Experimental Damping Behavior of Strongly Coupled Structure and Acoustic Modes of a Rotating Disk With Side Cavities

Abstract High cycle fatigue is a continuous research topic within the turbomachine community. One field of the investigations is the fluid-structure interaction of 2-D impellers, which can be simplified as disks with their surrounding side cavities. In modern machines the pressure ratios tend to increase along with pressure fluctuations and the excitation potential on the impellers. The vibrational interactions between side cavities, filled with high pressure fluid, and the disk structure play an important role in machine design. However, they are not fully understood, yet. Vibrations at frequencies that have been uncritical at lower pressure levels could become critical at higher pressure levels. Additionally, coupling effects between fluid and structure are becoming stronger at higher fluid densities. For a safe and reliable design, the excitation and the damping mechanism of coupled modes has to be better understood. This paper summarizes the test rig setup and focuses on one of the main findings of an extensive experimental research project, which investigated the fluid-structure interaction of a disk with side cavities, at the University of Duisburg-Essen. The focus lays on the damping behavior of strongly coupled acoustic and structure modes. Measurement results gathered at the aeroacoustic test rig are presented. The results show the influence of fluid pressure variations on the damping behavior of acoustic modes. Therefore, the response functions of some selected acoustic modes are evaluated with the half-width method. Compared to the weakly coupled structure mode, the damping of the strongly coupled structure mode is some orders higher at atmospheric pressure conditions. The damping ratio decreases with an increasing pressure level, however still remains some orders higher, than the damping of weakly coupled structure modes.

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Damping Behavior of Acoustic Dominant Modes in an Aeroacoustic Test Rig Representing a Simplified Geometry of a High Pressure Radial Compressor

Volume 7C: Structures and Dynamics ◽

10.1115/gt2018-76629 ◽

2018 ◽

Author(s):

Botond Barabas ◽

Dieter Brillert ◽

Hans Josef Dohmen ◽

Friedrich-Karl Benra

Keyword(s):

High Pressure ◽

Damping Ratio ◽

Pressure Fluctuations ◽

Fluid Pressure ◽

Test Rig ◽

Coupled Modes ◽

Acoustic Modes ◽

Damping Behavior ◽

Weakly Coupled ◽

Reliable Design

Pressure ratios of modern high pressure radial compressors tend to increase along with pressure fluctuations and the excitation potential on the impellers. The vibrational interactions between side cavities, filled with high pressure fluid, and the impeller structure play an important role in designing a machine for reliable operation. However, they are not yet fully understood. Vibrations at frequencies that have been uncritical at lower pressure levels could become critical at a higher pressure level. Additionally, coupling effects between fluid and structure are becoming stronger at higher fluid densities. For a safe and reliable design, the excitation and the damping mechanism of coupled modes has to be better understood. To understand the interaction, especially regarding the damping behavior, of coupled structure and acoustic modes, a comprehension of the behavior of the uncoupled or weakly coupled modes is required. The structural damping ratio is very small and it has been analyzed in existing literature extensively. The damping behavior of uncoupled acoustic modes, however, is not yet well investigated. This paper focuses on the damping behavior of acoustic modes that are weakly coupled to structure modes. Measurement results gathered at the aeroacoustic test rig at the University of Duisburg-Essen are presented. The results show the influence of fluid pressure variations on the damping behavior of acoustic modes. Therefore, the response functions of some selected acoustic modes are evaluated with the Peak-to-Peak method. In general, the damping decreases with increasing fluid pressure. Furthermore, a relationship of the damping ratio, the kinematic viscosity, and the natural frequency of the acoustic modes has been detected.

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Cell-Based Smoothed Finite-Element Framework for Strongly Coupled Non-Newtonian Fluid–Structure Interaction

Journal of Engineering Mechanics ◽

10.1061/(asce)em.1943-7889.0001968 ◽

2021 ◽

Vol 147 (10) ◽

pp. 04021062

Author(s):

Tao He

Keyword(s):

Finite Element ◽

Newtonian Fluid ◽

Fluid Structure Interaction ◽

Fluid Structure ◽

Strongly Coupled ◽

Structure Interaction

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Dynamics of a Free Heaving and Prescribed Pitching Hydrofoil in a Turbulent Flow, With a Fluid-Structure Interaction Approach

Volume 4: Fluid-Structure Interaction ◽

10.1115/pvp2018-84636 ◽

2018 ◽

Author(s):

P. Brousseau ◽

M. Benaouicha ◽

S. Guillou

Keyword(s):

Fluid Structure Interaction ◽

Vertical Displacement ◽

Rotational Displacement ◽

Fluid Structure ◽

Strongly Coupled ◽

Structure Interaction ◽

Maximum Angle ◽

High Maximum ◽

Oscillating Foil ◽

Interaction Approach

This paper deals with the dynamics of an oscillating foil, describing a free heaving (vertical displacement) and prescribed pitching (rotational displacement) movement which is computed from its position in two different ways. A fluid-structure interaction approach is chosen, as the physics of the flow and the structure are strongly coupled. The flow is unsteady, turbulent and incompressible. The pressure/velocity problem is solved using SIMPLEC scheme. First, the pitching movement is considered as a given continuous function of the hydrofoil heaving position. Second, the pitching motion is performed alternately at the end of each heave cycle. For each case, two maximum angles of attack and one heaving amplitudes are studied. Preliminary results showed that a high maximum angle of attack generates more lift hydrodynamics force, but also requires more energy to perform the rotation of pitch.

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Study on Fluid-Structure Interaction of Flexible Membrane Structures in Wind-Induced Vibration

Shock and Vibration ◽

10.1155/2021/8890593 ◽

2021 ◽

Vol 2021 ◽

pp. 1-10

Author(s):

Fangjin Sun ◽

Donghan Zhu ◽

Tiantian Liu ◽

Daming Zhang

Keyword(s):

Projection Method ◽

Fluid Structure Interaction ◽

Initial Pressure ◽

Projection Methods ◽

Accurate Solution ◽

Membranous Structure ◽

Fluid Structure ◽

Strongly Coupled ◽

Structure Interaction ◽

Modified Projection Method

A strongly coupled monolithic method was previously proposed for the computation of wind-induced fluid-structure interaction of flexible membranous structures by the authors. How to obtain the accurate solution is a key issue for the strongly coupled monolithic method. Projection methods are among the commonly used methods for the coupled solution. In the work here, to impose initial pressure boundary conditions implicitly defined in the original momentum equations in classical projection methods when dealing with large-displacement of membranous structures, a modified factor is introduced in corrector step of classical projection methods and a new modified projection method is obtained. The solution procedures of the modified projection method aimed at strongly coupled monolithic equations are given, and the related equations are derived. The proposed method is applied to the computation of a two-dimensional fluid-structure interaction benchmark case and wind-induced fluid-structure interaction of a three-dimensional flexible membranous structure. The performance and efficiency of the modified projection method are evaluated. The results show that the modified projection methods are valid in the computation of wind-induced fluid-structure interaction of flexible membranous structures, with higher accuracy and efficiency compared with traditional methods. The modified value has little effects on the computation results whereas iteration times has significant effects. Computation accuracy can be improved greatly by increasing iteration times with less increase in computation time and little effects on stability with the modified projection method.

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Numerical Investigation of Hydroelastic Response of a Three-Dimensional Deformable Hydrofoil

Progress in Marine Science and Technology - HSMV 2020 ◽

10.3233/pmst200029 ◽

2020 ◽

Author(s):

Saeed Hosseinzadeh ◽

Kristjan Tabri

Keyword(s):

Pressure Coefficient ◽

Fluid Structure Interaction ◽

Three Dimensional ◽

Leading Edge ◽

Elastic Response ◽

Fluid Structure ◽

Strongly Coupled ◽

Structure Interaction ◽

Lift And Drag ◽

Hydroelastic Response

The present study is concerned with the numerical simulation of Fluid-Structure Interaction (FSI) on a deformable three-dimensional hydrofoil in a turbulent flow. The aim of this work is to develop a strongly coupled two-way fluid-structure interaction methodology with a sufficiently high spatial accuracy to examine the effect of turbulent and cavitating flow on the hydroelastic response of a flexible hydrofoil. A 3-D cantilevered hydrofoil with two degrees-of-freedom is considered to simulate the plunging and pitching motion at the foil tip due to bending and twisting deformation. The defined problem is numerically investigated by coupled Finite Volume Method (FVM) and Finite Element Method (FEM) under a two-way coupling method. In order to find a better understanding of the dynamic FSI response and stability of flexible lifting bodies, the fluid flow is modeled in the different turbulence models and cavitation conditions. The flow-induced deformation and elastic response of both rigid and flexible hydrofoils at various angles of attack are studied. The effect of three-dimension body, pressure coefficient at different locations of the hydrofoil, leading-edge and trailing-edge deformation are presented and the results show that because of elastic deformation, the angle of attack increases and it lead to higher lift and drag coefficients. In addition, the deformations are generally limited by stall condition and because of unsteady vortex shedding, the post-stall condition should be considered in FSI simulation of deformable hydrofoil. To evaluate the accuracy of the numerical model, the present results are compared and validated against published experimental data and showed good agreement.

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A Hybrid Numerical Model to Address Fluid Elastic Structure Interaction

Volume 7: Ocean Engineering ◽

10.1115/omae2016-54161 ◽

2016 ◽

Author(s):

Manoj Kumar Gangadharan ◽

Sriram Venkatachalam

Keyword(s):

Numerical Model ◽

Fluid Structure Interaction ◽

Breaking Waves ◽

Elastic Structure ◽

Navier Stokes ◽

Breaking Wave ◽

Ocean Engineering ◽

Fluid Structure ◽

Strongly Coupled ◽

Structure Interaction

Hydroelasticity is an important problem in the field of ocean engineering. It can be noted from most of the works published as well as theories proposed earlier that this particular problem was addressed based on the time independent/ frequency domain approach. In this paper, we propose a novel numerical method to address the fluid-structure interaction problem in time domain simulations. The hybrid numerical model proposed earlier for hydro-elasticity (Sriram and Ma, 2012) as well as for breaking waves (Sriram et al 2014) has been extended to study the problem of breaking wave-elastic structure interaction. The method involves strong coupling of Fully Nonlinear Potential Flow Theory (FNPT) and Navier Stokes (NS) equation using a moving overlapping zone in space and Runge kutta 2nd order with a predictor corrector scheme in time. The fluid structure interaction is achieved by a near strongly coupled partitioned procedure. The simulation was performed using Finite Element method (FEM) in the FNPT domain, Particle based method (Improved Meshless Local Petrov Galerkin based on Rankine source, IMPLG_R) in the NS domain and FEM for the structural dynamics part. The advantage of using this approach is due to high computational efficiency. The method has been applied to study the interaction between breaking waves and elastic wall.

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