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Self-excited vibration of a palisade in 2D subsonic, transonic and supersonic flow

100%

Rządkowski R. , Kovalyov A.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

2000

tom Vol. 4, No 1

49-80

In recent years coupled fluid-structure problems have appeared. The computational method used to solve this problem was based on a time-marching algorithm, so it was natural to consider a time domain flutter analysis method. The time domain method of flutter analysis is based on the simultaneous integration in time of the equation of motion for the structure and the fluid. The flow model is capable of representing 2D flows over a wide Mach number range from low subsonic to supersonic, including transonic flows. The aerodynamic model fully accounts for blade thickness and camber and the angle-of-attack effects. The unsteady Euler equations are integrated by using the explicit monotonous second-order accurate Godunov scheme. The blade is modelled on the basis of extended beam theory including a bending-bending-torsional vibration and also by the simple two-degree of freedom model. The equation of motion is obtained by using the extended Hamilton's principle and the Ritz method. The direct integration method is used to find a solution of the coupled fluid-structure problem. In this work the comparison of numerical and experimental results is presented for the first and fourth standard configurations.

2D inviscid flutter of the mistuned Fourth and First Standard Configuration

100%

Rządkowski R. , Kovalyov A.

tom nr 112

139--154

The trend in aviation engines with high specific power and, correspondingly, high aerodynamic loads leads to the problem of aeroelastic behaviour of blades not only in compressors and fans, but also in turbines. Investigations of aeroelastic of the blades in dependence of structural mistuning are presented. A numerical calculation method for unsteady aerodynamic characteristics of oscillating blade cascades under the action of unstable loads is based on solution of the coupled fluid-structure problem, in which the aerodynamic and structural dynamic equations are integrated simultaneously in time, thus providing the correct formulation of a coupled problem, as the interblade phase angle, at which a stability (instability) would occur, is a part of solution. The ideal gas flow around multiple stage passages (with periodicity on the whole annulus) is described by the unsteady 2D Euler equations in conservative form, which are integrated by using the explicit monotonous second order accurate Godunov-Kolgan finite-volume scheme on the moving grid. The blade is modelled by a very simple two degrees of freedom discrete model. In this model cascade performs the torsional and the bending oscillations under the given law. The aeroelastic behaviour of the blades in the unsteady aerodynamic flow is calculated for the mistuned blades assemblies of the Fourth and First Standard Configurations. The computational domain of the unsteady flow can not be restricted to the single blade passage. The results in the time domain analysis show the beneficial influence of the mistuning of the bending mode in comparison to the torsional mode. The dynamic properties of the mistuned systems are dependent on the way of coupling of the blades, whether it is either aerodynamic or mechanical.

Comparison of the 2d and 3d models of flutter of a palisade in an inviscid flow

80%

Rządkowski R. , Gnesin V. , Kovalyov A.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

1999

tom nr 115

349--356

In recent years the works of the coupled fluid-structure problems appeared. The computational method used to solve this problem was based on a time-marching algorithm, so it was natural to consider a time domain flutter analysis method. The time domain method of flutter analysis is based on the simultaneous integration in time of the equation of motion for the structure and the fluid. In this work the comparison of the 2D and 3D Flutter results for the turbine cascade (IV Configuration) is shown. It was observed that the negative aerodamping coefficient calculated for the harmonic oscillation are not sufficient condition for growing oscillation during fluid-structure interaction.