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Transition modelling in blade cascades
Straka, P. ; Příhoda, Jaromír
A modified algebraic model of the laminar/turbulent bypass transition was implemented into the in-house numerical code for the simulation of 2D compressible turbulent flow using the RANS equations closed by the two-equation k-omega TNT turbulence model. The model was verified by the ERCOFTAC test cases for various boundary-layer flows and applied for the simulation of the transitional flow in turbine blade cascades.
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Awakening of traveling wave of rotor blade wheel by multipoint electro-magnetic excitation
Pešek, Luděk ; Vaněk, František ; Veselý, Jan ; Bula, Vítězslav ; Cibulka, Jan
The analytical expressions for description of traveling waves in rotating blade wheels are presented in the contribution. Both axis-symmetric case of the wheel characterized by multiple eigenvalues and the wheel with imperfection causing the split of this multiplicity are discussed herein. These expressions serve, based on the affinity to the traveling waves, for finding the optimal distribution and time dependences of the excitation forces of the multipoint electromagnetic excitation. The theoretical findings are verified numerically and experimentally on the case of free supported ring in a non-rotating state.
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Damping of turbine blades by means of friction elements
Půst, Ladislav ; Pešek, Luděk ; Veselý, Jan ; Radolfová, Alena
Theoretical analysis of vibrations of double beam system with a friction connection eccentrically situated on beams ends is provided in the first part of contribution. It is shown that the eccentricity of contact changes the type of relative contact motion, increases the damping of entire system, changes forms of beam deformation and increases resonance frequencies. Detuning of beams can also increase efficiency of vibration’s quenching. Experimental verification of this property is described in the second part of contribution.
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