe and the support system. Fluidstructure interactions can be stable or oscillatory. This happens all the time, around you when leaves flutter in the wind, inside you when your heart beats, above you when wings of a plane vibrate, under the sea. Added mass formulation for fluidstructure interaction.
A new added mass method for fluidstructure interaction. An important notion in fluidstructure interaction studies is that of added mass. Modeling fluidstructure interaction technical knowledge. The key contribution of this work is to enhance the sound synthesis equation in the rigidbody audio pipeline to account for the fluid force on an object at the fluid structure. This addedmass partitioned amp algorithm remains stable, without subiterations, for light and even zero mass rigid bodies when addedmass and viscous addeddamping effects are large. This model contributes to a better understanding of the physical coupling phenomena and can be used for the validation of more complex numerical models. Added mass and hydrodynamic damping play significant roles in fluidstructure interaction fsi in hydraulic turbines. The added mass effect also explains that the closer to a rigid. It is important to estimate both added mass and radiation damping of floating artificial base, which is floating structure, in fluid structure interaction problem. The new scheme is stable, without subtimestep iterations, even for light solids when added mass and added damping effects are large. Fluid structure interaction analysis for hydrodynamic parameters in semi submerged axisymmetric buoy. Added mass can reduce natural frequencies, while hydrodynamic damping could result in a higher amplitude decay speed of the vibration. Introduction an important notion m fluidstructure interaction studies is that of added mass of mechanical systems vibrating in a liquid. To accomplish this, the relation between fundamental frequency reduction rate and the ratio of added mass to structural mass.
Proceedings of the eighth international symposium on practical design of ships and other floating structures, 1621 september 2001, shanghai, china, vol. The viscous effect on the mechanical system can then be represented by a damping term of type timeconvolution. Planchard this paper is concerned with the added mass matrix for a mechanical structure vibrating in an incompressible liquid. The new scheme is stable, without subtimestep iterations, even for light solids when added mass and added damping. However, i still try to make the fluid structure interaction working ie. Vibration and damping of hydrofoils in uniform flow etda. This phenomenon is characterized by interactions which can be stable or oscillatory between a deformable or moving structure and a surrounding or internal fluid flow.
To this end, the mathematical formulation of a simple fluid structure interaction problem is introduced. This added mass partitioned amp algorithm remains stable, without subiterations, for light and even zero mass rigid bodies when added mass and viscous added damping effects are large. The effects of fluid structure interaction are included by superimposing the added mass and hydrodynamic damping matrices to the material mass and damping matrices in the equilibrium equation of motion. If we consider now the dimensional quantities, you remember that we had an added mass that was proportional to the fluid density rho. Flow induced vibration of circular cylindrical structures. Introduction the fluid structure interaction is a subject of interest in the areas of propellers design and wind and tidal technologies 1,2,3. N2 considerable research activities in vibration and seismic analysis for various fluid structure systems have been carried out in the past two decades. Subsequently, based on the mentioned studies, an added mass formulation is derived for a specific mems micro electro mechanical system. The arch dam, which is an idealized model itself, has a total height of 220 meters. Influence of the fluidstructure interaction on the vibrations of. Fluidstructure interactions involving slender structures and axial flow are illustrated by three typical examples from engineering practice.
Is the usage of 2% damping ratio for the first mode of all metallic structures justified. This paper is concerned with the added mass matrix for a mechanical structure vibrating in an incompressible liquid. The added mass and damping coefficients based on the multipole expansion by wu, g. The added effects such as added mass and damping acting from the fluid on a structure, strongly affect the dynamic response of the structure submerged in water. As a result, by the argand diagram, the stability analysis is investigated.
It is also an ideal text for graduate and seniorlevel undergraduate courses in computational fluid mechanics and computational fsi. It is what happens when the motions of a fluid and of a solid are somehow coupled. In the present study, the authors propose a simple and efficient method to specify fluid force coefficients of an oscillating object in stationary fluid. Natural frequencies and damping of a fullscale pipe loop. Cism international centre for mechanical sciences, vol 557. In 1828, the concept of hydrodynamic mass or added mass was proposed first by. All calculations of the added mass and damping were done analytically and therefore needed to deal with complex mathematics. We find that the added mass effect is affected by the presence of the flanges, which results into larger fluid entrainment during the lamina oscillation. This is why we called the course fundamentals of fluid solid interactions. In the book of blevins 8 in chapter 10 the vibrations of a pipe containing a fluid flow. Added mass is a common issue because the object and surrounding fluid cannot occupy the same physical space simultaneously. If you want to see how fluid solid interactions work, and be able to use that knowledge, join us.
A novel technique for the measurement of blade damping using. When a floating artificial base shows elastic behavior, its damping contains both structural damping and radiation damping. For the case above, the displaced fluid mass is d 2 4 and therefore the added mass coefficient is 1. In addition to the stiffness and damping, the added mass has been studied for simple objects5 and complex structures, such as pumps6,7 and offshore structures. Furthermore, interaction between fluid and structure is calculated by a staggered scheme, which will become divergent if the added mass effect is strong. A stable partitioned algorithm is developed for fluidstructure interaction fsi problems involving viscous incompressible flow and rigid bodies. Thomas, on the added mass, damping stiffness matrices for an elastic structure placed in a potential crossflow, j.
Music hello, and welcome to our fluid structures interaction lab. Added mass and damping in fluidstructure interaction sciencedirect. A stable partitioned fsi algorithm for rigid bodies and. Modelling of fluidstructure interaction effects of added mass, damping and. During an earthquake, lock gates are subjected to additional pressure since the water contained in the chamber is put into motion by the earthquake. Fluid structure interaction of a vibrating circular plate in. Problems involving vibrating solids in a fluid medium are especially common due to the finite rigidity of the submerged bodies blades and a wide array. Addedmass and viscousdamping forces acting on various. Added mass and hydrodynamic damping play significant roles in fluid structure interaction fsi in hydraulic turbines. Finite amplitude oscillations of flanged laminas in. Fluid structure interaction problems can be solved by coupling a structure solver to a fluid solver and. Fluidstructure interactionfsi, hydrodynamic mass, hydrodynamic damping, weakly coupling, strongly coupling, oneway separate analysis, two way. Added mass and damping in fluidstructure interaction. Robin based semiimplicit coupling in fluidstructure.
Methods and applications is a comprehensive reference for researchers and practicing engineers who would like to advance their existing knowledge on these subjects. We analyze all fictitious methods for simplified problems and obtain explicit expressions for the optimal reduction factor. For complex structures, they can be obtained using approximate procedures like the galerkin method of weighted residuals. Arbitrary lagrangianeulerian and fluidstructure interaction. A master of science thesis in mechanical engineering by afsoun koushesh entitled, added mass formulation for fluid structure interaction, submitted in may 2016. An addedmass partition algorithm for fluidstructure. For example, the added mass of a twodimensional circular cylinder in an infinite and quiescent fluid and the resulting inertial fluid force are expressed as follows. The added damping decreases with the stokes number. Added mass and damping in fluidstructure interaction it is shown in particular that this matrix does not depend on viscosity and, from this fact, can be calculated as if the fluid is perfect.
For a propeller vibrating in a fluid, the added mass and damping coefficients characterize the hydrodynamic forces and moments acting on the propeller, which are of great importance for evaluation of the vibration behaviors of submerged propellers. This book provides the fundamental basics for solving fluid structure interaction problems, and describes different algorithms and numerical methods used to solve problems where fluid and structure can be weakly or strongly coupled. Added mass for the case of unsteady motion of bodies underwater or unsteady flow around objects, we must consider the additional effect force resulting from the fluid acting on the structure when formulating the system equation of motion. The interaction with the water is accounted for by using added mass technique and for comparison reasons with a fully modelled reservoir too. In this paper, fully coupled fluid structure interaction simulations are applied to give insight into the complex physical phenomenon of horizontal wide span membrane roofs which are stabilized only by selfweight.
Aerodynamic damping and fluidstructure interaction of blast. Modelling of fluidstructure interaction effects of added. In fluid mechanics, added mass or virtual mass is the inertia added to a system because an accelerating or decelerating body must move or deflect some volume of surrounding fluid as it moves through it. May 02, 20 however, i still try to make the fluid structure interaction working ie. The effect of the surrounding water on the damping was measured but found to be insignificant. Pdf added mass and damping in fluidstructure interaction.
Pdf this paper is concerned with the added mass matrix for a mechanical structure vibrating in an incompressible liquid. A stable addedmass partitioned amp algorithm for elastic. Is damping coefficient dependent on shape of the body. The authors derive a new coupling model taking into account fluid structure interaction fsi and aerodynamic damping resulting from the surrounding air. An introduction to finite element coupling fulfils the need for an introductive approach to the general concepts of finite and boundary element methods for fsi, from the mathematical formulation to the physical interpretation of numerical simulations. In general, the fluid reaction forces can be expressed in terms of added mass and added damping to the corresponding values of the isolated structure i. Based on the authors experience in developing numerical codes for industrial applications in shipbuilding and in. Fluid structure interaction fsi fsi applications involve coupling of fluid dynamics and structure mechanics disciplines fluid flow exerts hydrodynamic forces on a structure and deforms andor translates the structure fluid flow can also modify thermal stresses within the structure. Is damping coefficient of 1dof system simple spring mass damper system dependent on the shape of the mass. Influence of damping and different interaction modelling on a. The added mass and damping of propellers caused by the fluid are important parameters in the vibration analysis or the fluid structure interaction analysis of the marine propulsion shafting. The scope and special emphasis of this book are discussed, followed by a description of the content of each chapter of the book, as well as the contents of volume 2. This paper analyses the e ects of air structure interaction of systems subjectedto weak blast loads. On the relationship between added mass and added damping.
There are so many phenomena and so many models that we need to work together on the basic mechanisms. Fluid loaded mass, hydrodynamic stiffness and hydrodynamic damping parameters for the first two bending and torsional modes of the cantilever blade are extracted from coupled structure single input, single output siso modal analysis. The present paper is concerned with the development of a numerical method for predicting the added mass and damping coefficients of a. In that session, we are going to focus on added mass and added damping. More specifically, the terra covers those cases in which an interaction develops between fluid dynamic forces and the inertia, damping or elastic forces in the structures. The model is implemented as an analytical procedure for simple structures. Also the damping of the circular plate for different water levels is measured. A stable partitioned algorithm is developed for fluid structure interaction fsi problems involving viscous incompressible flow and rigid bodies.
The equations for the fluid are integrated using an implicitexplicit imex fractionalstep scheme whereby. The added mass and damping in fsi had been calculated by c. Fluidstructure interaction problems with strong added. In some cases, the fluid structure interaction is so complex that vibration frequencies depend on both the structure and the fluid.
As you have seen in lectures, both can significantly effect the dynamics of a solid moving in a fluid domain. Tendency of damping ratio of floating artificial base by. We calculate the added mass, added damping, added stiffness analytically by fluid structure interaction analysis. In practical design of ships and other floating structures. Computation of the added mass matrix using a panel method. An experimental investigation of added mass and damping in submerged pipework.
1019 1383 323 566 823 640 182 1320 890 1427 982 762 191 63 1160 1125 829 1062 860 194 298 614 1293 489 1056 387 513 1079 89 1359 1374 637 1024 921 837 690 651 1207 973 1279 35 874 908