A modal approach for coupled fluid structure computations of wing flutter

2016 ◽  
Vol 231 (1) ◽  
pp. 72-81 ◽  
Author(s):  
Jize Zhong ◽  
Zili Xu
Keyword(s):  
Computing Time ◽  
Elastic Solid ◽  
Mode Shapes ◽  
Mesh Deformation ◽  
Fast Calculation ◽  
Modal Approach ◽  
Fluid Structure ◽  
Wing Flutter ◽  
Flutter Boundary ◽  
Nodal Displacements

In this paper, a modal approach for the fast calculation of flow mesh deformation around a wing is developed based on the elastic solid method of dynamic mesh. The flow mesh domain is assumed to be a pseudo elastic solid. The displacement of the wing and the pseudo elastic solid is continuous at the fluid structure interface. Considering the condition of displacement continuity, the governing equation for the vibration of the wing with the pseudo elastic solid together is derived. The frequencies and mode shapes of the wing and the pseudo elastic solid are computed. Then the nodal displacements for the wing and the flow mesh are computed using modal superposition. The flutter boundary of the AGARD Wing 445.6 is predicted using the present modal approach by considering the first four modes of the wing. The calculated results compare well with the experimental data. The computing time is reduced by 54.8% compared with the pre-existing elastic solid method.

A reduced mesh movement method based on pseudo elastic solid for fluid–structure interaction

2017 ◽  
Vol 232 (6) ◽  
pp. 973-986
Author(s):  
Jize Zhong ◽  
Zili Xu
Keyword(s):  
Computing Time ◽  
Fluid Structure Interaction ◽  
Elastic Solid ◽  
Continuity Condition ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Wing Flutter ◽  
Mesh Movement ◽  
Nodal Displacements ◽  
Low Order

A reduced mesh movement method based on pseudo elastic solid is developed and applied in fluid–structure interaction problems in this paper. The flow mesh domain is assumed to be a pseudo elastic solid. The vibration equation for the structure and the pseudo elastic solid together is derived by applying the displacement continuity condition on the fluid–structure interface. Considering that the actual fluid–structure coupled vibration for structures often appears to be associated with low-order modes, the nodal displacements for the structure and the flow mesh can be computed using the modal superposition of a few low-order modes. Coupled fluid–structure computations are performed for flutter problems of a beam and wing 445.6 using the present method. The calculated results are consistent with the data reported in other references. The computing time is reduced by 65.5% for the beam flutter and 54.8% for the wing flutter compared with the pre-existing elastic solid method.

Fluid-Structure Interaction Using a Modal Approach

2011 ◽  
Author(s):  
F. Debrabandere ◽  
B. Tartinville ◽  
Ch. Hirsch ◽  
G. Coussement
Keyword(s):  
Fluid Structure Interaction ◽  
Axial Compressor ◽  
Linear Structure ◽  
Mode Shapes ◽  
Order Model ◽  
Modal Approach ◽  
Fluid Structure ◽  
Flow Solver ◽  
Reduced Order ◽  
Structure Interaction

A new method for Fluid-Structure Interaction (FSI) predictions is here introduced, based on a Reduced-Order Model (ROM) for the structure, described by its mode shapes and natural frequencies. A linear structure is assumed as well as Rayleigh damping. A two-way coupling between the fluid and the structure is ensured by a loosely-coupling staggered approach: the aerodynamic loads computed by the flow solver are used to determine the deformations from the modal equations, which are sent back to the flow solver. The method is firstly applied to a clamped beam oscillating under the effect of von Karman vortices. The results are compared to a full-order model. Then a flutter application is considered on the AGARD wing 445.6. Finally, the modal approach is applied to the aeroelastic behavior of an axial compressor stage. The influence of passing rotor blade wakes on the downstream stator blades is investigated.

Fluid–Structure Interaction Using a Modal Approach

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
F. Debrabandere ◽  
B. Tartinville ◽  
Ch. Hirsch ◽  
G. Coussement
Keyword(s):  
Fluid Structure Interaction ◽  
Axial Compressor ◽  
Linear Structure ◽  
Mode Shapes ◽  
Order Model ◽  
Modal Approach ◽  
Fluid Structure ◽  
Flow Solver ◽  
Reduced Order ◽  
Structure Interaction

A new method for fluid‐structure interaction (FSI) predictions is here introduced, based on a reduced-order model (ROM) for the structure, described by its mode shapes and natural frequencies. A linear structure is assumed as well as Rayleigh damping. A two-way coupling between the fluid and the structure is ensured by a loosely coupling staggered approach: the aerodynamic loads computed by the flow solver are used to determine the deformations from the modal equations, which are sent back to the flow solver. The method is first applied to a clamped beam oscillating under the effect of von Karman vortices. The results are compared to a full-order model. Then a flutter application is considered on the AGARD wing 445.6. Finally, the modal approach is applied to the aeroelastic behavior of an axial compressor stage. The influence of passing rotor blade wakes on the downstream stator blades is investigated.

A time-space synchronized fluid-structure coupling algorithm for the prediction of wing flutter

2017 ◽  
Vol 232 (5) ◽  
pp. 922-931
Author(s):  
Jize Zhong ◽  
Zili Xu
Keyword(s):  
Time Synchronization ◽  
Computing Time ◽  
Dynamic Mesh ◽  
Time Step ◽  
Fluid Structure ◽  
Wing Vibration ◽  
Time Space ◽  
Flutter Boundary ◽  
Coupling Algorithm ◽  
Fast Dynamic

A fast dynamic mesh technology by our research group has been applied in the time synchronized fluid-structure coupling. It is found that flow mesh update after the convergent calculation of the flow will induce excessive iterations in the computation of flow increasing the computing time of fluid-structure coupling. To reduce the computing time, a time-space synchronized fluid-structure coupling algorithm was developed in this paper based on the pre-existing time synchronized method and the fast dynamic mesh technology. The wing vibration and flow mesh deformation were computed using the fast dynamic mesh technology after each iteration in the calculation of the flow. Namely, the flow and the wing vibration were solved in space synchronization. The calculating convergence of the flow and the wing vibration were both achieved through iterations every time step. Namely, the flow and the wing vibration were solved in time synchronization. Thus, the flow and the wing vibration are coupled both in time and space synchronization. The flutter boundary of wing 445.6 was predicted using the present algorithm. The calculated results compare well with the experimental data and the computing time was almost reduced by 75%.

Applications of an Inviscid Q3D Linearized Flow Solver Towards the High Operating Line Flutter Region of a Transonic Fan

1998 ◽  
Author(s):  
Tomas J. Börjesson ◽  
Torsten H. Fransson
Keyword(s):  
Steady State ◽  
Three Dimensional ◽  
Mode Shapes ◽  
Flow Solver ◽  
Operating Line ◽  
Flutter Boundary ◽  
Euler Model ◽  
Transonic Fan ◽  
Phase Angles ◽  
Operating Points

The capabilities of an inviscid quasi three-dimensional linearized unstructured flow solver to correctly predict the stall flutter limit, flutter modes and critical inter-blade phase angles on a transonic rotating shroudless fan model where experimental data exist have been investigated. Three operating points were chosen for investigation at 70% and 95% speed. At 70% speed two points were investigated: one close to the torsional flutter boundary (at the intermediate operating line) and one at the flutter boundary. The 95% speed point was at the flexural flutter boundary. Steady state and unsteady calculations were made at several stream sections per operating point. At each stream section unsteady calculations were performed over the entire range of inter-blade phase angles with different mode shapes (real mode, rigid torsion and rigid bending) at different frequencies. Thus the model was “provoked” with “unphysical” mode shapes and frequencies to be compared to the unsteady solution obtained with the mode shapes and frequencies observed from the experiments. Furthermore all unsteady calculations were made with different mesh densities and solutions from different “tuned” and “untuned” steady-state solutions. The main conclusion of the validation of the inviscid Q3D Euler model on the Fan C Model Rotating Rig is that the model generally predicts flutter, flutter modes and the critical inter-blade phase angles to be close to the experimentally determined ones.

Importance of Enclosed Gas for Modal Analysis of Space Inflatable Structure

2014 ◽  
Vol 1016 ◽  
pp. 244-248
Author(s):  
Fei Liu ◽  
Wei Liang He
Keyword(s):  
Modal Analysis ◽  
Natural Frequencies ◽  
Fluid Structure Interaction ◽  
Mode Shapes ◽  
Follower Load ◽  
Nonlinear Finite Element Method ◽  
Load Effect ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Structure Research

The stress distribution and modal characteristics of a space inflatable torus is investigated using the nonlinear finite element method. This paper focused on the effect of enclosed air on the modal analysis of the torus, including the effect of follower pressure load and the effect of the interaction between the enclosed air and the torus structure. Research shows that follower pressure stiffness significantly reduces the natural frequencies and changes mode shapes order. The fluid-structure interaction obviously reduces the natural frequencies, and the in-plane translation mode is observed. Follower pressure stiffness has no effect on the in-plane translation mode. Fluid-structure interaction decreases the natural frequencies of the modal considering the follower load effect, but it does not change mode shapes order. The effect of enclosed gas seriously reduces the natural frequencies, changes mode shapes order, and produces the in-plane translation mode.

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