scholarly journals Aerodynamic damping and fluid-structure interaction of blast loaded flexible structures

2011 ◽  
Author(s):  
M. Teich ◽  
N. Gebbeken
Keyword(s):  
Fluid Structure Interaction ◽  
Flexible Structures ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Aerodynamic Damping

Aerodynamic Damping and Fluid-Structure Interaction of Blast Loaded Flexible Structures

2011 ◽  
Vol 82 ◽  
pp. 491-496
Author(s):  
Martien Teich ◽  
Norbert Gebbeken ◽  
Martin Larcher
Keyword(s):  
Dynamic Response ◽  
Fluid Structure Interaction ◽  
Flexible Structures ◽  
Blast Loads ◽  
Damping Term ◽  
Damping Force ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Aerodynamic Damping ◽  
Compliant Systems

This paper analyses the e ects of air-structure interaction of systems subjectedto weak blast loads. While these coupling e ects are negligible for typical steel or concretestructures, they may dominate the dynamic response of lighter and more exible (compliant)systems like membranes, blast curtains or cable facades. For these light and exible systems,a classical decoupled analysis, i.e., neglecting the inuence of the surrounding air, might sig-ni cantly overestimate the deections and strains. However, we show that the coupling e ectscan be accounted for by basically adding a viscous aerodynamic damping force. We discussand compare two approaches how to obtain the aerodynamic damping term. With decreasingstructural sti ness and mass, the damping contribution of air increases signi cantly. The resultsof Hydrocode simulations are presented, and an outlook into further areas of research is given.

scholarly journals Fluid–structure interaction-induced oscillation of flexible structures in laminar and turbulent flows

2013 ◽  
Vol 715 ◽  
pp. 537-572 ◽  
Author(s):  
Jorge Pereira Gomes ◽  
H. Lienhart
Keyword(s):  
Turbulent Flows ◽  
Fluid Structure Interaction ◽  
Flexible Structures ◽  
Reynolds Numbers ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Flow Disturbances ◽  
Oscillation Modes ◽  
Excited Oscillation ◽  
Excitation Mechanisms

AbstractSelf-excitation of the motion of a structure has become a prominent aspect of engineering projects over recent years as designers are using materials at their limits, causing structures to become progressively lighter, more flexible and, therefore, prone to vibrate. Stimulated by the increasing interest in fluid–structure interaction (FSI) problems, this study investigated the instability and consequent FSI-induced self-excited oscillation of flexible structures in uniform flows at Reynolds numbers between $10$ and $1. 69\times 1{0}^{5} $. The investigations were performed in both water and a highly viscous syrup ($\nu = 1. 64\times 1{0}^{- 4} ~{\mathrm{m} }^{2} ~{\mathrm{s} }^{- 1} $) and considered three structures of different geometries. The results were conclusive in showing that the motion of the structure was characterized by a sequence of oscillation modes as a function of the characteristics of the structure and flow properties. In addition, it was possible to identify the self-excitation mechanisms as being of the instability-induced excitation (IIE) or movement-induced excitation (MIE) types. IIE was observed to be the most dominant mechanism of excitation at lower velocities and it was defined by a direct relation between the flow fluctuation and natural frequencies of the structure. For that reason, IIE was strongly determined by the geometry of the front body of the structure. At higher velocities, the amplitudes of the flow disturbances generated by the structure movement increased and excitations of the MIE type became predominant for all structures. The MIE mechanism was found to be weakly influenced by the shape of the structure but very sensitive to its dynamic characteristics and to the properties of the fluid, especially the Reynolds number.

scholarly journals Investigation of Fluid-Structure Interaction Induced Bending for Elastic Flaps in a Cross Flow

2020 ◽  
Vol 10 (18) ◽  
pp. 6177 ◽  
Author(s):  
Tayyaba Bano ◽  
Franziska Hegner ◽  
Martin Heinrich ◽  
Ruediger Schwarze
Keyword(s):  
Present Model ◽  
Fluid Structure Interaction ◽  
Flexible Structures ◽  
Three Dimensional ◽  
Cross Flow ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Numerical Investigations ◽  
Transient Simulations ◽  
Ansys Workbench

With the recent increase in the design of light and flexible structures, numerical investigations of fluid and structure together play a significant role in most engineering applications. Therefore, the current study presents an examination of fluid-structure interaction involving flexible structures. The problem is numerically solved by a commercial software ANSYS-Workbench. Two-way coupled three-dimensional transient simulations are carried out for the flexible flaps of different thicknesses in glycerin for a laminar flow and Reynolds number ranging from 3 < Re < 12. The bending line of the flaps is compared with experimental data for different alignments of the flaps relative to the fluid flow. The study reports the computation of the maximum tip-deflection and deformation of flaps fixed at the bottom and mounted normal to the flow. Additionally, drag coefficients for flexible flaps are computed and flow regimes in the wake of the flaps are presented. As well, the study gives an understanding on how the fluid response changes as the structure deforms and the model is appropriate to predict the behavior of thick and comparatively thinner flaps. The results are sufficiently encouraging to consider the present model for analyzing turbulent flow processes against flexible objects.

Forced Response Analyses of Mistuned Radial Inflow Turbines

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Thomas Giersch ◽  
Peter Hönisch ◽  
Bernd Beirow ◽  
Arnold Kühhorn
Keyword(s):  
Numerical Method ◽  
Fluid Structure Interaction ◽  
Industrial Applications ◽  
Forced Response ◽  
Blade Vibration ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Aerodynamic Damping ◽  
Radial Turbine ◽  
Spiral Casing

Radial turbine wheels designed as blade integrated disks (blisk) are widely used in various industrial applications. However, related to the introduction of exhaust gas turbochargers in the field of small and medium sized engines, a sustainable demand for radial turbine wheels has come along. Despite those blisks being state of the art, a number of fundamental problems, mainly referring to fluid-structure-interaction and, therefore, to the vibration behavior, have been reported. Aiming to achieve an enhanced understanding of fluid-structure-interaction in radial turbine wheels, a numerical method, able to predict forced responses of mistuned blisks due to aerodynamic excitation, is presented. In a first step, the unsteady aerodynamic forcing is determined by modeling the spiral casing, the stator vanes, and the rotor blades of the entire turbine stage. In a second step, the aerodynamic damping induced by blade vibration is computed using a harmonic balance technique. The structure itself is represented by a reduced order model being extended by aerodynamic damping effects and aerodynamic forcings. Mistuning is introduced by adjusting the modal stiffness matrix based on results of blade by blade measurements that have been performed at rest. In order to verify the numerical method, the results are compared with strain-gauge data obtained during rig-tests. As a result, a measured low engine order excitation was found by modeling the spiral casing. Furthermore, a localization phenomenon due to frequency mistuning could be proven. The predicted amplitudes are close to the measured data.

Forced Response Analyses of Mistuned Radial Inflow Turbines

2012 ◽  
Author(s):  
Thomas Giersch ◽  
Peter Hönisch ◽  
Bernd Beirow ◽  
Arnold Kühhorn
Keyword(s):  
Numerical Method ◽  
Fluid Structure Interaction ◽  
Industrial Applications ◽  
Forced Response ◽  
Blade Vibration ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Aerodynamic Damping ◽  
Radial Turbine ◽  
Spiral Casing

Radial turbine wheels designed as blade integrated disks (blisk) are widely used in various industrial applications. However, related to the introduction of exhaust gas turbochargers in the field of small and medium sized engines a sustainable demand for radial turbine wheels has come along. Despite those blisks are state of the art, a number of fundamental problems, mainly referred to fluid-structure-interaction and therefore to the vibration behavior, have been reported. Aiming to achieve an enhanced understanding of fluid-structure-interaction in radial turbine wheels a numerical method, able to predict forced responses of mistuned blisks due to aerodynamic excitation, is presented. In a first step the unsteady aerodynamic forcing is determined by modeling the spiral casing, the stator vanes and the rotor blades of the entire turbine stage. In a second step the aerodynamic damping induced by blade vibration is computed using a harmonic balance technique. The structure itself is represented by a reduced order model being extended by aerodynamic damping effects and aerodynamic forcings. Mistuning is introduced by adjusting the modal stiffness matrix based on results of blade by blade measurements that have been performed at rest. In order to verify the numerical method, the results are compared with strain-gauge data obtained during rig-tests. As a result a measured low engine order excitation was found by modeling the spiral casing. Furthermore a localization phenomenon due to frequency mistuning could be proven. The predicted amplitudes are close to measured data.

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